Human infection with avian influenza A(H7N9)
Avian influenza A(H7N9) is a virus that normally infects birds, causing them little to no illness. It is one subgroup among the larger group of H7 avian influenza viruses. Until recently, this virus had never been detected in birds, animals or humans. The first reports of human infections with this new strain, detected in China, were reported to WHO on 31 March 2013. Latest information and situation updates are posted on WHO's Disease Outbreak News.
Source of the infection
It is considered likely that the new A(H7N9) viruses stem from a reassortment of three virus strains that infect only birds.
It is likely that many of the people who have been infected with A(H7N9) virus were infected through contact with infected birds. Most of the individuals who have been confirmed with the virus have had contact with animals or with an animal environment, but it is not yet known how persons became infected. The possibility of animal-to-human transmission is being investigated, as is the possibility of person-to-person transmission.
Symptoms and treatment
Thus far, most patients with this infection have developed severe pneumonia. Symptoms include fever, cough and shortness of breath. Information is still limited about the full spectrum of disease that infection with influenza A(H7N9) virus might cause.
Laboratory test results provided by WHO collaborating centres for reference and research on influenza in China and the United States suggest that the virus is susceptible to the neuraminidase inhibitors oseltamivir and zanamivir.
Active investigation and response
The Chinese Government is actively investigating the situation and has heightened disease surveillance to ensure early detection, diagnosis and treatment. WHO headquarters is in contact with national authorities in China and is following the situation closely. WHO/Europe and other WHO regional offices remain alert for the possible appearance of other cases, and are on standby to assist if necessary.
In addition, WHO/Europe is working closely and coordinating efforts with partners, including the European Centre for Disease Prevention and Control (ECDC), and is contributing to global and regional risk assessment. It is also working with the WHO Collaborating Centre for Reference and Research on Influenza in London, United Kingdom, the ERLI-NET and national influenza centres in the European Region to review capacities for diagnosis of infections with the A(H7N9) virus and to provide testing protocols and algorithms.
The WHO-coordinated international response is also focusing on work with WHO collaborating centres for reference and research on influenza and other partners, to ensure that information is available and that materials are developed for diagnosis, treatment and vaccine development.the invitation of the National Health and Family Planning Commission of China, WHO convened a team of experts that visited areas affected by avian influenza A(H7N9) in China 18-25 April 2013 in order to provide recommendations on the prevention and control of the disease.
Although both the source of infection and the mode of transmission are uncertain, it is prudent to follow basic hygienic practices to prevent infection. They include hand and respiratory hygiene and food safety measures.
At present, WHO does not advise special screening at points of entry with regard to this event, or recommend that any travel or trade restrictions be applied.