Abstract
BackgroundIn this prospective study we sought to examine seroepidemiological evidence for acute zoonotic influenza virus infection among Romanian agricultural workers.MethodsSera were drawn upon enrollment (2009) and again at 12 and 24 months from 312 adult agriculture workers and 51 age-group matched controls. Participants were contacted monthly for 24 months and queried regarding episodes of acute influenza-like illnesses (ILI). Cohort members meeting ILI criteria permitted respiratory swab collections as well as acute and convalescent serum collection. Serologic assays were performed against 9 avian, 3 swine, and 3 human influenza viruses.ResultsDuring the two-year follow-up, a total of 23 ILI events were reported. Two subjects' specimens were identified as influenza A by rRT-PCR. During the follow-up period, three individuals experienced elevated microneutralization antibody titers ≥1∶80 against three (one each) avian influenza viruses: A/Teal/Hong Kong/w312/97(H6N1), A/Hong Kong/1073/1999(H9N2), or A/Duck/Alberta/60/1976(H12N5). However, none of these participants met the criteria for poultry exposure. A number of subjects demonstrated four-fold increases over time in hemagglutination inhibition (HI) assay titers for at least one of the three swine influenza viruses (SIVs); however, it seems likely that two of these three responses were due to cross-reacting antibody against human influenza. Only elevated antibody titers against A/Swine/Flanders/1/1998(H3N2) lacked evidence for such confounding. In examining risk factors for elevated antibody against this SIV with multiple logistic regression, swine exposure (adjusted OR = 1.8, 95% CI 1.1–2.8) and tobacco use (adjusted OR = 1.8; 95% CI 1.1–2.9) were important predictors.ConclusionsWhile Romania has recently experienced multiple incursions of highly pathogenic avian influenza among domestic poultry, this cohort of Romanian agriculture workers had sparse evidence of avian influenza virus infections. In contrast, there was evidence, especially among the swine exposed participants, of infections with human and one swine H3N2 influenza virus.
Highlights
Since 2003, the World Health Organization has collected data from more than 600 human infections of highly pathogenic avian influenza (HPAI) H5N1 virus occurring in at least 15 countries
Since 45% of Romanians reside in rural areas, populated with small subsidence farms, a large population of Romanians may have experienced exposure to avian influenza viruses (AIVs) that may have spilled over from migrating birds into domestic birds [1]
Viral antigens, and control antisera were obtained from acknowledged collaborators, Biodefense and Emerging Infections (BEI) Research Resources Repository, or through the Influenza Reagent Resource (IRR) program of the US CDC
Summary
Since 2003, the World Health Organization has collected data from more than 600 human infections of highly pathogenic avian influenza (HPAI) H5N1 virus occurring in at least 15 countries. When migrating birds, intermingling in Romania’s Danube Delta introduced HPAI H5N1 into Romanian poultry in 2005, we initiated serology studies to screen Romanian agriculture workers and controls for avian influenza infection [1]. A previous study examined serologic evidence of zoonotic influenza infection upon enrollment and found evidence of previous infections with avian-like A/Hong Kong/1073/1999(H9N2) [1]. This report presents data from 2 years of following the cohort. In this prospective study we sought to examine seroepidemiological evidence for acute zoonotic influenza virus infection among Romanian agricultural workers
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