Epidemiological, clinical and viral characteristics of fatal cases of human avian influenza A (H7N9) virus in Zhejiang Province, China

Abstract

Background: The high mortality of avian influenza H7N9 in humans is a cause of great concern in China.

Methods: We compared epidemiological, clinical and viral features of H7N9 influenza of 10 fatal cases and 30 survivors.

Results: Increasing age (p = 0.021), smoking (p = 0.04), underlying medical background (p = 0.05) and chronic drug use (p = 0.042) had a strong relationship with death due to H7N9 infection. Serological inflammatory markers were higher in fatal cases compared to survivors. Acute respiratory distress syndrome (100%), respiratory failure (100%), co-infection with bacteria (60%), shock (50%) and congestive heart failure (50%) were the most common complications observed in fatal cases. The median time from onset of symptoms to antiviral therapy was 4.6 and 7.4 days in those who survived and those who died, respectively (p = 0.04). Viral HA, NA and MP nucleotide sequences of isolates from both study groups exhibited high molecular genetic homology.

Conclusions: Age along with a history of smoking, chronic lung disease, immuno-suppressive disorders, chronic drug use and delayed Oseltamivir treatment are risk factors which might contribute to fatal outcome in human H7N9 infection.

Keywords: Avian influenza A (H7N9) virus; Clinical symptoms; Epidemiology; Fatal outcome.