Questions and Answers about human infection withA(H7N9) avian influenza virus
2013-03-31

  1. What is A(H7N9) avian influenza virus?

  There are three types of influenza viruses – A, B and C. Human influenza A and B cause seasonal epidemics. The natural reservoir of all influenza A viruses are birds. Influenza A viruses can infect humans, birds, mammals and other animals.

  Influenza A viruses are divided into 2 subtypes, based on viral surface proteins, i.e. hemagglutinin (HA) and neuraminidase (NA). There are currently 16 known HA subtypes (H1-16) and 9 known NA subtypes (N1-9) with many possible combination of HA and NA proteins.

  Influenza AH7 can have 9 subgroups (i.e. H7N1-9) Most H7 viruses identified worldwide were in wild birds and poultry. H7 in humans in uncommon but has een documented in persons who have direct contact with infected birds, especially during outbreaks of H7 virus in poultry.

  From 1996 to 2009, human infections with H7 influenza were reported in Netherlands, Italy, Canada, USA and England, the pathogen of which were H7N2, H7N3, and H7N7, and the cases mostly presented conjunctivitis and mild upper respiratory. So far, there have been no human infections with H7 influenza viruses reported in China.

  More importantly, H7N9 had only been previously isolated in birds, and outbreaks among birds were only reported in Netherlands, Japan and USA.

  2. How many human cases infected with H7N9 influenza virus have been reported in China to date?

  As of 30 March 2013, we report 3 confirmed cases detected in China including 2 fatal cases from Shanghai and 1 case from Anhui who is currently hospitalized. The onset dates of the 3 cases lie between 24-February and 15-March.

  3. What are the main symptoms of human infection with A(H7N9) avian virus?

  The three confirmed cases presented all with acute pneumonia whose symptoms include acute fever onset, high fever, cough and respiratory tract infection symptoms at the early stage of the disease. Five to seven days of disease onset, the patients developed severe pneumonia i.e. breathing difficulties and some progressed rapidly into acute respiratory distress syndrome and death.

  Currently, our knowledge about the clinical characteristics of disease was limited, whether the infection can cause mild or other clinical presentation was still not clear. The understanding of the disease will change accordingly as more information accumulates.

  4. Is the A(H7N9) avian influenza virus like H1N1 and H5N1 seasonal influenza virus?

  As only 3 confirmed cases of human infection with H7N9 influenza virus has identified globally, the research material for the virus itself and the disease it caused are rather limited. The accurate judgments to the virulence and the transmission ability among humans haven’t been achieved yet.

  5. Where has the human infection with A(H7N9) avian influenza virus come from?

  The investigation is ongoing to determine the source of infection of the 3 cases. A(H7N9) virus is an avian influenza viruses, and according to the previous outbreak reports, the source of the human infection with influenza virus A subtype H7 probably is poultry.

  6. Can A(H7N9) avian influenza virus transmitted from person to person?

  Given the limited number of confirmed cases to date, it is still uncertain how this virus is being transmitted from birds. Epidemiology links between the 3 confirmed cases haven’t been discovered. Investigation is ongoing, but so far no further cases were identified among the contacts of the case. Up to date, no subclinical infections have been determined from all the blood taken in contacts. But we cannot rule out the possibility of human to human transmission until we know more about the virus characteristics and results from ongoing investigations.

  7. Has any close contacts become ill or dead?

  According to China’s regulations on management of the unknown pneumonia, the Departments of Health in Shanghai, Anhui and Jiangsu have implemented strictly medical observation to all the close contacts of the confirmed cases. All the close contacts of the confirmed cases from Shanghai and Anhui haven’t show the similar symptom so far.

  8. How to prevent from being infected with A(H7N9) avian influenza virus?

  Influenza is an acute respiratory infection disease. It could be prevented through hands-washing, indoor ventilating, as well as balanced-diet and keeping fit. In order to avoid transmitting the virus to the other person, the nose and mouth should be covered by tissue or handkerchief while sneezing or coughing. In addition, special attention should be paid to keep off the sick and dead poultry and livestock.

  To date, there is no vaccine developed for the prevention of H7N9 influenza virus transmission.

  9. Is there a treatment for the A(H7N9) avian influenza virus?

  Antigenic and genome sequence analyses indicate that the A(H7N9) avian influenza virus is sensitive to the neuraminidase inhibitors anti-influenza virus drugs. The usage of neuraminidase inhibitors anti-influenza virus drugs in the early stage of the infection has been proved to be effective, but whether it is the specific treatment to the A(H7N9) avian influenza virus infection needs further investigation.

  10. What can I do to protect myself?

  Respiratory infection disease such as Influenza could be prevented through hands-washing and covering the nose and mouth while sneezes and coughs. In addition, you should try to keep away from the sick and dead poultry and livestock.

  11. Is general population at risk from the A(H7N9) avian influenza virus?

  The 3 cases are not epidemiologically linked. There is currently no evidence of infection in close contacts, the risk associated with A(H7N9) avian influenza virus to the general population remains low.

  12. Are health care workers at risk from the A(H7N9) avian influenza virus?

  Since health care workers have better chance to contact with patients suffering from infectious diseases than the general population, they should employ the proper infection control measures while diagnosing and treating the patients. When receiving the suspect or confirmed H7N9 cases, the effective infection control measures including standard precautions plus droplet precautions plus contact precautions should be taken properly.

  13. What kinds of the control measures and investigation had been implemented?

  The local health authorities pay high attention to the event. The treatment of patients, field epidemiological investigation, specimen collection and inspection, medical observation to the close contacts, and the enhancement of surveillance for the pneumonia cases of unknown origin have already being carried out.

  After receiving the case reports and the sample collected from the patients, China Center for Disease Control and Prevention had carried out risk assessment for potential spread. The laboratory identification and confirmation have been performed timely. Genetic characteristics of the newly identified virus in humans in currently being analyzed to determine potential factors that can explain transmission from birds to humans.

  Due to constant evolving nature of influenza viruses, China participated in the WHO associated global monitoring of influenza viruses in animals and people. H7N9 as an avian influenza newly discovered in humans, has been reported to WHO under IHR (2005).

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