Chinese authorities made an initial notification of three cases of human infection with influenza A (H7N9) virus to the World Health Organization (WHO) last Sunday. The notification stated that the patients had caught the virus between February 19 and March 15 and that the infection led to death in two cases initially. The Chinese health authorities again notified the WHO yesterday of an additional four laboratory-confirmed cases of human infection with the H7N9 virus in the eastern part of China around Shanghai and nearby provinces.
As of today, Chinese media has reported 14 cases of the virus, including 6 deaths. More than 400 close contacts of the confirmed cases are being closely monitored. Thus far, none of the 400 close contacts have developed any symptoms of illness. Most patients reportedly worked in direct contact with birds in the poultry industry.
The H7N9 influenza virus is one subgroup among the larger group of H7 viruses. Although some H7 viruses have occasionally been found to infect humans, no human infections with H7N9 virus have been reported until the recent reports from China. WHO has said the current bird flu strain hitting China should not be cause for panic at this point since it has yet to be proven that it was transmitted from human to human. WHO is investigating the source of the infection and how it was transmitted to humans.
Other strains of bird flu, such as H5N1, have been circulating for years and can be transmitted from bird to bird and bird to human, but not generally from human to human. It is possible that the new bird flu virus may persist in animals and occasionally occur in humans, but not develop the capacity to spread in humans, said Joe Bresee, chief of epidemiology for the U.S. Center for Disease Control and Prevention (CDC) influenza division.
Lu Huongzhou, a professor at Shanghai Public Health Clinical Center, told Chinese media in an interview today that H7N9 is not especially harmful among birds hosting the disease, but is potentially more dangerous for humans, who have no resistance to the virus.
CDC said it is “following the situation closely and coordinating with domestic and international partners in a number of areas,” including evaluating the public health risk and developing a candidate vaccine virus. Flu experts in laboratories around the world are studying the DNA sequence data of samples isolated from patients to assess the severity. The Stockholm-based European Center for Disease Prevention Control said in an April 3 report that the virus is a combination of H7N9 virus that circulates in birds and an H9N2 pathogen. One of the earliest infections was in a pork butcher, according to the report.
Authorities in Shanghai have discovered the H7N9 virus in a pigeon sample taken from a traditional wholesale market. Shanghai’s city government announced Friday that all live poultry markets in the city would be closed as of tomorrow. No reopening has been announced. Markets in the Songjiang and Minhand districts were closed yesterday. The city has destroyed 20,536 birds so far, an official in Shanghai’s agriculture commission told the media. The Chinese government has stated it has heightened its disease surveillance. An inter-government task force has been formally established with the National Health and Family Planning Commission leading the coordination along with the Ministry of Agriculture and other key ministries. The animal health sector has intensified investigations into the possible sources and reservoirs of the virus.
Meanwhile, Japan and Hong Kong have stepped up vigilance against the virus and are also taking precautions at airports. Posters and personnel are warning passengers to seek medical attention if they suspect they have bird flu. In Hong Kong, authorities activated the preliminary “Alert Responses Level” under a preparedness plan for influenza pandemic, which calls for close monitoring of chicken farms, vaccination, culling drills, and a suspension of imports of live birds from the mainland. Vietnam has banned all forms of transport, trade, and consumption of poultry via its northern border with China, and Taiwan has set up a monitoring group.
