Thu, Feb 16, 2017 - Page 8 News List

Learning from past for flu response

By Lai Shiow-suey 賴秀穗

Taiwan’s first case of H5N6 avian influenza virus was confirmed on Tuesday last week following tests on a dead gosling in Hualien County. Genetic analysis on the virus revealed it to be similar to a 2014 case of H5N6 infection in China’s Sichuan Province, which resulted in human fatalities.

Between May 2014 and the beginning of this year, there have been 16 reported cases of human H5N6 infection spread across several provinces in southern China, 11 of which resulted in fatalities. However, Chinese authorities have yet to confirm the total number of fatalities during this period.

By the end of last year, H5N6 virus epidemics had occurred in Japan and South Korea.

In South Korea, more than 3,000 birds were culled by authorities, while in Japan more than 3 million birds were culled.

However, to date, there have been no reports of human infections in either country, and a single case of an infected cat in South Korea.

H5N6 is a relatively complex virus, forming from four separate strains of the avian influenza virus. According to analysis from China, the virus initially recombined from two strains found in ducks — H5N1 and H6N6, and then combined with two strains found in chickens — H5N2 and H9N2.

For this reason, H5N6 can infect ducks, geese and chickens, as well as humans and other mammals, such as cats.

Although the infection rate of H5N6 in humans is low, once infected, the fatality rate is high.

Epidemiology shows that once one dead bird is found in a flock, it is highly unlikely that only one will have been infected with the virus.

To limit the spread of this highly contagious virus, health officials must quickly investigate the origin of the dead bird, ascertain whether bird populations at nearby poultry farms are also infected and examine the health of staff working at those locations.

In the past few years, three strains of avian influenza capable of infecting humans — H5N1, H7N9 and H5N6 — have originated in China. The strains all came about following the recombination of viral genomes. This poses a serious threat to human health.

In 1996, the H5N1 virus was isolated in the body of a goose in southern China. The H5N1 strain, which was also formed through the recombination of viral genomes, is highly infectious to both birds and humans.

The following year, 18 people in Hong Kong were infected by the H5N1 virus, six of whom died. The outbreak also led to a complete cull of all chickens in the territory.

Then, in 2003 and 2004, the H5N1 virus spread to eight countries in Asia, which led to more than 600 human infections and about 400 fatalities. An unquantifiable number of birds were infected and slaughtered due to the virus.

At present there are 15 nations worldwide affected by avian influenza virus. In Asia — and in particular in China — the avian influenza virus continues to flare up and cause havoc.

The H7N9 strain of the virus originated in China’s Jiangsu Province and formed from the recombination of the H7N1, H11N9 and H9N2 strains.

The first case of H7N9 causing a human fatality was in Shanghai in 2013. Afterward, a succession of fatalities occurred within less than one month, as the epidemic spread north to Beijing and south to Guangdong and Fujian provinces, causing thousands of human infections and more than 100 human fatalities. The human fatality rate was approximately 20 percent.

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