The Health and Family Planning Commission of Ningbo Municipality, Zhejiang province is reporting two additional human cases of avian influenza A(H7N9), bringing the total cases on the Mainland to 670 since 2013.

H7N9 avian influenza Image/CDC
H7N9 avian influenza

According to health officials (computer translated), the patients are from the Yinzhou District –one of the patients is in critical condition while the other is in stable condition.

There are various types of influenza viruses. Apart from the influenza viruses which can circulate among humans and cause seasonal influenza, many other influenza A viruses are found in birds and other animal species. These viruses are distinct from human seasonal influenza viruses and do not easily transmit to humans.

However, some of these animal viruses may, occasionally infect humans. These are known as novel influenza viruses and avian influenza viruses are one example. Avian influenza is caused by those influenza viruses that mainly affect birds and poultry, such as chickens or ducks. Since the virus does not commonly infect humans, there is little or no immune protection against it in the human population.

However, if an avian influenza virus acquired the capacity to spread easily from person to person, either through adaptation or acquisition of certain genes from human viruses, an influenza pandemic can occur.  Human cases infected with avian influenza A (H5N1, H7N9 and H9N2) viruses have been identified in Hong Kong, Mainland China and other parts of the world, while human infections due to H10N8 and H6N1 viruses have been first reported in Mainland China and Taiwan respectively since 2013.