Gray GC, Krueger WS, Chum C, Putnam SD, Wierzba TF, Heil GL, Anderson BD, Yasuda CY, Williams M, Kasper MR, Saphonn V, Blair PJ.
PLoS One. 2014 May 12;9(5):e97097. doi: 10.1371/journal.pone.0097097. eCollection 2014.
In 2008, 800 adults living within rural Kampong Cham Province, Cambodia were enrolled in a 2 year prospective cohort study of zoonotic influenza transmission. Apart from symptomatic human influenza infections a single symptomatic H5N1 infection of avian origin was identified.
Interestingly a handful of symptomatic avian influenza infections were identified using patient sera. Using a conservative WHO accepted cut off for serum titers one individual scored positive using a H9N2 test virus and two others for a H12N5 virus. As the titer of human H5N1 convalescent sera wanes within one year these numbers are probably underestimates.
The paper shows that more strains of avian influenza viruses infect man than judged by symptomatic infections. Spill over resulting in asymptomatic infection could well be relatively common with symptomatic infections being a subset.
