Apr 2, 2013 (CIDRAP News) – Chinese health officials today reported that the H7N9 influenza virus has been detected in four more people, all in critical condition, raising the number of patients infected with the new strain to seven.
All of the patients are from Jiangsu province, an area on China's eastern coast that borders the city of Shanghai and Anhui province, the two areas that reported the first three H7N9 cases, which included the deaths of two men from Shanghai.
A statement today from the Jiangsu Province Health Department, identified and translated this morning by the Avian Flu Diary blog, said all four patients—three women and a man—are in critical condition at hospitals in Nanjing, Wujiang, and Wuxi.
One is a 45-year-old woman from Jiangning district who worked as a poultry slaughterer. She became ill with a fever, body aches, and other symptoms on Mar 19 and was hospitalized on Mar 27. The second patient, a 48-year-old woman from the city of Suqian who is a sheet metal worker, got sick with similar symptoms on Mar 19 and was hospitalized on Mar 30.
The man who was infected is an 83-year-old resident of Suzhou Wujiang district who came down with a fever and respiratory symptoms on Mar 20 and was hospitalized on Mar 29. The fourth patient is a 32-year-old woman from the city of Wuxi who is unemployed. She started having a cough, fever, and other symptoms on Mar 21 and was hospitalized on Mar 28.
The Jiangsu Provincial Center for Disease Control and Prevention detected the H7N9 virus in samples from the patients, and tests at China's Center for Disease Control and Prevention (China CDC) lab confirmed the results for the first two cases.
A statement on the four new cases today from Hong Kong's Centre for Health Protection (CHP) said China's National Health and Family Planning Commission has verified the cases. It added that no epidemiologic links have been found between the four patients and so far no other H7N9 infections have been identified in 167 of their close contacts.
The CHP advised travelers, especially those returning from Shanghai, Anhui province, and Jiangsu province, who have respiratory symptoms to wear face masks, seek medical attention, and share their travel histories with their doctors. It also urged healthcare workers to take extra precautions with travelers who may have had contact with poultry in the three areas.
Yesterday Chinese health officials said the source of the infections is probably poultry. The H7N9 virus has previously infected only birds, though other H7 subtypes have been known to infect humans, typically causing conjunctivitis and mild respiratory symptoms.
In another statement today, the CHP said it activated Hong Kong's pandemic alert response level, which triggers certain surveillance and control measures. The alert level is the lowest response category. The next level is serious, and the highest is the emergency level.
The city of Shanghai has activated its emergency response plan, based on two recent infections and deaths from H7N9 in the area, and health officials in Beijing have stepped up their surveillance for hospitalized cases of avian flu and pneumonia from unknown cases, The Standard, an English-language daily newspaper in Hong Kong, reported today.
The World Health Organization (WHO) today published a frequently-asked-questions resource about H7N9 on its Web page, which emphasized that so far health officials have found no evidence of human-to-human spread, though investigators are exploring all possible sources.
"The risk associated with A (H7N9) avian influenza virus to the general population in China and beyond is being investigated and will be shared to the public when information becomes available," the WHO said.
Les Sims, BVSc, an Australia-based animal health consultant with extensive experience with avian flu in Asia, told CIDRAP News that it's still too early to draw firm conclusions about the virus, but the history of avian flu viruses in the region and the apparent pattern of the human cases suggest that some or even most of the cases are likely the result of virus transmission from animals to humans.
Sims said his early review of genetic evidence in the public domain strongly suggests that the virus originally came from poultry. "In my view, it is only a matter of time before infected poultry will be detected," he said.
Avian infections with low-pathogenicity H7 viruses with a different neuraminidase (N) subtype have been reported in China and the broader region in the recent past, but genetic information suggests that the H7N9 virus marks the first detection of an H7 virus with internal genes from H9N2 viruses.
"The evidence I have seen suggests the virus is probably a low pathogenicity strain for poultry and if circulating in poultry would not necessarily be causing severe disease, which has implications for surveillance programs," Sims said. In contrast, mass poultry deaths in H5N1 are events that signal an imminent threat to humans.
Sims said he's not aware of any poultry vaccination programs for H7 viruses in Asia, except for Pakistan, where vaccines were used to battle a highly pathogenic H7 virus.
A news story in Nature today reported other preliminary analyses of H7N9 genetic sequences from virology experts. It reported that Chinese researchers have sequenced isolates from the first three human cases and posted them to the GISAID flu sequence database. Masato Tashiro, MD, PhD, director of the WHO Collaborating Center for Reference and Research on Influenza at Japan's National Institute of Infectious Diseases in Tokyo, told the journal that his initial assessment is "worrisome," because the virus shows several features that suggest adaptation to humans.
Tashiro said the new virus appears to be a reassortment of three virus strains that infect only birds, according to the report. He told Nature that the N protein is similar to its counterpart in H11N9 viruses found in South Korea, China, and the Czech Republic, and the gene for the hemagglutinin (H) protein—which plays a role in binding to host cells—appears to belong to a Eurasian H7 avian flu group.
Researchers said early analysis suggests the virus has developed mutations that allow the H protein to attach to receptors in mammalian airway cells rather than those in poultry airways, according to the Nature report. They also said early studies suggest that H7N9 can infect cells in the lower airways, which can contribute to severe disease but also can limit the spread of the disease through coughing and sneezing.
Apr 2 Avian Flu Diary post
Apr 2 CHP statement
Apr 2 CHP statement on control measures
Apr 2 Standard story
Apr 2 WHO H7N9 FAQ
Apr 2 Nature news story
Apr 1 CIDRAP News story "China reports three H7N9 infections, two fatal"