Dec 12, 2012
Study finds substantial flu virus shedding even without symptoms
In a German study, 30% of patients' tested positive for flu the day before symptoms developed, and asymptomatic patients had about the same viral loads as sick patients, according to a report yesterday in PLoS One. Investigators conducted a prospective household study using data from 2007 to 2011 in Berlin and Munich. They analyzed data from 122 index patients and 320 household contacts, of whom 67 became secondary flu case-patients. Of the 189 case-patients, 12 had seasonal H1N1 flu, 19 had H3N2, 98 had pandemic 2009 H1N1, and 60 had influenza B. Nine (14%) of 65 unvaccinated secondary case-patients—all adults—were asymptomatic. Viral loads in patients' nasal specimens peaked on day 1, 2, or 3 for all flu strains, then declined steadily till days 7 through 9. On the day before symptom onset, 12 of 40 specimens (30%) were positive. Viral load in six asymptomatic patients was similar to that in those having symptoms. Infectiousness, as measured by viral culture, lasted 4 to 6 days after symptom onset, and viral load did not seem to be influenced by antiviral therapy, age, or vaccination status, the team found. They conclude, "Asymptomatic/subclinical infections occur infrequently, but may be associated with substantial amounts of viral shedding."
Dec 11 PLoS One study
Public health infrastructure key to fighting pandemics, outbreaks: review
A breakdown or absence of public health infrastructure was by far the No. 1 driving factor in recent infectious disease outbreaks of international concern, such as the 2009 H1N1 pandemic and polio, cholera, and yellow fever epidemics, according to a review of nearly 400 outbreaks. A team of US scientists reviewed 197 internationally significant outbreaks from 1996 through 2009 and identified driving factors that contributed to each. They found that a breakdown or absence of public health infrastructure was the driving factor in 39.5% of the outbreaks, and that all other driving factors—such as climate change, urbanization, and international travel and trade—accounted for less than 10% of outbreaks. They conclude: "We suggest a central role for development agencies in pandemic prevention and highlight three critical policy issues." The team suggests that agencies (1) develop policies that deal with different stages of emergence, from spillover and localized outbreaks to pandemic spread, (2) use a systems approach to pandemic prevention that addresses pathogen dynamics at the intersection of people and their environment, and (3) shift funding from short-term emergency funds to a longer-term strategy.
Dec 11 PLoS Med review