NOVEL INFECTIOUS DISEASES: Will H5N6 Cause the Next Pandemic?

Influenza A(H5N6) is an emerging novel avian influenza that apparently derived from a reassortment of A(H5N1) with A(H6N6). H5N6 was first reported in domestic poultry in early 2014 from Laos, Vietnam, and China. Since then it has continued to be widely reported from domestic flocks in these countries (primarily China).

In April 2014, the first case of a human infected with the H5N6 influenza virus was reported from Sichuan Province in China. Since then, seven additional human cases have been reported, all from China. The most recent case was reported from Jieyang, Guangdong Province a few days ago. Of these eight cases, six have been reported by the World Health Organization (see links below).

Based on onset dates two of these cases occurred in 2014, four in 2015. Onset dates for the two most recent cases have not yet been reported. Among these cases are five males and three females. One of the females was pregnant. Her child was delivered by caesarian section and the woman is apparently still under treatment. Media reports indicate that the child was not infected. Ages range from 25 to 50 years old. Five the eight have died according to media reports.

Discussion

To date, there is no evidence of human-to-human transmission among these eight cases of H5N6. The fatality rate is high, but there are too few cases to project a fatality rate for a larger population of infected individuals. It is not known if subclinical cases of H5N6 are occurring. No asymptomatic cases have been reported and there are no reports of seroprevelance studies of H5N6 among humans.

As shown in the map below, these eight cases from the past two years are widely scattered over China. The map also depicts the location of reported H5N6 outbreaks in poultry flocks in southern China and northern Laos. Like the distribution of human cases, domestic flocks infected with H5N6 are widely scattered across a large area. The wide-spread geographic distribution of infected poultry along with the dispersed nature of human infections in this area suggests that more human cases are likely to be reported in the future. With such a large animal reservoir this influenza virus could reassort and become more easily transmitted to humans. Were H5N6 to pick up the ability to transit easily among humans, H5N6 could become a deadly pandemic virus.