Image: USDA Before this year the H7N9 bird flu virus linked to 133 human infections and 43 deaths was never seen in people. All the available evidence suggests that an effective biological barrier apparently kept a pandemic at bay—humans only contracted the novel virus via direct contact with poultry or environments such as live bird markets rather than by human-to-human transmission. New analysis from the Chinese Academy of Agricultural Sciences (CAAS), however, suggests that the virus is closer to becoming a disease transmitted among humans than previously thought. A large study comparing the genomes of the five reported human H7N9 strains with 37 H7N9 viruses isolated from more than 10,000 poultry market, farm and slaughterhouse samples from across China suggests that the virus would only need small mutations in its protein structure in order to become easily transmissible among humans. Moreover, testing in ferrets—widely considered to the best proxy for humans in flu testing—finds that one lethal strain of the virus that killed the first H7N9 victim in China is transmissible via respiratory droplet, meaning that it could conceivably be spread by coughing and sneezing. The new results are published in Science today. “Our findings indicate nothing to reduce the concern that these viruses can transmit between humans,” says study author Hualan Chen of the CAAS. The new findings are “worrisome,” says Charles Chiu, an infectious disease expert at the University of California, San Francisco. “For this particular virus, for H7N9, whether or not there is human-to-human transmission is a critical question.”
Posted on: Tue, 23 Jul 2013 18:34:27 +0000
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