Q1: Among the 340 cases of avian influenza (H5N1) virus infection in the world to date, which age group has the highest case fatality rate?
A: The overall case fatality rate is highest among persons 10 to 19 years of age and lowest among persons 50 years of age or older. Whether preexisting immunity, differences in exposure, or other factors might contribute to the apparently lower frequency of infection (90% of patients are 40 years of age or younger) and lethal illness among older adults is uncertain.
Q2: What is the best method for diagnosing avian influenza A (H5N1) virus infection?
A: Detection of viral RNA by means of conventional or real-time reverse-transcriptase polymerase chain reaction remains the best method for the initial diagnosis of influenza A (H5N1). These assays can provide results within 4 to 6 hours and can be performed under biosafety level 2 conditions. Diagnostic yields are higher with throat specimens than with nasal swabs because of higher viral loads of influenza A (H5N1) in the throat. However, nasal swabs are also useful for detecting human influenza viruses, so collection of both specimens is recommended.
Teaching topics from the New England Journal of Medicine - Vol. 358, No. 3, January 17, 2008