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Real-time sero-surveillance may be useful in mitigating emerging influenza pandemics
Wu JT. PLoS Med. 2011;doi:10.1371/journal.pmed.1001103.
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The collection of 150 specimens per week when community transmission of pandemic influenza was confirmed may have yielded reliable hospitalization information in children and adolescents, according to study results.
Researchers in Hong Kong used viral microneutralization to test 14,766 serum samples that had been collected during the first wave of the 2009 H1N1 influenza A pandemic in Hong Kong. Estimates of the infection attack rate and infection-hospitalization probability were made from serial cross-sectional serologic data and hospitalization data available.
Had serologic data been available in real time, hospitalization estimates would have been made 1 week after, 1 to 2 weeks before and 3 weeks after peaks in the epidemic for the following age groups: those aged 5 to 14 years, 15 to 29 years and 30 to 59 years, respectively. The ratio of infection attack rate decreased with age and was a major determining factor in obtaining reliable timely estimates.
If sero-surveillance had begun 3 weeks after confirmation of community transmission, the collection of 150 specimens per week in the 5- to 14-year-old age group, 350 specimens per week in the 15- to 19-year-old group and 500 specimens per week in the 20- to 29-year-old group would have yielded reliable infection-hospitalization estimates for these age groups 4 weeks before the peak, according to the results. The collection of 800 specimens per week in the 30- to 59-year-old age group would not have generated reliable estimates until the peak because the ratio of infection attack rate to pre-existing seroprevalence in this age group was low.
Test specificity should be near 100% or pre-existing seroprevalence should be near zero for the performance of serial cross-sectional sero-surveillance to be most effective, according to the researchers. However, choosing a higher titer cutoff for seropositive could mitigate these potential limitations. Sero-surveillance with 300 specimens per week may result in reliable estimates when the attack rate reaches 6% to 10% if the time for epidemic doubling is more than 6 days.
“Serial cross-sectional serologic data together with clinical surveillance data can allow reliable real-time estimates of [infection attack rate] and severity in an emerging pandemic,” the researchers wrote. “Sero-surveillance for pandemics should be considered.”
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