A new strain of avian influenza A (H7N9) virus has created a human outbreak (130 human infections) that was reported for the first time in China by the World Health Organization on April 1, 2013. The virus was also found in poultry in China as well. It is believed that human infection was due to exposure to infected poultry or similarly contaminated environments. Although there were mild cases reported there were patients who experienced severe respiratory complications and 44 people died.
So far, there has been no reported human-to-human spread and no cases have been reported outside of China. No cases have been reported in birds or humans in the U.S.
The number of cases reported dropped quickly after April in China. This may have been due to containment measures taken by the Chinese government which involved closing live bird markets, or from a change in seasons or perhaps for both reasons. Research demonstrates that avian influenza viruses tend to have a season pattern. If this is the case, it is expected that H7N9 infections will pick up again when the weather becomes cooler in China.
There is some concern that this virus has potential to create a pandemic because influenza viruses are constantly changing (mutating). Therefore, the Centers for Disease Control and Prevention (CDC) in Atlanta, GA, is keeping an eye on the situation not only within the U.S. but globally as well. Whenever, a new virus has been designated as having pandemic potential, the CDC takes action including determining /developing a candidate vaccine in case a vaccine is needed. The CDC has also established guidelines for doctors and public health officials in the U.S. as well as providing information to people who will be traveling to China. Updates will be made as the information changes.
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Current Risk of H7N9 in the United States
It is believed that infection by the H7N9 avian virus in the U.S. is very slight. Currently the CDC has no special recommendations for the public, however, emergence of this new strain of bird flu that has brought about severe illness and death in some people which creates concerns everywhere.
It is known that birds, whether wild water or shore, are hosts to many avian influenza viruses and these viruses are vastly different from human influenza viruses. For that reason, avian influenza doesn’t tend to infect humans making human infection somewhat rare. However, since the avian influenza virus is so different from human influenza virus, humans have very little to no immunity when the avian influenza virus mutates. That’s why, whenever a human becomes infected with a new animal virus (in this case bird, a novel virus), this is of concern because it has the potential to become pandemic as we have little to no immunity against it.
What is currently known about H7N9 is that it contains genetic mutations that have been associated with making bird flu viruses spread more easily to mammals causing severe disease that progresses faster. What this means is that H7N9 starts out with flu-like symptoms such as fever and cough but quickly progresses into severe pneumonia, acute respiratory distress syndrome and multi-organ failure.
Are you Planning to Travel to China?
If you are one of the many who travel between the U.S. and China, the CDC has issued a health alert for doctors and public health authorities in the U.S. to keep an eye out for flu symptoms in travelers. As H7N9 has not been reported to spread easily from human-to-human, the CDC doesn’t recommend that you delay or cancel your trip to China. You should, however, take precautions when in China not to touch birds or other animals. Make sure to eat foods that are well cooked and maintain proper hygiene. If for any reason you experience flu-like symptoms whether during your stay in China or after you come back, consult with a healthcare provider immediately. For updates on travel information, go to CDC Travelers’ Health. For more information on H7N9, please visit Avian Influenza A (H7N9) Virus.
Exactly What is H7N9?
H7N9 is an influenza A virus. The A viruses are divided up into subtypes based on two proteins that are found on the surface of the virus. The proteins include hemagglutinin (HA) and neuraminidase (NA). So, H7N9 identifies the the virus as having HA of the H7 subtype and NA of the N9 subtype. The H7N9 virus is found in birds but doesn’t generally infect humans. The H7N9 virus reported in China is a new strain that is very different from previous H7N9 strains.
The bird influenza A H7 viruses normally are associated with various birds and H7 infections in humans are normally rare, however, H7 virus infections have been reported globally in individuals who have had direct contact with birds that are infected. These infections were reported to be mild involving conjunctivitis and upper respiratory symptoms. Such H7 viruses include H7N2, H7N3 and H7N7. However, in the past, H7N9 had only been isolated in birds with bird outbreaks in Japan, Netherlands and the U.S..
H7N9 has been genetically characterized and it is reported that the virus that can infect humans is the result of recombination between several parent viruses in poultry and wild birds in Asia most closely related to ducks. At any rate, the HA genes are found in the circulating East Asian flyway and the NA genes came from European birds and transferred to ducks in China through migration.
According to Dr. Keiji Fukuda, World Health Organization’s assistant director-general for health security and environment, “I think we are genuinely in new territory here in which the situation of having something that is low path in birds (yet) appears to be so pathogenic in people… And then to have those genetic changes … I simply don’t know what that combination is going to lead to. Almost everything you can imagine is possible. And then what’s likely to happen are the things which you can’t imagine.”
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How does a bird flu virus infection occur?
Although bird flu virus infections are rare in humans, they do occur. This generally involves being in close proximity to infected birds whether live or dead or areas that would be contaminated with virus. Birds that are infected with flu virus can shed avian virus through their droppings or mucus secretions. If you touch an infected bird or contaminated environment and then touch your eyes, nose or mouth, you can be infected with virus. Also, droppings can become sun dried and become airborne where you end up breathing in the virus and become infected that way.
Can H7N9 virus be diagnosed in Humans?
There is a test that was developed by the CDC that can determine whether you have H7N9 and not some other flu virus. The test is available for use by qualified public health labs in the U.S. and globally. A respiratory sample is taken either from the nose, throat or lung and sent to the lab where they run a rRT-PCR (real-time reverse transcriptase polymerase chain reaction). This assay takes about four hours to run and is very accurate at detecting flu viruses.
Can Bird virus be treated in Humans?
At this time, the CDC recommends oseltamivir (Tamiflu) and zanamivir (Relenza, a neuraminidase inhibitor) for individuals who have been infected with H7N9.
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