Strains of influenza seen early tend to dominate throughout the season
Early circulation of one influenza strain is typically associated with a reduced total incidence or interference of other strains throughout the season, according to data published online this week.
Edward Goldstein, MD, and colleagues from Harvard School of Public Health looked at data collected by the CDC from 1997 to 2009. The researchers used this data to derive an estimate of the number of new influenza cases per week in the US population and a “cumulative incidence proxy (CIP) for each influenza season,” and then developed a statistical algorithm that accurately predicted the whole-season CIP for a particular strain.
The researchers reported that “all strains exhibited a negative association between their CIP for the whole season (from calendar week 40 of each year to calendar week 20 of the next year) and the CIP of the other two strains (the complementary CIP) from the start of the season up to calendar week 2 (or 3, 4 or 5) of the next year.”
The study researchers also wrote that “for the largest seasons in the data, which were dominated by A/H3N2, prediction of A/H3N2 incidence always occurred at least several weeks in advance of the peak.”
Goldstein and colleagues concluded that it is likely that routine early-season surveillance data could be used to predict the relative size of the epidemics caused by each influenza strain in the United States and in other countries where sufficient surveillance data are available.
Disclosures: The work was supported in part by the US National Institutes of Health Models of Infectious Disease Agent Study program. One of the study researchers, Marc Lipsitch, disclosed consulting income from the Avian/Pandemic Flu Registry (Outcome Sciences, funded in part by Roche) and from Pfizer/Wyeth and from Novartis Vaccines and Diagnostics. The other researchers reported no relevant financial disclosures.
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