Update as of 10 April 2013 
Note that this document supersedes the previous version. Updates will be posted as new information becomes available.
1. What is influenza? [New]
Influenza, or simply flue, is an acute viral infection. Influenza is characterized by a sudden onset of intolerance of cold, shiver, high fever with a temperature of 39-40℃, headache, muscle and joint pain, severe malaise (feeling unwell), and appetite decrease. Commonly there are symptoms including sore throat and cough (usually dry). And nasal obstruction and runny nose could also happen. If with no complication, patients will have symptoms lightened within 3-4 days, but recover from cough and physical power within 1-2 weeks. Symptoms of mild cases are similar with those of common cold, and can be recovered with 2-3 days.
2. What is avian influenza? [New]
Avian influenza, commonly called bird flu, is an infectious viral disease of birds. Avian influenza viruses are divided into three groups based on their ability to cause disease in poultry: high pathogenicity, low pathogenicity and no pathogenicity. So far, only virus subtypes H5 and H7 are found of high pathogenicity. Avian influenza viruses do not normally infect humans due to species barrier. However, there have been instances of certain strains (H5N1, H9N2, H7N2, H7N3, H7N7, H5N2 and H10N7) causing various diseases, including diseases with respiratory symptoms and conjunctivitis, and even death in humans. Human infection with high pathogenic avian influenza H5N1 virus generally presents with respiratory symptoms like high fever, then usually develops pneumonia, sometimes acute respiratory distress syndrome and systemic organ dysfunction, and even death.
3. What is avian influenza A(H7N9) virus? [Updated]
 There are three types of influenza viruses – A, B and C. 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. A total of 144 influenza viruses exist based on inter-combination of HA subtypes and NA subtypes.
The natural reservoir of all influenza A viruses are birds, particularly water birds. Avian influenza A(H7N9) virus is one kind of influenza A virus. It is previously only isolated in birds, and outbreaks among birds were only reported in Netherlands, Japan and USA. No human infection with H7N9 virus has been reported before.
4. How many human cases infected with avian influenza A(H7N9) virus have been reported in China to date? [Updated]
As of 9 April 2013 (18:00 Beijing Time), a total of 28 confirmed cases of human infection with avian influenza A(H7N9) virus have been reported from 4 provinces in China, including Shanghai (13 cases, 5 deaths), Jiangsu (8 cases, 1 death), Anhui (2 cases, 1 death) and Zhejiang (5 cases, 2 deaths). Nine have died. This is the first time human infection with avian influenza A(H7N9) virus has been detected in the world.
 
5. What are the main symptoms of human infection with avian influenza A(H7N9) virus? [Updated]
Patients typically present with influenza-like illness (ILI) symptoms such as fever, cough with little to no sputum production, and accompanied by headache, muscle pain and general malaise. Severe pneumonia can develop rapidly in severe cases and patients have a persistent body temperature over 39℃, difficulty breathing, and may be accompanied by hemoptysis. Some rapidly progress to the acute respiratory distress syndrome (ARDS), shock, multi-organ dysfunction syndrome and even to death. 
Thus far, there is limited knowledge on the clinical characteristics and virus infection spectrum. One of the total 28 cases manifests with ILI symptoms, indicating that some proportion of mild cases may exist in the population. However, whether other clinical manifestations might be caused by avian influenza A(H7N9) virus is still unknown.
The understanding of the disease will change accordingly as more information accumulates. 
6. What are previous global avian influenza H5N1 infections?
From 1996 to 2009, human infections with A(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.
7. What about the virulence and infectivity of H7N9 virus compared to previous H1N1, H5N1 and other seasonal influenza virus? [Updated]
25 of the total 28 confirmed cases had developed severe pneumonia and 9 had died, this indicates the strong virulence of H7N9 virus.
H7N9 virus may have stronger transmission ability from poultry to human seeing that many human infections with avian influenza A(H7N9) virus occur in multi-regions within a short time. Based on the data available, no evidence so far indicates that Avian influenza A(H7N9) virus has the ability of human-to-human transmission. 
8. Where has the human infection with Avian influenza A(H7N9)virus come from? [Updated]
The avian influenza A(H7N9) virus infecting people is determined biologically as avian-origin virus. And most previous human infection with influenza viruses subtype H7 is avian-origin. According to the epidemiological investigation of current confirmed cases, live poultry market exposure is considered to be one risk factor. Poultry with virus and its feces as well as secretion could be the possible source of the infection. Ongoing cooperation on epidemiological investigation by NHFPC and MOA is to be undertaken to identify more risk factors. 
9. Can Avian influenza A(H7N9)virus transmitted from person to person? [Updated]
 To date, there is no evidence of sustained human-to-human transmission of H7N9 virus. 
According to Protocol for Prevention and Control of Human Infections With Avian Influenza A (H7N9) (1st edition, 2013), health authorities of Shanghai, Jiangsu, Zhejiang and Anhui have taken medical observations of all close contacts of confirmed cases. As of 9 April 2013, no infection with avian influenza A(H7N9) virus was found among these close contacts according to medical observation and preliminary laboratory testing results.
Further investigations will be conducted to identify if there exists limited human-to-human transmission among those family cluster cases and cases without animal exposure. There are two possible reasons for the cluster, one is human-to-human transmission via continuous close contact, the other is the exposure to common or respective environmental source of infection such as birds, and etc. 
10. How can infection with avian influenza A(H7N9) virus be prevented? [New]
Current evidence shows that the live poultry market exposure is one of risk factors for human infection with avian influenza A(H7N9). Poultry with virus and its feces as well as secretion could be possible sources of the infection. Therefore, it is prudent to follow the practices in daily life to prevent being infected. 
1) In daily life, try to avoid direct contact with live poultry, birds, esp. sick/dead birds, and their feces. If did, it is a must to wash hands with soap and water as soon as possible. Children should avoid direct contact with poultry and wild birds. Once sick/dead birds or livestock are found, you shall report it to relevant departments rather than handle them by yourself.
2) Do not purchase live poultry and butcher it by yourself; do not contact with or eat sick/dead birds or livestock; do not purchase fresh, live or frozen birds or livestock as well as relevant products without quarantine certificate. 
3) Meat of poultry and livestock shall be fully cooked and eggs are hard-cooked.
4) Follow food safety precautions. Separate raw and cooked when preparing and eating food. Avoid cross contamination. Chopping board, knives and containers used to deal with poultry and livestock meat shall not be used to handle cooked food. Sufficiently wash your hands after preparing poultry and livestock meat as well as eggs.
5) Healthy life style is crucial to prevent infection with H7N9 virus. Regular physical exercises and more rest are good for prevention. Overstrain shall be avoided. Do not smoke. Wash your hands frequently and maintain good personal hygiene. Cover your mouth and nose with a mask or tissue when coughing or sneezing.
6) If fever and respiratory symptoms occur, you shall put on a mask and see your doctor as soon as possible. Remember to tell your doctor about your travel or poultry exposure history before disease onset. Take medication and receive treatment under the supervision of your doctor.
11. Is it safe to eat meat, i.e. poultry and pork products? [New]
Influenza viruses can be inactivated at high enough temperature, and can be killed when food is cooked (at least reaches 70°C in all parts— "piping" hot — no "pink" parts). It is safe to eat properly prepared and well cooked meat, including those from areas where confirmed cases were detected. 
Dead animals and animals that have died of diseases should not be eaten. 
12. Is there a vaccine for the avian influenza A(H7N9) virus? [Updated]
No vaccine for the prevention of avian influenza A(H7N9) infections is currently available. Research and development of vaccine have been initiated.
13. Is there a treatment for the avian influenza A(H7N9)virus? 
 Antigenic and genome sequence analyses indicate that the avian influenza A(H7N9) 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 avian influenza A(H7N9)virus infection needs further investigation. 
14. What approaches have been taken to detect human infection cases with avian influenza A(H7N9) virus? [New]
Local and national health authorities are taking the following measures to detect infected cases, among others:
？ Based on surveillance system for pneumonia cases of unknown origin, identify surveillance cases that meet the definition of human infection with avian influenza of A(H7N9) virus, collect corresponding specimen and send it to laboratory for further confirmation.
？ In provinces already reported human infection with avian influenza A(H7N9) virus, add H7 nucleic acid assay into regular testing items for influenza-like illness (ILI) surveillance so as to detect potential infection at early stage or mild cases. In other provinces, when non-seasonal influenza virus is identified through ILI regular surveillance, further testing of novel subtype H7N9 virus will be conducted.
15. Is general population at risk from the avian influenza A(H7N9) virus? [Updated]
As it is an emerging infectious disease, our knowledge is limited. Current evidences indicate that the A(H7N9) virus most probably comes from birds. The virus distribution scope among the bird species in China is still not clear, and the birds do not have symptoms of illness once they are infected with A(H7N9) virus. It is predicted that more cases might be detected in more areas in the near future as the disease surveillance is being enhanced.
To date, not too many cases have been detected, and they are limited in some provinces/municipalities. No infection is confirmed among the close contacts during medical observations. Although avian influenza A(H7N9) virus may have stronger transmission ability from poultry to human comparing with H5N1 virus, no evidence shows that it has sustained human-to-human transmission ability. Different public infection risks may exist in different areas and situations. Generally, there is fairly low risk for the general population to be infected with avian influenza A(H7N9) virus.
We do not yet know enough about these infections, thus the risk possibility is the subject of dynamic risk assessment which is now taking place.
16. Are health care workers at risk from the avian influenza A(H7N9)virus? [Updated]
To date, there is no clear evidence of sustained human-to-human transmission. No infection has been found among the health care workers who are caring the 28 laboratory-confirmed cases. Since health care workers have better chance to contact with patients suffering from infectious diseases than the general population, they should take 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, droplet precautions and contact precautions should be taken properly. 
17. Who need special protection? [New]
Workers closely in contact with poultry, including those who are working in the field of poultry breeding, cultivation, sorting, transporting, selling, butchering and vaccination, workers handling sick/dead poultry, and professional technicians dealing with terminal sterilization of relevant places need special protection. Protective clothing (isolation gown) shall be put on outside the normal working uniform. Protective masks, disposable latex gloves and high-sleep boots/protective foot cover shall be used. Frequent hands washing will reduce the chance of being infected.
18. Does this influenza virus pose a pandemic threat? [New]
Any animal influenza virus that develops the ability to infect people is a theoretical risk to cause a pandemic. However, whether the avian influenza A(H7N9) virus could actually cause a pandemic is unknown as there is still no evidence of sustained human-to-human transmission. It is still necessary to enhance virus surveillance, outbreak surveillance and dynamic risk assessment.