Systematic review and meta-analyses of cases and deaths associated with highly pathogenic avian influenza H5N1 in humans and poultry

Abstract

From 2003 to date (2015), confirmed highly pathogenic avian influenza (HPAI) H5N1 outbreaks in poultry and humans have been reported, however, certain quantitative parameters remain lacking. We obtained 846 reports of HPAI H5N1 outbreaks in poultry in Africa (2006–2015), and 844 reports in humans globally (2003–2015) from different databases. Data were filtered and analysed using meta-analyses. The outputs were generated for each country included in the study and for overall morbidities, mortalities and case fatalities (for poultry and humans). Approximately 11.6 million poultry were included in the analyses as susceptible with 1.9 million cases and 1.7 million deaths in poultry. In humans, 449 deaths were linked to influenza A H5N1 infections. For all poultry outbreaks in 2006–2015 in Africa, an overall mean apparent morbidity of 48.7% (n = 1 850 589) was estimated, with overall mean apparent mortality being 40.2% (n = 1 705 388) and overall mean case fatality rate (CFR) for HPAI H5N1 outbreaks in poultry being 86.4% (n = 1 705 388). In humans, the overall mean CFR for A H5N1 globally for 2003–2015 was 62.3% (n = 449). Indonesia, Egypt and Vietnam had higher proportions of all human deaths associated with the A H5N1 and Egypt had a significant age–sex bias. Improved reporting and effective quantitation remain key to understanding the characteristics of the virus.