Urbanization and Slums Infectious Diseases in the Built Environment: Proceedings of a Workshop (2018) / Chapter Skim
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4 Translating Conceptual Models of Infectious Disease Transmission and Control into Practice
4 Translating Conceptual Models of Infectious Disease Transmission and Control into Practice
Pages 35-60
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From page 35... ...
EFFECT OF THE WEST AFRICA EBOLA VIRUS DISEASE OUTBREAK ON OTHER INFECTIOUS DISEASES Frank Mahoney, senior immunization officer at the International Federation of Red Cross and Red Crescent Societies, spoke about the effect of the West Africa EVD outbreak on the epidemiology of other infectious diseases based on his experience as a medical epidemiologist with the U.S.
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From page 36... ...
At the time, he said, many health care workers in the area were not trained to scrupulously reduce exposure to infectious bodily fluids. Effect of the Outbreak on the Health Workforce and Health Services Provision According to Mahoney, the EVD outbreak in West Africa had a substantial effect on the health systems in the region between 2014 and 2015, affecting both the health workforce and the provision of health services in the region.
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From page 37... ...
Mahoney reported that there was a subsequent decrease in the use of health care services during the outbreak, which has been documented by multiple studies on the effect of the EVD outbreak on health care delivery in West Africa. For example, he cited a study that investigated the average monthly consultations for children under 5 years of age before and during the EVD outbreak in Sierra Leone, finding reductions in visits for malaria (–27 percent)
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From page 38... ...
He described a study that modeled the effect of the EVD outbreak on the malaria, HIV, and TB disease burdens in Guinea, Liberia, and Sierra Leone. He said that the analysis attributed approximately 7,000 additional deaths from malaria as a result of the outbreak and a change of approximately 50 percent in malaria-attributable mortality rates in all three countries.1 For HIV, he said, they estimated around 1,000 additional deaths and a change in the HIV-attributable mortality rate of around 15 percent.2 He added that for TB they estimated around 3,000 additional deaths and a subsequent 50 to 60 percent change in the TB-attributable mortality rate (Parpia et al., 2016)
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From page 39... ...
. Mahoney reiterated that the EVD outbreak had major effects on the health workforce and on health service delivery in the region, which led to decreases in access and use of services for major infectious diseases.
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From page 40... ...
; safe transportation; prevention of transmission in the health care setting; and safe burials. He noted that the strategy did not include treatment within the existing health care system, distribution of home health care kits, wide-scale support for water and distribution of hygiene kits, or the involuntary quarantine of infected households.
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From page 41... ...
That said, she noted that achieving sustainability of access and safety of drinking water remains a struggle -- not only in how to go about it but how to measure it. For the purposes of the MDGs, she noted, sustainable access to safe water was defined as the proportion of the population using improved drinking water sources.
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From page 42... ...
Despite its wet climate, Gurley noted, it is difficult to access safe drinking water in Arichpur. She noted that Bangladesh has done much work to improve access to drinking water: cities have improved their water sources and the majority of the country's residents have access to improved water sources, mostly from municipal water supplies (57 percent)
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From page 43... ...
In a survey study, she said, they enrolled 50 of the 120 drug sellers identified in Arichpur and asked them to send the researchers a daily text message with the number of ORS packets sold at the end of the day. She explained that the ORS sales data were compared to the traditional cholera surveillance system that was already in place in Dhaka.
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From page 44... ...
. For every confirmed case, she explained, they enrolled sets of spatially matched control households and then compared households distributed throughout these communities, looking for spatial clustering of high-risk factors for waterborne disease in general and cholera in particular.
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EMERGING VECTOR-BORNE AND ZOONOTIC DISEASES IN BRAZILIAN SLUMS Albert Ko, professor and chair of the Department of Epidemiology of Microbial Diseases at the Yale School of Public Health, discussed emerging vector-borne and zoonotic diseases in Brazilian slum communities. He described some of the challenges related to identifying drivers of transmission in urban slum environments and highlighted the contribution of gradients to disease risk, both between seemingly disparate communities in the urban macroenvironment as well as the slum microenvironment within communities.
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From page 46... ...
46 FIGURE 4-3 Different barriers facilitate or constrain the flow of pathogens from one species to another. NOTES: The width of the gaps between barriers signifies the ease of spillover transmission depending on context.
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From page 47... ...
He added that there is a lack of sound environmental sampling methods, particularly for pathogens, and poor linkage between environmental sampling data and human outcomes. He noted that human exposures are highly stochastic processes in urban slum communities, and that researchers must rely on imprecise proxies.
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From page 48... ...
They also found that even small amounts of rainfall -- not only extreme events -- also contribute to risk, he added, with increases in cases (including a lag time of 1 to 2 weeks that is roughly the incubation period for leptospirosis) indicating that exposures occur during or shortly after rainfall events in urban slum communities.
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From page 49... ...
Potential Influences of the Environment and Social Gradients on Infection Transmission Ko described a study that demonstrates the influence of the environment and social gradients on Leptospira infection. A long-term cohort study in Pau da Lima used tracking boards and surveys to identify risk factors associated with spillover infections or exposures, he said, and analysis found several significant covariates (Reis et al., 2008)
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From page 50... ...
He noted that addressing the issue of social gradient to risk is more complex, but strategies might include a better understanding of the psychosocial factors that place young males at risk for leptospirosis, sexually transmitted infections, violence, and drug use in poor urban slum communities. He described the Fiocruz-Cornell Global Infectious Disease Training Program, a community-driven initiative for social equity and urban leptospirosis prevention that has been under way over the last 20 years in collaboration with the government of Brazil.
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From page 51... ...
TUBERCULOSIS TRANSMISSION IN CAPE TOWN, SOUTH AFRICA Robin Wood, chief executive officer of the Desmond Tutu HIV Centre and Foundation at the University of Cape Town, focused his presentation on the transmission of TB in Cape Town, South Africa, where the country is estimated to have the highest burden of TB in the world. The city of Cape Town alone has more TB case notifications per year (around 26,000)
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From page 52... ...
. Modeling the Risk of Airborne Infectious Disease Using Exhaled Air Wood focused more closely on the component of the modified WellsRiley equation that represents social mixing and the environment.
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. Using Continuous Personal Carbon Dioxide Monitors to Calculate Shared Air Wood explained that carbon dioxide disseminates rapidly, and he and his colleagues believe that carbon dioxide behaves in a similar way to the small particles (1 to 2 microns in size)
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From page 54... ...
To illustrate the conditions of classroom ventilation in modern schools, Wood used a figure adapted from a 2008 study that plotted the correlation between mean indoor carbon dioxide concentrations against airflow rate per person in 62 naturally ventilated classrooms in Europe and North America (Santamouris et al., 2008) (see Figure 4-5)
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From page 55... ...
. Wood concluded by arguing that air volumes exchanged are major drivers of TB, especially in South Africa, and that rebreathing is facilitated by social mixing and environmental conditions.
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From page 56... ...
Wood provided another example of the Pollsmoor Prison in Cape Town, South Africa, where hundreds of people are housed in a single room with no ventilation -- that room in the prison is subject to exactly the same building code as a domestic bedroom in the same area, he said. Wood suggested that TB control programs should be tailored to social circumstances to achieve their aim of decreasing TB prevalence.
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From page 57... ...
He added that the TB control program was ordered to stop the campaign because it was no longer cost-effective according to global guidelines, even though it was effective for the specific context. David Nabarro, advisor for health systems and sustainability at 4SD, suggested that the superspreader issue should be considered in every effort against infectious diseases, be it cholera, influenza, or TB.
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From page 58... ...
He reiterated that the people managing Ebola patients need to be mentored by those with experience and said that Nigeria was fortunate to have experienced people as part of the effort. Mahoney added that Nigeria's Field Epidemiology Training Program did a great job contact tracing, that the Polio Incident Management Team was brought in to help manage the outbreak response, and that the response had a strong infrastructure of
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From page 59... ...
Christopher Braden, deputy director of the National Center for Emerging and Zoonotic Infectious Diseases, CDC, asked if new technologies will enable more sensitive types of environmental sampling. Ko replied that this is a critical research need and technology is improving, but there are several barriers.
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From page 60... ...
She noted that surveillance for cholera is one way to implement that, but there are many other potential ways. Espinal concluded the discussion by remarking that the presentations underscored the importance of the International Health Regulations and the Global Health Security Agenda in ensuring that countries implement essential public health functions to contain outbreaks and emergencies.
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