Since it was first discovered in late March of this year, the H7N9 virus has infected 60 people, killing 13. It’s not clear whether the virus can spread from person to person. But as the first round of tests on the virus has shown, it has some troublesome characteristics.
Scientists from around the world have been busy studying the virus now that its genome has been sequenced.
Research by He Jianku of South University of Science and Technology of China suggests it can change rapidly; a protein that binds H7N9 to its host’s cells may be mutating at a rate eight times faster than in a typical flu virus. He found dramatic mutations of haemagglutinin in one of the four flu strains released for study by the Chinese government; nine of the protein's 560 amino acids had changed. Typically, only one or two amino acids change in such a short period of time.
Nature News is reporting that the new virus has several mutations which make it more adapted to humans than H5N1. According to Jeremy Farrar, director of the Oxford University Clinical Research Unit in Ho Chi Minh City, Vietnam, “This looks very different from H5N1. We never saw this number of presumed avian/animal to human transmissions in such a short space of time."
Adding insult to injury, H7N9 doesn’t appear to cause serious illness in poultry and other birds, making it difficult to detect, track, and control. Chinese officials have developed a test to detect the virus in humans, but no such test currently exists in North America.
A paper published in the New England Journal of Medicine described H7N9 as a “novel reassortant influenza A” virus with genetic similarities to strains found in three different birds — a Beijing finch, and ducks from Zhejiang Province and Korea. The paper’s authors don’t know how the new strain developed, but there’s no evidence the genetic reassortment occurred in a mammalian host. And indeed, given how similar the human virus is to the three avian strains, it was probably transmitted directly by birds.
The NEJM paper also noted that the virus spreads more easily to people than similar viruses, claiming that “The gene sequences also indicate that these viruses may be better adapted than other avian influenza viruses to infecting mammals.”
And once in humans, it's anything but pleasant. Writing in Forbes, Melanie Haiken describes its effects:
In an analysis of the virological data and circumstances surrounding the first three fatalities, a large team of Chinese researchers found that the patients became ill quickly, developed very severe pneumonia and upper respiratory distress, and their condition deteriorated very quickly with sepsis and failure of multiple organs. Particularly worrying is that two of the three developed encephalopathy, or infection of the membrane surrounding the brain.
Some of the background information in the report also offers reason for concern. Yes, all three of the victims had previously existing health conditions; one had COPD, and two had hepatitis B. One was obese. But while one patient was 87, the other two were only 27 and 35. And while two of the three had had contact with poultry in the weeks before falling ill (one was a butcher, the other had been in a poultry shop), one had no record of contact with birds.
Lastly, developing a vaccine for H7N9 could prove difficult. Clinical trials of vaccines designed to protect against other viruses in the H7 family have shown that vaccines don't induce much of an immune response, even when people are given what would be considered very large doses.
That said, Sinovac Biotech Ltd. is planning to develop immunizations against the virus, which they hope to have ready for commercial use by July. But that’s months away. Given the virus's frightening rate of spread, that could prove to be a serious problem.
Top image via China.org.cn. Inset images via ECDC.