New influenza virus detected in China

The Norwegian Institute of Public Health has been notified by international partners that three cases of a new influenza A (H7N9) virus have been confirmed in China. The risk of spread to Norway is considered to be low. There is no change in travel advice for China.

The three patients became ill between 19th February and 15th March; two of them have since died and the third patient is critically ill. They had no known contact with each other. Two of the patients come from Shanghai and the third comes from Anhui province which is located west of Shanghai.

The patients had respiratory symptoms that developed into pneumonia and severe respiratory disease.

One of the three patients had been in contact with poultry. Two family members of one of the deceased patients became seriously ill, and one has since died, although these cases are not laboratory confirmed.

Contact tracing has begun around the proven cases and none of the 88 close contacts who have been examined (apart from the two aforementioned family members) have developed symptoms.

Influenza virus A (H7N9)

The Chinese infectious disease control centre has identified viruses from the three patients as influenza A (H7N9). While there is a large degree of similarity between the three viruses, they differ enough to assume that the patients have different sources of infection.

Analysis shows that the virus is composed of components of several types of avian influenza virus from Asia. A virus with exactly this combination of genes has so far not been detected in birds. A more thorough analysis of the viruses is in progress. Influenza virus subtype A (H7N9) is not usually seen among humans so it can therefore be assumed that immunity is low. It is unknown whether the seasonal influenza vaccine will protect against this new virus.

Laboratory testing

Patients who are hospitalised with severe respiratory disease and who have been in China during the last 10 days should be tested for influenza virus. General recommendations are already in place for testing of patients with severe respiratory disease who may have been infected in areas with confirmed avian influenza virus A (H5N1).

It is expected that the new virus can be confirmed as influenza A by the PCR tests used in medical microbiology laboratories throughout Norway. Upon discovery of influenza A viruses that cannot be subtyped, the sample should be forwarded to the reference laboratory at the Norwegian Institute of Public Health, where further testing will be done, and possibly forwarded to the WHO international reference laboratory.

Travel to China

Travel restrictions to China have not been recommended and the existing guidelines for avian influenza virus A (H5N1) apply.

Risk assessment

The risk of spread to Norway is currently regarded as low but cannot be excluded. As there are currently only three confirmed cases it is difficult to elaborate on the source of infection, infectivity, symptoms and severity of infection with this virus. The Norwegian Institute of Public Health is monitoring the situation closely and will provide updated information and advice as soon as it is available.

Past outbreaks of H7 viruses

The avian influenza virus with subtype H7 has previously infected humans, but it is unknown if it was transmitted between people. Transmission to humans associated with outbreaks in birds was seen in the Netherlands in 2003, in the United Kingdom in 2006, Canada in 2004 and Mexico in 2012. In these cases, conjunctivitis was a distinctive feature. The disease gave mild symptoms with the exception of one fatal case during the H7N7 Netherlands outbreak. However, the new virus is different from previously known H7 and H9 viruses, and may cause other clinical outcomes.

Notification of suspected cases

Health professionals who suspect infection with avian influenza (all types) among patients are requested to notify the Duty Medical Officer by telephone, 21 07 63 48.

More information:
WHO: Frequently Asked Questions on human infection with influenza A(H7N9) virus, China

Risk assessment - European Centre for Disease Control

Provided by Norwegian Institute of Public Health