FLU NEWS SCAN: H5N1 in India, avian flu and migration, spring vs fall H1N1 wave, school closure and H1N1

Feb 7, 2012

India confirms 4 H5N1 outbreaks in crows
India today confirmed four recent outbreaks of highly pathogenic H5N1 avian flu that killed more than 1,100 crows, according to a report filed with the World Organization for Animal Health (OIE). The first and by far the largest was in Jharkhand state from last Oct 30 to Dec 12 and involved 1,143 dead crows. The mass crow deaths were reported last year in the media. The report also details two outbreaks that started on Jan 3, each involving five dead crows. One was in Maharashtra state and ended Jan 10; the other was in Orissa state and ended Jan 11. Finally, an outbreak in Bihar state lasted from Jan 10 through Feb 3 and involved six crow fatalities. H5N1 was confirmed in each outbreak at the High Security Animal Disease Laboratory in Bhopal.
Feb 7 OIE report

Study shows summer circulation of low-path avian flu in California
Small populations of waterfowl in California's Central Valley wetlands in the summer and warm conditions do not prevent circulation of low-pathogenic avian influenza (LPAI) in migratory birds, according to a study yesterday in PLoS One. US researchers collected water and fecal samples at 10 wetlands in the Yolo Bypass and Sacramento Valley regions every 2 weeks from late July to late August 2010. During this time, bird populations are relatively small—in the thousands—and high temperatures may mitigate against viral persistence, the team hypothesized. Using reverse transcription polymerase chain reaction, they detected LPAI in 29 of 367 fecal samples (7.9%) and 12 of 597 water samples (2.0%). Of those, the scientists were able to isolate two H3N8, two H2N3, and one H4N8 virus from fecal samples but no live viruses from water samples. They conclude, "Our findings indicate that resident waterfowl populations in southern wetlands may serve as a source of virus for migratory ducks during winter."
Feb 6 PLoS One study

Study: High spring 2009 flu-like incidence did not protect against big fall wave
A high incidence of influenza-like illness (ILI) in the spring 2009 pandemic wave did not appear to lower the risk of a strong ILI peak that fall, a study today indicated. Investigators from Johns Hopkins and the US Centers for Disease Control and Prevention (CDC) studied ILI data from the Outpatient Influenza-like Illness Network, which is a collaboration among the CDC, health departments, and healthcare providers. They evaluated the likelihood of high early-fall ILI incidence given high spring incidence in core-based statistical areas (CBSAs). They wrote, "CBSAs with high spring ILI ratios proved more likely than unaffected CBSAs to have high early autumn ratios, suggesting that elevated spring illness did not protect against early autumn increases."
Feb 7 Epidemiol Infect abstract

Alberta school closures may have helped slow H1N1 spread
Closing schools may help slow disease spread and should be considered during an influenza pandemic, according to a modeling study today in the Annals of Internal Medicine that compared patterns of confirmed pandemic 2009 H1N1 flu (pH1N1) with the school calendar and weather patterns in Alberta. A Canadian team of scientists used age-specific, confirmed cases of pH1N1 from a provincial database of 35,510 specimens gathered from Apr 19, 2009, through Jan 2, 2010. They incorporated those data with information from school calendars and weather patterns, using a "susceptible-infectious-removed" model to estimate the effect of school closings on the spread of pandemic flu. They found that closing schools for the summer resulted in a large drop in transmission. They write, "Although our models cannot include all relevant factors, we have shown that this result is robust to a wide range of assumptions." In a press release, lead author David Earn, PhD, of McMaster University stated, "Our study demonstrates that school-age children were important drivers of pH1N1 transmission in 2009." The model also indicated that seasonal weather changes significantly affected flu transmission in Alberta cities but were much less important than school closures. In listing study limitations, the authors acknowledge that their data "probably represent a small sample of all viral infections."
Feb 7 Ann Intern Med study
Feb 6 McMaster press release

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