Risk Factors Associated with Severe Clinical Outcomes of Pandemic H1N1 Infection

Abstract

The clinical outcome of pandemic H1N1 influenza infection is dependent on the interplay of virus and host factors. Influenza virus infections can range from relatively mild infections of the upper respiratory tract to fatal disease of the lower respiratory tract. A range of host factors play a role in the severity of clinical disease in pdm(H1N1)09 infection. With the exception of neonates age was directly proportional to the severity of clinical outcome; obesity, COPD and pregnancy play a key role in clinical outcome of infection. An important determinant in the pathogenesis of influenza infection is the tissue tropism of the influenza virus. The D222G and D222N mutations of pdm(H1N1)09 influenza appear to have an increased tropism for the tissues of the lower respiratory tract and are disproportionally associated with severe clinical disease. These α2-3 salicylic acid tropic mutations, which have been associated with fatal cases of influenza infection, have also been preferentially selected for during sequential passage in embryonated eggs and viruses of avian origin.