Frequently Asked Questions on human infection caused by the avian influenza A(H7N9) virus
1. What is the avian influenza A(H7N9) virus?
Avian influenza A H7 viruses are a group of influenza viruses that normally circulate among birds. The avian 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 have been reported until recent reports from China.
2. What are the main symptoms of human infection caused by avian influenza A(H7N9) virus?
Thus far, most patients with this infection have had severe pneumonia. Symptoms include fever, cough and shortness of breath. However, information is still limited about the full spectrum of illness that infection with avian influenza A(H7N9) virus might cause.
3. How many human cases of avian influenza A(H7N9) virus have been reported in China to date?
New cases that are reported are now being compiled and posted daily. The most current information on cases can be found in:
4. Why is this virus infecting humans now?
We do not know the answer to this question yet, because we do not know the source of exposure for these human infections. However, analysis of the genes of these viruses suggests that although the viruses have evolved in birds, they may infect mammals more easily than other avian viruses.
5. What is known about previous human infections with H7 influenza viruses globally?
From 1996 to 2012, human infections with H7 influenza viruses (H7N2, H7N3, and H7N7) were reported in Canada, Italy, Mexico, the Netherlands, the United Kingdom, and the United States of America. Most of these infections occurred in association with poultry outbreaks. The infections mainly resulted in conjunctivitis and mild upper respiratory symptoms, with the exception of one death, which occurred in the Netherlands. Until this event, no human infections with H7 influenza viruses have been reported in China.
6. Is the avian influenza A(H7N9) virus different from influenza A(H1N1) and A(H5N1) viruses?
Yes. All three viruses are influenza A viruses but they are distinct from each other. H7N9 and H5N1 are considered animal influenza viruses that sometimes infect people. H1N1 viruses can be divided into those that normally infect people and those that normally infect animals.
7. How are people becoming infected with the avian influenza A(H7N9) virus?
At this point it is not known how persons are becoming infected. Some of the confirmed cases had contact with animals or with environments where animals are housed. The virus has now been found in chickens, ducks, and captive-bred pigeons at live bird markets near locations where cases have been reported. The possibility of an animal source of the infection is being investigated, as is the possibility of person-to-person transmission.
8. How can infection with avian influenza A(H7N9) virus be prevented?
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.
- Wash your hands before, during, and after you prepare food; before you eat; after you use the toilet; after handling animals or animal waste; when your hands are dirty; and when providing care when someone in your home is sick. Hand hygiene will also prevent the transmission of infections to yourself (from touching contaminated surfaces) and in hospitals to patients, health care workers and others.
- Wash your hands with soap and running water when hands are visibly dirty; if hands are not visibly dirty, wash them with soap and water or use an alcohol-based hand cleanser.
- Cover your mouth and nose with a medical mask, tissue, or a sleeve or flexed elbow when coughing or sneezing; throw the used tissue into a closed bin immediately after use; perform hand hygiene after contact with respiratory secretions.
9. Is it safe to eat meat, for example, poultry and pork products?
Influenza viruses are not transmitted through consuming well-cooked food. Because influenza viruses are inactivated by normal temperatures used for cooking (so that food reaches 70°C in all parts -"piping" hot - no "pink" parts), it is safe to eat properly prepared and cooked meat, including from poultry and game birds.
Diseased animals and animals that have died of diseases should not be eaten.
In areas experiencing outbreaks, meat products can be safely consumed provided that these items are properly cooked and properly handled during food preparation. The consumption of raw meat and uncooked blood-based dishes is a high-risk practice and should be discouraged.
10. How can meat be safely prepared?
Always keep raw meat separate from cooked or ready-to-eat foods to avoid contamination. Do not use the same chopping board or the same knife for raw meat and other foods. Do not handle both raw and cooked foods without washing your hands in between and do not place cooked meat back on the same plate or surface it was on before cooking. Do not use raw or soft-boiled eggs in food preparations that will not be heat treated or cooked. After handling raw meat, wash your hands thoroughly with soap and water. Wash and disinfect all surfaces and utensils that have been in contact with raw meat.
11. Is it safe to visit live markets and farms in areas where human cases have been recorded?
When visiting live markets, avoid direct contact with live animals and surfaces in contact with animals. If you live on a farm and raise animals for food, such as pigs and poultry, be sure to keep children away from sick and dead animals; keep animal species separated as much as possible; and report immediately to local authorities any cases of sick and dead animals. Sick or dead animals should not be butchered and prepared for food.
12. Is the source of infection poultry and live poultry markets?
Although some evidence points to live poultry as a source of infection, it cannot yet be confirmed that live poultry is the primary or the only source of infection. Neither is there enough evidence to exclude other possible animal or environmental sources of infection.
13. Can closure of live poultry markets affect the transmission of this virus?
Live markets should be closed briefly on a regular basis for thorough cleaning, with all birds temporarily removed during cleaning. Regular sampling and testing of new batches of birds brought into a live market can help ensure earlier detection of infected birds for removal.
Regular maintenance of live markets also ensures that economic disruption and consumer access to protein sources are minimized, and that the bird trade is not diverted into uncontrolled distribution and sales channels.
The risk of virus transmission can be substantially reduced by applying good market practices. See:
14. Is there a vaccine for the avian influenza A(H7N9) virus?
No vaccine for the prevention of avian influenza A(H7N9) infections in humans is currently available. However, viruses have already been isolated and characterized from the initial cases. The first step in development of a vaccine is the selection of candidate viruses that could go into a vaccine. WHO, in collaboration with partners, will continue to characterize available avian influenza A(H7N9) viruses to identify the best candidate viruses. These candidate vaccine viruses can then be used for the manufacture of vaccine if this step becomes necessary.
15. Does treatment exist for avian influenza A(H7N9) infection?
When influenza antiviral drugs known as neuraminidase inhibitors are given early in the course of illness, they are effective against seasonal influenza virus and influenza A(H5N1) virus infection. At this time, there is little experience with the use of these drugs for the treatment of H7N9 infection. Further, influenza viruses can become resistant to these drugs.
16. Is the general population at risk from the avian influenza A(H7N9) virus?
We do not yet know enough about these infections to determine whether there is a significant risk of community person to person spread. This possibility is the subject of epidemiological investigations that are now taking place.
17. Are health care workers at risk from the avian influenza A(H7N9) influenza virus?
Health care workers often come into contact with patients with infectious diseases. Therefore, WHO recommends that appropriate infection prevention and control measures be consistently applied in health care settings, and that the health status of health care workers be closely monitored. Together with standard precautions, health care workers caring for those suspected or confirmed to have avian influenza A(H7N9) infection should use additional precautions, see:
- Infection prevention and control of epidemic- and pandemic-prone acute respiratory diseases in health care
18. What investigations have begun?
Local and national health authorities are taking the following measures, among others:
- Enhanced surveillance for pneumonia cases of unknown origin to ensure early detection and laboratory confirmation of new cases;
- Epidemiological investigation, including assessment of suspected cases and contacts of known cases;
- Close collaboration with animal health authorities to determine the source of the infection.
19. Does this influenza virus pose a pandemic threat?
An animal influenza virus that develops the ability to infect people could theoretically carry a risk of causing a pandemic. However, whether the avian influenza A(H7N9) virus could actually cause a pandemic is unknown. Other animal influenza viruses that have been found to infect people occasionally have not gone on to cause a pandemic.
20. Is it safe to travel to China?
The number of cases identified in China is low. WHO does not advise the application of any travel measures with respect to visitors to China nor to persons leaving China.
21. Are Chinese products safe?
There is no evidence to link the current cases with any Chinese products. WHO advises against any restrictions to trade at this time.
22. A case was recently confirmed by Taipei CDC. The person traveled from Jiangsu via Shanghai; was he symptomatic during the flight?
No. His symptoms began three days after he took the flight.
23. Could this confirmed case have infected other passengers on the same flight?
It is very unlikely that this case could have infected other passengers. Testing of more than 1000 contacts of other confirmed cases has not yielded any evidence of human-to-human transmission of this virus in the community.
24. What does WHO recommend regarding air travel?
WHO does not recommend any travel restrictions with respect to this event. WHO will continue to provide updated information as it becomes available.
25. What is WHO’s role in this event?
Since the emergence of this virus, WHO has been working under the International Health Regulations to provide information to Member States. WHO is also working with international partners to coordinate the global health response, including risk assessment, the provision of updated information on the situation, guidance to health authorities and technical health agencies on interim surveillance recommendations, laboratory testing of cases, infection control, and clinical management.
WHO will continue to work with Member States and international health partners and share updated information as it becomes available.