The Swine Flu Affair Decision-Making on a Slippery Disease (1978) / Chapter Skim
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Technical Afterword
Technical Afterword
Pages 87-95
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From page 87... ...
The influenza virus can cause this syndrome, although not always exactly the same symptoms, and the severity of the disease ranges from very mild to fatal; death usually comes from rapidly progressive pneumonia.39 Many other infectious agents, mostly viruses, can produce illness resembling that caused by the influenza virus.40 Influenza-the-virus certainly predominates as a cause of influenza-the-disease during epidemic periods, but other viruses are relatively more prominent as producers of year-in and year-out influenza-like illness. Persons who are vaccinated and protected against the influenza virus remain susceptible to "flu" when caused by other organisms.
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From page 88... ...
, computes an "excess mortality" rate per 100,000 population covered, and then extrapolates to the entire population to derive a total number of excess deaths in the country.42 Computation of excess mortality is a sensitive way to identify the occurrence of an epidemic, but it may be an inaccurate indicator of influenza's importance as a national health problem. First, urban centers, having relatively dense concentrations of people, would be more likely to experience epidemic outbreaks; extrapolating from 70 million city dwellers to the entire country may therefore exaggerate national experience.
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From page 89... ...
In addition, for type A viruses, its specific H and N antigens may be cited, usually in parentheses following the strain designation. The swine flu virus, for example, was formally named A/New Jersey/8/76 (Hsw1N1)
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From page 90... ...
One additional phenomenon is worth noting here: the second wave of a particular virus sub-type occasionally causes more deaths than the first wave. This was true of the 1918 pandemic worldwide, of the 1968-70 Hong Kong epidemics in Europe, and possibly of the 1889-90 Asiatic influenza.54 It is not clear whether a particular virus may attain increased infectivity or virulence over time, whether some people become sensitized and overreact to subsequent infection or whether there is some other explanation.
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From page 91... ...
Circumstantial evidence supports the idea that antigenic shifts in human influenza are due to recombinants of animal and human viruses.58 The theory is that a human core gains animal surface antigens. Such a recombinant event, producing an antigenic shift, is believed prerequisite to worldwide pandemic.
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From page 92... ...
Tensions may impend in and among agencies, to say nothing of researchers with different agendas. Naturally acquired influenza stimulates many of the body's defenses against subsequent infection: local defense cells gear up, secretory antibodies coat the respiratory tract and serum antibodies circulate in the blood.
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From page 93... ...
Producing vaccine entails a series of connected steps.73 The first two are isolation of the virus and preparation of recombinant strains. Kilboume pioneered recombinant technique.74 His laboratory still sets standards and has customarily prepared recombinant strains for vaccine production, as with swine flu.
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From page 94... ...
The duration of protection from a shot of influenza vaccine is controversial, but there probably is some decline in protection after about six months.79 Part of the reason for disagreement is that those who believe in longer term protection attribute rising attack rates to antigenic drift in the virus. Different methods for assessing vaccine effectiveness can produce differences in apparent efficacy.
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From page 95... ...
Laboratory identification of the influenza virus would solve that, but isolation of the virus is too inconsistent among cases to be useful in assessing vaccine effectiveness. Clinicians often rely on a four-fold rise in antibody level, from before to after illness, to show infection by a particular agent.
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