Incidence of asymptomatic human influenza A(H5N1) virus infection

When virologists Fouchier and Kawaoka were isolating avian influenza H5N1 viruses that could transmit among ferrets by aerosol, there was consternation from some quarters that such viruses might escape from the laboratory and cause a pandemic in humans. Part of the fear came from the fact that the case fatality ratio for human infections with the H5N1 virus exceeds 50%. This number could be substantially higher than the lethality ratio, which is the number of symptomatic cases divided by the total number of infections. Divining the latter number has been difficult. Results of a meta-analysis published in 2012 suggest that H5N1 seropositivity approaches 1-2% in certain populations. Others have concluded that these studies are flawed, clouded by false positives and cross-reacting antigens. Recently two additional studies have been published that contribute to this discussion. The first paper is a case report of subclinical avian influenza H5N1 virus infection in a Vietnamese household in which family members were involved in slaughtering, preparing, and consuming chickens, and birds were permitted to roam freely in the sleeping area. Four chickens from this household were found to be positive for H5N1 virus by polymerase chain reaction (PCR) of throat and cloacal swab specimens. The 40-year old father died after a severe two day respiratory illness requiring hospitalization; H5N1 viral RNA was detected by PCR of a throat swab on day 3 of illness. A throat swab from his daughte...
Source: virology blog - Category: Virology Authors: Tags: Basic virology Information asymptomatic avian Bangladesh case fatality ratio fouchier influenza A(H5N1) kawaoka mortality ratio viral virus Source Type: blogs