(Bloomberg) — Genetic variations in the deadly bird flu virus circulating in China increase the potential for a pandemic strain to emerge, researchers in Shanghai said.
Three new variants of the avian influenza type-A H7N9 virus have been found this winter, spurred by transmission in poultry and the incorporation of genetic material from another strain called H9N2, scientists at the Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences said. The new strains may be behind a surge of infections in Guangdong, the southern province bordering Hong Kong.
So far, 178 people are known to have been infected with H7N9 this year, 19 more than in 2013, according to a list of confirmed cases kept by Internet message board FluTrackers. Each case increases the risk of the virus becoming better suited to humans, rather than birds, giving it the ability to spread easily from person to person. Zhejiang and Guangdong provinces and the Shanghai metropolitan area have been the worst affected regions, the scientists wrote in a paper published in Eurosurveillance yesterday.
The rapidly increasing number of cases of A(H7N9) virus infection in these three regions may raise concerns as to whether there is an association between circulation of the new A(H7N9) reassortment strains identified and accelerated transmission of A(H7N9) virus in humans,” the scientists said. “It is of the utmost importance to monitor the risk of a potential pandemic initiated by various influenza virus strains.”
Even though H7N9 hasn’t mutated to become as contagious as seasonal flu, strains that emerge in China are of special interest to researchers. The 1957-58 Asian Flu and 1968-69 Hong Kong Flu pandemics were first identified in the world’s most populous nation, and an earlier bird flu strain known as H5N1 is thought to have come from the southern province of Guangdong in 1996. Years later, a new seasonal flu was found in neighboring Fujian and triggered explosive epidemics worldwide.
H7N9 has infected about 350 people, killing more than 70, mostly in mainland China, according to FluTrackers.
The new reassortments generated by H7N9 and H9N2 strains may produce variants that are more adaptive and have an increased ability to cause disease in humans, according to the Eurosurveillance report.
“Our findings suggest there is a possible risk that a pandemic could develop,” the authors said.
So far, there is no evidence of sustained human-to-human transmission, the World Health Organization (WHO) in Geneva said in a Feb. 11 statement.
“Each new strain could be one that is better genetically equipped to transmit form person to person,” Ian Mackay, an associate professor of clinical virology at the University of Queensland in Brisbane, said in an e-mail today. “Without contemporary sequence analysis, such a strain could emerge from among the ‘noise’ of human infection by less efficient strains, to begin spreading rapidly and with pandemic potential.”
It’s impossible to predict whether such a virus with the ability to spread worldwide would remain so deadly, killing about one in five people known to have been sickened with it.
Yesterday’s research was based on a study of 72 genetic sequences of a flu gene called PB1 analyzed from samples collected in 11 Chinese provinces and cities since March 2013.