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Research on the Transmission of Disease in Airports and on Aircraft (2010)

Chapter: SESSION 5: Policies and Planning to Minimize the Spread of Disease

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Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
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Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
×
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Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
×
Page 45
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Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
×
Page 46
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Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
×
Page 47
Page 48
Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
×
Page 48
Page 49
Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
×
Page 49
Page 50
Suggested Citation:"SESSION 5: Policies and Planning to Minimize the Spread of Disease." National Academies of Sciences, Engineering, and Medicine. 2010. Research on the Transmission of Disease in Airports and on Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/22941.
×
Page 50

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43 SeSSion 5 Policies and Planning to Minimize the Spread of Disease James H. Diaz, Louisiana State University Health Sciences Center Rose M. ong, Cathay Pacific Airways Anthony D. B. evans, International Civil Aviation Organization transmIssIon Patterns of mosquIto-Borne InfectIous dIseases durIng aIr travel: Passengers, Pathogens, and PuBlIc health ImPlIcatIons James H. Diaz (Presenter) in addition to climatic, ecologic, and microbial factors, other significant factors that influence the emergence and reemergence of infectious diseases include international trade and air travel, globalization of agriculture and food production, exotic eating habits, lifestyle, and residential choices. The worldwide spread of the Asian tiger mos- quito, Aedes albopictus, by imported tire shipments on container ships from Southeast Asia has introduced a new secondary (to Aedes aegypti) vector for dengue fever into the tropical Americas and Chikungunya fever in india, Bangladesh, and the indian ocean islands, which are popular travel destination resorts (figure 1). Many models of climate change and vector–patho- gen relationships now predict a significant expansion in potential malaria transmission cycles in the next few decades, with some studies predicting a 16% to 25% increase in person-months of exposure in malaria- endemic areas of Africa. Accessible airline connections now permit infected individuals to travel anywhere in the world in less than 24 h, delivering human reservoirs of malaria, dengue, West nile virus, and Chikungunya fever to new temperate areas for autochthonous or local transmission by new and adaptable mosquito vectors, often recent air or sea arrivals themselves. in 2008, Hochedez and coinvestigators in Paris reported their findings from a prospective study of 62 returning travelers who presented to their tropical dis- eases clinic with fever (above 38°C) and widespread rash over a 20-month period (1). The three main travel des- tinations were the indian ocean islands (35%), Africa (21%), and Asia (18%). The three main tropical infec- tious disease diagnoses were Chikungunya (35%), dengue (26%), and African tick-bite fever (10%). Travel to the indian ocean islands and South Africa was significantly FIGURE 1 The female Aedes albopictus, or Asian tiger mosquito, has been disseminated in coastal temperate zones worldwide by global trade and has genetically adapted to become a competent vector for dengue fever and Chikungunya viruses. (Source: CDC Public Health Image Library, Image No. 4735.)

44 ReSeARCH on THe TRAnSMiSSion of DiSeASe in AiRPoRTS AnD on AiRCRAfT associated with Chikungunya and ATBf, respectively. The authors concluded that arthropod-borne infectious diseases presenting with fever and rash were not uncom- mon among returning travelers and that travelers return- ing from endemic areas should be rapidly screened for tropical infections, some of which could be fatal, such as dengue and malaria. The mosquito vectors of infectious diseases that may be imported by infected passengers are compared by geographic distribution ranges and infec- tious disease transmission in Table 1. History Repeats Itself: Why Is Dengue Fever a 21st Century Public Health Threat? Yellow fever outbreaks claimed tens of thousands of vic- tims in coastal and inland U.S. seaports and throughout Latin America and the Caribbean until stopped by a live virus vaccine developed in the early 20th century. Den- gue virus, like yellow fever, is a flavivirus but it comes from a larger family of dengue viruses and there is no effective vaccine for it. Dengue fever and, in particular, its complications from subsequent dengue infections with other dengue serotypes, such as dengue hemorrhagic fever (DHf) and dengue shock syndrome, may pose spe- cific public health threats to the United States. Dengue is caused by four genetically related flaviviruses (Den1 to -4); is transmitted by container-breeding, peridomestic Aedes species mosquitoes, preferentially Aedes aegypti; and can cause a spectrum of clinical manifestations rang- ing from asymptomatic initial infections to hemorrhagic fever with shock from microvascular plasma leakage. Although an effective live vaccine is available for yel- low fever (another flavivirus transmitted by Aedes mos- quitoes), a dengue vaccine has proven very difficult to develop for several reasons: (a) the four dengue serotypes dictate a polyvalent vaccine, like the influenza vaccine; (b) a dengue vaccine must provide immunity against all four flaviviral serotypes at once by stimulating effective neutralizing antibodies; (c) the neutralizing antibodies must not cross-react and activate T cells, causing the cytokine reactions characteristic of DHf and DSS; and (d) multiple vaccinations every few years will likely be required to achieve long-lasting immunity against all four serotypes. Dengue viruses are now endemic along the U.S.– Mexico border and have caused dengue fever outbreaks on both sides of the border and an autochthonous case of DHf in Brownsville, Texas, in 2005. Although yel- low fever and dengue viruses historically have been con- fined to the tropics and transmitted by Aedes aegypti, a secondary Aedes vector, the Asian tiger mosquito A. albopictus, has now expanded its range globally in a warming ecosystem and is a competent vector of den- gue viruses (figure 1). The World Health organization (WHo) considers dengue to be one of the world’s most important reemerging infectious diseases, with 50 mil- lion to 100 million cases annually; 0.5 million hospital- izations, often requiring blood product transfusions; and 22,000 deaths annually, mostly in children. even though the first dengue infection may be mild, the second could be lethal, even if it occurs years later. As there are no vac- cines or specific drug treatments for dengue and because local A. aegypti and A. albopictus mosquitoes are capa- ble of transmitting dengue in the United States, dengue poses a significant threat to the United States and a safe quadrivalent vaccine and better mosquito vector control along the U.S.–Mexico border are needed now. TABLE 1 Mosquito Vectors of Infectious Diseases That May Be Imported by Infected Travelers or Vectors on Aircraft or in Airports Mosquito infectious Geographic Causative Classification Genera Diseases Transmitted Distribution Ranges Microbial Agents of Causative Agents Anopheles spp. Malaria Africa, Asia, Central America, Plasmodium falciparum, Protozoan parasites South America P. vivax, P. ovale, P. malariae Anopheles spp. Bancroftian filariasis Southeast Asia Wuchereria bancrofti filarial worms causing Brugian filariasis Southeast Asia Brugia malayi lymphatic filariasis Timorian filariasis Timor, indonesia Brugia timori Anopheles spp. o’nyong nyong fever Africa Alphavirus Togaviruses Aedes spp. Yellow fever Africa, Latin America flavivirus flaviviruses Dengue fever Africa, Asia, Latin America flaviviruses Den 1-4 flaviviruses Chikungunya fever Africa, Asia Alphavirus Togaviruses eastern equine eastern & Southeastern USA Alphavirus Togaviruses encephalitis Ross River fever Australia, Papua new Guinea Alphavirus Togaviruses California encephalitis Western USA Bunyavirus Bunyaviruses LaCrosse encephalitis Midwestern USA Bunyavirus Bunyaviruses Rift Valley fever Africa Phlebovirus Bunyaviruses

45PoLiCieS AnD PLAnninG To MiniMiZe THe SPReAD of DiSeASe Why We Could Not Stop the Spread of West Nile Virus Across the United States Although dengue viruses are carried by mosquitoes or infected humans across the porous U.S.–Mexico bor- der, West nile virus was most likely imported to the United States in 1999 by international air travel. The West nile virus arrived in new York City courtesy of an infected passenger or an infected Culex mosquito from an endemic region of east Africa or the Middle east. By 2002, competent local Culex vectors had initially estab- lished a mobile reservoir for West nile virus in wild birds in wet, warming ecosystems that began to fly the virus rapidly across the United States from new York to the west coast. The initial wild animal reservoir for intro- duced West nile virus in the United States was so specific that it targeted mostly birds of the family Corvidae, espe- cially crows and jays. By 2005, West nile virus infec- tions were reported in other wild and domestic animals and humans across the continental United States and had caused more than 4,000 cases of meningoencephalitis with 263 deaths [case fatality rate (CfR) = 6.6%]. Why Are Mosquitoes Such Competent Transmission Vectors of Infectious Diseases in an Era of Climatic Change? only female mosquitoes seek frequent blood meals for their developing eggs from preferred nearby hosts. All female mosquitoes lay their eggs in standing water, either on or just below the surface. The anopheline vectors of malaria prefer to lay eggs in drainage ditches, marshy areas, and puddles. The culicine vectors of West nile virus, dengue, and Chikungunya fever prefer to lay their eggs in containers that trap freshwater, such as flower pots, uncovered garbage cans, and even discarded tires. Climate changes, particularly warming nighttime tem- peratures and increased precipitation, offer selective advantages to all mosquito species, including (a) a longer reproductive life and a prolonged breeding season, (b) opportunities for more blood meals during gestation, (c) plenty of standing water surfaces for egg laying, and (d) a faster egg hatch over days and not weeks. International Air Travel and Malaria Malaria, a mosquito-transmitted parasitic disease, remains the most common cause of infectious disease deaths worldwide, followed by tuberculosis and AiDS. Although there are four Plasmodium protozoans capable of causing malaria in humans (P. falciparum, P. malar- iae, P. ovale, P. vivax), P. falciparum and relapsing P. vivax are the most common causative agents, with P. falciparum having a significantly higher CfR than P. vivax. According to the WHo’s World Malaria Report (2005), 3.2 billion people live in malaria-endemic regions in 107 countries and territories, and there are between 350 million and 500 million cases worldwide per year, with 840,000 to 1.2 million deaths from malaria annu- ally. Most malaria deaths occur in children under age 5 years, in pregnant women, and in nonimmune indi- viduals, often travelers and expatriates returning to their malaria-endemic homelands to visit friends and relatives. About 60% of all cases of malaria worldwide and more than 80% of deaths from malaria worldwide occur in sub-Saharan Africa. Most malaria deaths worldwide are caused by P. falciparum transmitted by highly competent mosquito vectors, such as Anopheles gambiae in Africa, where transmission occurs year round. The most common reasons for malaria to occur in the industrialized nations of north America and europe where malaria was once endemic are also related to international air travel in a warmer and wetter climate and include airport malaria and, more significantly, imported malaria. Airport malaria is defined as the intercontinental transfer of malaria through the intro- duction of an infective anopheline mosquito vector into a nonendemic disease area with a changing ecosystem that supports the vector–pathogen relationship. The malaria-infected mosquito vector is a new arrival on an international flight from a malaria-endemic region. Airport malaria is transmitted by the bite of an infected tropical anopheline mosquito within the vicinity of an international airport, usually a few miles or even less. on the other hand, imported malaria is defined as the intercontinental transfer of malaria by the movement of a parasitemic person with malaria to a nonendemic disease area with locally competent anopheline vec- tors in a welcoming ecosystem. Climate change has now expanded the geographic distribution of malaria- endemic regions worldwide and extended the length of seasonal malaria transmission cycles in endemic regions, so more arrivals of malaria-carrying mosquitoes and malaria-infected travelers are anticipated. The great- est public health threats that imported malaria-infected mosquitoes and patients with malaria pose to nonma- larious regions include the reintroduction of Plasmo- dium species (especially P. vivax in the United States and europe) into regions with competent anopheline vectors and the reestablishment of local or autochtho- nous malaria by local anopheline vectors. Airport Malaria How often do infected mosquitoes travel by air from tropical disease-endemic nations to capital cities in industrialized nations with disease-supporting warming

46 ReSeARCH on THe TRAnSMiSSion of DiSeASe in AiRPoRTS AnD on AiRCRAfT ecosystems? in 1983, random searches of arriving air- planes at Gatwick Airport in London found that 12 of 67 airplanes from tropical countries contained mosquitoes. After the female mosquito leaves the aircraft, she may survive long enough, especially during temperate peri- ods, to take a blood meal and transmit pathogens, usu- ally in the vicinity of an international airport. After one or more blood meals, female mosquitoes seek a water surface to lay their eggs. As international air travel between malaria-endemic nations and malaria nonendemic nations increased, cases of airport malaria have increased. in 1983, two cases of P. falciparum malaria were diagnosed in persons without histories of travel to malaria-endemic regions living 10 and 15 km from Gatwick Airport. Hot, humid weather in Britain may have facilitated the survival of imported, infected anopheline mosquitoes. During the summer of 1994, six cases of airport malaria were diagnosed in the vicinity of Charles de Gaulle Airport near Paris. four of the patients were airport workers, infected at work, and the others were residents of Villeparisis, a small town about 7.5 km from the airport. To reach Villeparisis, the infected anopheline mosquitoes were thought to have hitched a car ride with airport workers who lived next door to two of the patients. Imported Malaria in addition to airport malaria transmitted by infected mosquito air travelers, many countries throughout the developed world are reporting an increasing number of cases of imported malaria because of the increase in long- distance air travel by infected passengers. Malaria cases imported from Africa to the United Kingdom (U.K.) rose from 803 in 1987 to 1,165 in 1993. By 2006, a total of 1,758 malaria cases were reported in the U.K. from 1990 to 1998, the annual number of imported malaria cases in italy increased by 100% due to the rising rates of immigration and international travel, with immigrants currently accounting for most of the cases. in the United States in 2005, a total of 1,528 cases of imported malaria were diagnosed, an increase of 15% over the prior year. Today, imported malaria is the most common type of malaria in developed nations, with more than 10,000 cases reported annually; imported malaria remains the most common cause of fever in travelers returning from malaria-endemic regions. in a retrospective analysis of 380 imported malaria cases in Verona, italy, over the 5-year period 2000–2004 and 2008, Mascarello and coauthors reported that most cases occurred in adults (337 adults vs. 43 children), in immigrants (n = 181, 48% of adults), in patients return- ing from Africa (n = 359, 94.5%), and in travelers return- ing from visiting friends and relatives in malaria-endemic regions (n = 154, 40.5%) (2). Most cases were caused by single P. falciparum infections (n = 292, 76.8%), with few mixed Plasmodium infections (n = 23, 6%) (2). The authors concluded that malaria in travelers returning to Verona from Africa was not uncommon and targeted certain high-risk travelers, including adult expatriate immigrant travelers visiting friends and relatives, semi- immune children (recent immigrants), and nonimmune children (expatriates or born in italy). in a similar retrospective analysis of 109 travelers with malaria returning to Basel, Switzerland, over the period 1994–2004, Thierfelder and coinvestigators reported that P. falciparum was the most common caus- ative parasite (84%); most infections were acquired in Africa in immigrants visiting friends and relatives (82%); and the mean incubation period was 4 days (range 0.5 to 31 days) (3). After their descriptive analysis, the investi- gators conducted three comparative analyses with two prior studies of malaria in travelers returning to Basel during the periods 1970–1986 and 1987–1992. The results of their comparative analyses included significant increases in the proportions of P. falciparum infections over three study periods (1970–1986, 49%; 1987–1992, 75%; 1994–2004, 88%) and significant increases (P < .001) in hospitalizations for P. falciparum malaria over the three decades studied. The authors concluded that there was a significant trend toward more serious malaria infections with P. falciparum in immigrants returning to Basel after visiting friends and relatives in their malaria- endemic native homelands. in 2008, Rodger and coauthors reported a cluster of six cases of P. falciparum malaria at a British airport among 30 students returning to the United States after spending 2 months in east Africa in 2005 (4). of the six patients, all were young (19 to 22 years of age) and in prior excellent health; five of the six exhibited features of acute cerebral malaria (disorientation, prostration) requiring urgent intensive care and therapy with intrave- nous quinine. The authors commended alert U.K. airport staff for recognizing the seriously ill travelers preparing to board a 9-h second-leg flight to the United States and for rapidly evacuating the patients to the nearest health care facility for intensive care, without which the five cerebral malaria cases would likely have been fatal. Although many developed nations, such as northern europe and the United States, do not have as efficient mosquito vectors for P. falciparum malaria as A. gam- biae in sub-Saharan Africa, many nonendemic nations in southern europe, the Middle east, and Asia do have efficient vectors for P. falciparum, and most have compe- tent vectors for P. vivax, including the United States and europe. The most disturbing recent trends in imported malaria today include the following: (a) an increasing proportion of P. falciparum infections capable of caus- ing cerebral malaria and renal failure with the highest

47PoLiCieS AnD PLAnninG To MiniMiZe THe SPReAD of DiSeASe CfRs; and (b) increasing immigration from malaria- endemic regions to malaria-free regions in developed nations, creating a unique set of high-risk travelers, especially expatriates (semi-immunes) and their children (often nonimmune) returning from visiting friends and relatives in their malaria-endemic native homelands. in summary, imported malaria cases are increasing worldwide because of the ease and relatively low costs of international air travel to malaria-endemic regions worldwide. The world’s malaria-endemic regions now have expanded distribution ranges for malaria trans- mission and longer mosquito vector breeding–feeding seasons due to global warming and increasing drought– monsoon cycles. Autochthonous (Locally Transmitted or Reintroduced) Malaria in the United States, 21 outbreaks of presumed locally transmitted or autochthonous mosquito-borne malaria transmission have been reported since 1950, all caused by P. vivax. Most of these introduced malaria outbreaks (n = 14), occurred in southern California, primarily among migrant Mexican agricultural workers. in 1986, a P. vivax malaria outbreak resulted in 28 cases of the disease, 26 of which were in Mexican migrant work- ers, over a 3-month period. in 1988, another outbreak of locally transmitted P. vivax malaria occurred in San Diego County, California, and involved 30 patients, again mostly migrant farm workers, and represented the largest reported outbreak of autochthonous malaria in the United States since 1952. epidemiologic and micro- biologic investigations of these malaria outbreaks later confirmed secondary spread from infected immigrants to other immigrants and local residents transmitted by local malaria-competent anopheline vectors. Conclusions Competent mosquito vectors for dengue, yellow fever, and Chikungunya virus are now present in the United States, including A. aegypti in the southern United States and A. albopictus throughout the country, and are await- ing an opportunity to transmit these imported arboviral diseases locally from arriving infected airline travelers to nonimmune citizens nearby. in addition, anopheline species have demonstrated their capacity to transmit imported P. vivax malaria along the U.S.–Mexico bor- der and to transmit more serious P. falciparum malaria from arriving infected airline travelers and nonimmune individuals in southern europe. Prevention and control strategies for the imported arboviral infectious diseases (Chikungunya virus, den- gue, and West nile virus) and for airport, imported, and autochthonous malaria should include early case defi- nition, case confirmation, and treatment; strengthened vector surveillance to detect the potential for autoch- thonous or local transmission; and drainage of potential mosquito breeding and egg-laying surface water sites. Although the relationships among infected vector impor- tation, index case immigration, reclaimed disease eco- systems, and malaria transmission are complex, future attempts to control and eradicate airport and imported malaria should be based on an understanding of disease transmission mechanisms and an appreciation that cli- mate and ecosystem changes can support reemerging local mosquito-borne infectious diseases in nonendemic areas, especially malaria, dengue, Chikungunya, and West nile virus. References Hochedez, P., A. Canestri, A. Guihot, S. Brichler, f. Bri-1. caire, and e. Caumes. Management of Travelers with fever and exanthema, notably Dengue and Chikungu- nya infections. American Journal of Tropical Medicine and Hygiene, Vol. 78, 2008, pp. 710–713. Mascarello, M., B. Allegranzi, A. Angheben, M. Anselmi, 2. e. Concia, S. Laganà, L. Manzoli, G. Monteiro, and Z. Bisoffi. imported Malaria in Adults and Children: epide- miological and Clinical Characteristics of 380 Consecu- tive Cases observed in Verona, italy. Journal of Travel Medicine, Vol. 15, 2008, pp. 226–236. Thierfelder, C., C. Schill, C. Hatz, and R. nüesch. Trends 3. in imported Malaria to Basel, Switzerland. Journal of Travel Medicine, Vol. 15, 2008, pp. 432–436. Rodger, A. J., G. S. Cooke, R. ord, C. J. Sutherand, and 4. G. Pasvol. Cluster of falciparum Malaria Cases in UK Airport. Emerging Infectious Diseases, Vol. 8, 2008, pp. 1284–1286. Additional Resources Anyamba, A., J. P. Chretien, J. Small, C. J. Tucker, and K. J. Linthicum. Developing Global Climate Anomalies Sug- gest Potential Disease Risks for 2006–2007. International Journal of Health Geographics, Vol. 5, 2006, pp. 60–63. Charrel, R., x. de Lamballerie, and D. Raoult. Chikungunya outbreaks—The Globalization of Vectorborne Diseases. New England Journal of Medicine, Vol. 356, 2007, pp. 769–771. deLamballerie, x., e. Leroy, R. n. Charrel, K. Tsetsarkin, S. Higgs, and e. A. Gould. Chikungunya Virus Adapts to Tiger Mosquito Via evolutionary Convergence: A Sign of Things to Come? Journal of Virology, Vol. 5, 2008, p. 33.

48 ReSeARCH on THe TRAnSMiSSion of DiSeASe in AiRPoRTS AnD on AiRCRAfT Dengue Hemorrhagic fever—US–Mexico Border, 2005. Mor- bidity and Mortality Weekly Report, Vol. 56, 2007, pp. 785–789. Giacomini, T., J. Mouchet, P. Mathieu, and J. C. Petithory. Study of 6 Cases of Malaria Acquired near Roissy-Charles- de-Gaulle in 1994. Bulletin de l’Académie Nationale de Médecine, Vol. 179, 1995, pp. 335–351. Malaria. in International Travel and Health. World Health organization, Geneva, Switzerland, 2005, pp. 132–151. Monath, T. P. Dengue and Yellow fever—Challenges for the Development and Use of Vaccines. New England Journal of Medicine, Vol. 357, 2007, pp. 2222–2225. Morens, D., and A. S. fauci. Dengue and Hemorrhagic fever: A Potential Threat to Public Health in the United States. Journal of the American Medical Association, Vol. 299, 2008, pp. 214–216. Panning, M., K. Grywna, e. P. von esbroek, and C. Drosten. Chikungunya fever in Travelers Returning to europe from the indian ocean Region, 2006. Emerging Infectious Diseases, Vol. 14, 2008, pp. 416–22. Romi, R., G. Sabatinelli, and G. Majori. Malaria epidemiolog- ical Situation in italy and evaluation of Malaria incidence in italian Travelers. Journal of Travel Medicine, Vol. 8, 2001, pp. 6–11. Smith, D. M., C. Cusack, A. W. Coleman, C. K. folland, G. R. Harris, and J. M. Murphy. improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model. Science, Vol. 317, 2007, pp. 766–769. Transmission of Plasmodium vivax Malaria—San Diego, County, California, 1988 and 1989. Morbidity and Mor- tality Weekly Report, Vol. 39, 1989, pp. 91–94. Voelker, R. effects of West nile Virus May Persist. Journal of the American Medical Association, Vol. 299, 2008, pp. 2135–2136. Whitfield, D., C. f. Curtis, G. B. White, G. A. Targett, D. C. Warhurst, and D. J. Bradley. Two Cases of falciparum Malaria Acquired in Britain. British Medical Journal, Vol. 289, 1984, pp. 1607–1609. World Malaria Report. World Health organization, Geneva, Switzerland, 2005. www.cdc.gov/Malaria/impact/index. htm. Accessed feb. 7, 2009. aIrlIne PolIcIes and Procedures to mInImIze the sPread of dIseases Rose M. Ong (Presenter) faced with the outbreak of severe acute respiratory syn- drome (SARS) in 2003, airlines found that they were generally ill prepared to deal with infectious diseases with public health concerns. Since that time, especially for an Asian-based carrier such as Cathay Pacific, there have been a number of other “novel” communicable dis- eases, including avian influenza and most recently the pandemic A/H1n1 influenza epidemic. Air travel is fre- quently cited as being responsible for the rapid spread of communicable diseases on a worldwide basis. Since 2003, significant progress has been made among various commercial airline stakeholders to collaborate to minimize the spread of communicable diseases onboard flights. Airlines followed guidance issued by major inter- national organizations such as the international Civil Aviation organization (iCAo), WHo, U.S. Centers for Disease Control and Prevention, international Air Transport Association (iATA), and Airport Council international (ACi) as well as local organizations such as the Hong Kong Centre for Health Protection. Many initiatives have been introduced by these organizations to promote better alignment and collaboration among key stakeholders in managing infectious diseases in air travel. Airlines engage in routine baseline activities to manage infectious diseases, which include educating and training frontline staff, crew fitness to fly, cabin air conditioning and ventilation, cabin hygiene and sanitation, in-flight catering hygiene, and preparedness drills conducted in conjunction with airport authorities. emphasis was placed on the aircraft ventilation system; it introduces fresh air at a rate of 50%, which is mixed with recircu- lated air and filtered through high-efficiency particulate air filters, with a 99.9% efficiency rate of removal of air- borne biological contaminants. The entire cabin air vol- ume is exchanged every 2 to 3 min with laminar airflow patterns, which minimizes longitudinal air movement, lowering the risk of in-flight transmissions in a forward- and-aft direction. The aircraft is cleaned and disinfected in accordance with maintenance schedules. other actions are taken in response to specific infec- tious incidents, including activation of the in-flight medical management systems (e.g., cabin crew training, in-flight aeromedical telephonic support, medical equip- ment including personal protective equipment, blood- borne pathogen barriers) and contact tracing of crew and passengers as appropriate. Crew have specific pro- tocols to follow when a passenger is suspected of having a communicable disease; the individual is given a mask to wear, relocated to the rear of the aircraft if appro- priate and possible, assigned a toilet if appropriate, and given tissues or a disposal bag to use. one crew mem- ber should be assigned to look after the sick passenger. The crew will communicate with the telephonic medical advisory and, if appropriate and indicated, the pilot will notify the en route air traffic control, who will advise health authorities in the arrival port. During an infectious disease outbreak, additional measures are taken, including screening temperatures of all crew before operating an aircraft, providing refresher training and safety reminders for all crew at crew depar-

49PoLiCieS AnD PLAnninG To MiniMiZe THe SPReAD of DiSeASe ture lounges, stepped-up cleaning of aircraft cabin and equipment, and judicious use of masks by crew. We also developed a series of business continuity plans taking into account the need to balance a positive cash flow position, protecting company brand and reputation while protecting the health and safety of passengers and employees. the PractIcal aPPlIcatIon of World health organIzatIon travel recommendatIons: some oBservatIons Anthony D. B. Evans (Presenter) on April 25, 2009, the WHo emergency Committee [established in accordance with international Health Regulations (iHR-2005)] provided its view to Margaret Chan, Director General of WHo, that an influenza A/ H1n1 outbreak represented a “public health emergency of international concern.” on April 27, 2009, after the second meeting of the emergency committee, Chan raised the level of influenza pandemic alert from Phase 3 to Phase 4. At that time some additional announcements were made, including the following: • Given the widespread presence of the virus, the director general considered that containing the outbreak was not feasible. The focus should be on mitigation mea- sures. • The director general recommended not closing borders and not restricting international travel. This paper discusses the practical application of these recommendations by WHo (www.who.int/en/). International Civil Aviation Organization iCAo is a United nations specialized agency that works to achieve a safe, secure, and sustainable development of civil aviation through cooperation among its mem- ber states (www.icao.int/). its work is underpinned by the Convention on international Civil Aviation (signed in Chicago, illinois, it is also known as the Chicago Convention) of which Article 14 states, in part “each contracting State agrees to take effective measures to prevent the spread by means of air navigation of chol- era, typhus (epidemic), smallpox, yellow fever, plague, and such other communicable diseases as the contracting States shall from time to time decide to designate, and to that end contracting States will keep in close consulta- tion with the agencies concerned with the international regulations relating to sanitary measures applicable to aircraft.” Although written in 1944, upon establishment of iCAo, it remains relevant. it is because of this article that iCAo and the national regulatory authorities for aviation in each contracting state to the Chicago Con- vention undertake work on pandemic preparedness plan- ning, in cooperation with WHo, iATA (www.iata.org/ index.htm), ACi (www.airports.org/cda/aci_common/ display/main/aci_content07.jsp?zn=aci&cp=1_665_2_), and other stakeholders. Airport Screening Although airport screening was not specifically men- tioned in the announcement by Chan at the start of the outbreak, a document posted by WHo on May 1, 2009, entitled “no rationale for travel restrictions” clarified WHo’s view by stating “furthermore, although iden- tifying the signs and symptoms of influenza in travelers can be an effective monitoring technique, it is not effec- tive in reducing the spread of influenza as the virus can be transmitted from person to person before the onset of symptoms. Scientific research based on mathematical modeling indicates that restricting travel will be of lim- ited or no benefit in stopping the spread of disease. His- torical records of previous influenza pandemics, as well as experience with SARS, have validated this point.” Despite this advice from WHo, many states (coun- tries) undertook, and continue to undertake, some form of screening at airports, including the use of thermal imaging to detect individuals with an elevated tempera- ture. in addition, a few states quarantined travelers per- ceived to be at increased risk of incubating influenza. At the other end of the spectrum, some states have taken no action to identify possible cases. This inconsistency of approach has two main disad- vantages: travelers receive mixed messages from authori- tative bodies, resulting in confusion about the actual risk, and those states undertaking screening use resources that might be more effectively used for some other purpose. The cost of screening is not trivial; for example, a thermal scanner may cost tens of thousands of dollars in addition to the cost of training personnel and operating the equip- ment. Medical staffs are required to assess further those individuals identified as having an elevated temperature. As there appears to be little scientific justification for screening passengers at airports, it may be worthwhile exploring further the reasons why states apply such measures. There is some evidence that governments may wish to demonstrate to their citizens that action is being taken to reduce the risk of illness, or they may wish to reassure travelers or deter unwell individuals from fly- ing. A survey of public health authorities could help to elucidate the reasons and form the basis for a more con- sistent approach.

50 ReSeARCH on THe TRAnSMiSSion of DiSeASe in AiRPoRTS AnD on AiRCRAfT Significant Interference with International Traffic one aim of the WHo iHR-2005 is to provide a public health response to the international spread of disease, which avoids unnecessary interference with international traffic and trade. An important description in the iHR is therefore that of “significant interference.” it is found in Article 43, where it is described as “refusal of entry or departure of international travelers, baggage, cargo, con- tainers, conveyances, goods and the like, or their delay for more than 24 hours.” in the aviation sector, delaying an aircraft’s departure by more than a few minutes can disrupt operations and may be regarded as “significant interference” as far as an airline or its passengers and crew are concerned, even though it may not fall into the category of such interference according to the iHR. While aircraft delays for public health reasons may be justified, and unavoidable in certain circumstances, such delays can sometimes be imposed by a public health authority without full knowledge of the effects of such disruption on aircraft operations. one reason for this situation is that much of the work of public health authorities is devoted to issues of national importance, and they may not be so focused on the international implications of their actions. on the other hand, an airline operating in 20 international air- ports may have to comply with many different public health requirements for documentation, screening, and reporting, all of which can cause inefficiencies and delay because they are not standardized. Airlines are therefore well aware of the potentially adverse effects of a lack of international public health harmonization. There may be good reasons for different public health responses from different states, but it appears that such differences often arise because of a lack of coordination between states rather than because of a difference in risk. To minimize such differences, iCAo and WHo are working with the trade associations iATA and ACi as well as other organizations to try to improve harmoniza- tion of the public health response to diseases with pan- demic potential. WHO’s Public Health Mandate According to iHR-2005, its purpose and scope are “to prevent, protect against, control and provide a public health response to the international spread of disease in ways that are commensurate with and restricted to public health risks.” WHo is therefore concerned with health risks that are relevant to the public health—that is, the health of communities. However, other health care providers may approach the question of risk from a dif- ferent viewpoint. occupational health physicians need to take account of the risks to the assets of their company or organization when advising about travel during an outbreak or pandemic. They need to consider risks to efficiency that are unrelated to public health risks, such as the chance that an employee may be stranded abroad (e.g., because of quarantine requirements or because of illness). further, employees may prefer to delay or avoid travel in view of the perceived risk or because they do not wish to be away from home if illness affects their family when they are traveling. in the same manner, a physician advising an individ- ual patient about travel during an outbreak or pandemic may need to take account of specific circumstances that affect only that individual and that do not apply to the community as a whole. The WHo message that travel restrictions and screen- ing are not recommended is reassuring. However, when the other aspects are considered by health care provid- ers, who have a different priority from that of public health, different messages about risk to individuals can contribute to the lack of a clear understanding about the risks involved. Summary iHR-2005 provide a solid basis for implementing pro- portionate measures that mitigate the risk to public health from influenza A (H1n1) by international travel. They permit flexibility to deal with the specific situa- tion that has enabled WHo to provide consistent travel recommendations during the outbreak and subsequent pandemic of influenza A (H1n1). However, such rec- ommendations have not been applied in a harmonized manner. Continued international communication and collaboration among public health authorities and between the public health and aviation sectors should help develop a more harmonized approach. Two Recommendations for Further Research 1. examine the motives of states in implementing screening and evaluate the outcomes of such screening. 2. Assess the effects of screening on the efficiency of aircraft and airport operations.

Next: SESSION 6: Discussion of Topics for Future Research »
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TRB Conference Proceedings 47: Research on the Transmission of Disease in Airports and on Aircraft is the summary of a September 2009 symposium. The symposium examined the status of research on or related to the transmission of disease on aircraft and in airports, and the potential application of research results to the development of protocols and standards for managing communicable disease incidents in an aviation setting. The symposium also explored areas where additional research may be needed.

An article on this report was included in the January-February issue of TR News.

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