Human infection with influenza A (H7N9) virus in China
- update
9 APRIL 2013 - As of 9 April 2013 (14:00 CET), the National Health and Family Planning Commission notified WHO of an additional three laboratory-confirmed cases of human infection with influenza A(H7N9) virus.
The latest laboratory-confirmed cases include two patients from Jiangsu – an 85 -year-old man who became ill on 28 March 2013 and a 25-year-old pregnant woman who became ill on 30 March 2013. Both are in severe condition. The third patient is a 64-year-old man from Shanghai who became ill on 1 April 2013, and died on 7 April 2013.
To date, a total of 24 cases have been laboratory confirmed with influenza A(H7N9) virus in China, including seven deaths, 14 severe cases and three mild cases.
More than 600 close contacts of the confirmed cases are being closely monitored. In Jiangsu, investigation is ongoing into a contact of an earlier confirmed case who developed symptoms of illness.
The Chinese government is actively investigating this event and has heightened disease surveillance. Retrospective testing of recently reported cases with severe respiratory infection may uncover additional cases that were previously unrecognized. An inter-government task force has been formally established, with the National Health and Family Planning Commission leading the coordination along with the Ministry of Agriculture and other key ministries. The animal health sector has intensified investigations into the possible sources and reservoirs of the virus.
WHO is in contact with national authorities and is following the event closely. The WHO-coordinated international response is also focusing on work with WHO Collaborating Centres for Reference and Research on Influenza and other partners to ensure that information is available and that materials are developed for diagnosis and treatment and vaccine development. No vaccine is currently available for this subtype of the influenza virus. Preliminary test results provided by the WHO Collaborating Centre in China suggest that the virus is susceptible to the neuraminidase inhibitors (oseltamivir and zanamivir).
At this time there is no evidence of ongoing human-to-human transmission.
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.
About H7N9 Virus
Introduction
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 have been reported until recent reports from
China.
Main
Symptoms with Human Infections
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 disease that
infection with influenza A (H7N9) virus might cause.
Why the
Virus Infecting Human
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 they
have evolved from avian (bird) viruses, they show signs of adaption to growth
in mammalian species. These adaptations include an ability to bind to mammalian
cells, and to grow at temperatures close to the normal body temperature of
mammals (which is lower than that of birds).
Knowledge
on Previous Human Infections with H7 Influenza Virus
From 1996 to 2012, human infections with H7
influenza viruses (H7N2, H7N3, and H7N7) were reported in the Netherlands,
Italy, Canada, United States of America, Mexico and the United Kingdom. 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.
Modes of
Transmission
Some of the confirmed cases had contact with
animals or with an animal environment. The virus has been found in a pigeon in
a market in Shanghai. It is not yet known how persons became infected. The
possibility of animal-to-human transmission is being investigated, as is the
possibility of person-to-person transmission.
Preventive
Measures
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.
About the consummation of Poultry and Pork Parts
About the consummation of Poultry and Pork Parts
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.
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.
About Vaccine
No vaccine for the prevention of influenza
A(H7N9) infections 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 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.
About Anti Viral
Laboratory testing conducted in China has shown
that the influenza A(H7N9) viruses are sensitive to the anti-influenza drugs
known as neuraminidase inhibitors (oseltamivir and zanamivir). When these drugs
are given early in the course of illness, they have been found to be effective
against seasonal influenza virus and influenza A(H5N1) virus infection.
However, at this time, there is no experience with the use of these drugs for
the treatment of H7N9 infection.
Investigations of H7 Virus
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.
About Possibility of Pandemic Threat
Any animal influenza virus that develops the ability to infect people is a theoretical risk to cause a pandemic. However, whether the influenza A(H7N9) virus could actually cause a pandemic is unknown. Other animal influenza viruses that have been found to occasionally infect people have not gone on to cause a pandemic.
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