Disease Outbreak AlertsHuman infection with novel influenza A (H7N9) virus, 9 May 2013 UpdateBackground Influenza A H7 viruses are a group of influenza viruses that normally circulate among birds. The influenza A (H7N9) virus is one subgroup among the larger group of H7 viruses. Although some H7 viruses (H7N2, H7N3 and H7N7) have occasionally been found to infect humans, no human infections with H7N9 viruses had ever been reported until cases were detected in China on 29 March 2013 (http://www.who.int/csr/don/2013_04_01/en/index.html). The first case of disease was identified on 19 February 2013, reported from an 87 year old man who developed a respiratory infection and died on the 4 March 2013. Update on case numbers Since our last update on 30 April 2013(http://www.nicd.ac.za/?page=alerts&id=5&rid=225), 7 new cases of avian influenza A(H7N9) including 8 deaths have been confirmed. This brings the total of confirmed human cases of novel influenza A (H7N9) infection, as of 8 May 2013, to 131 including 32 deaths. Of these 130 were from mainland China and one was from Taiwan. (http://www.who.int/csr/don/2013_05_08/en/index.htm). Clinical presentation Symptoms of A (H7N9) are influenza-like, including fever, cough and shortness of breath. Most cases presented with respiratory tract infection that progressed to severe pneumonia associated with breathing difficulties in some cases. However, information is still limited about the full spectrum of disease that infection with influenza A (H7N9) virus might cause. In a pattern seen throughout the outbreak so far, most of the newly reported cases are in men and many of the patients are older. Source of infection and transmission The source and mode of transmission remain unknown, but increasing evidence is pointing to poultry exposure. Investigations into the possible sources of infection and reservoirs of the virus are ongoing. So far there is no evidence of sustained human-to-human transmission. Precautions and infection prevention and control considerations The World Health Organization (WHO) does not advise special screening at points of entry with regard to this event, nor does it recommend that any travel or trade restrictions be applied. Additional information and resources on human infection with influenza A(H7N9) 1. Human infection with influenza A(H7N9) virus in China, http://www.who.int/csr/don/2013_04_01/en/index.html 2.Frequently Asked Questions on human infection with influenza A(H7N9) virus, China accessed at: http://www.who.int/influenza/human_animal_interface/faq_H7N9/en/index.html 3.WHO website: http://www.who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html 4.NICD Website: http://www.nicd.ac.za/
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