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Expert of this article: Dr. Tian Jing, CDC, Southern Theater Command, attending physician
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Review of this article: Chen Haixu, Second Medical Center of PLA General Hospital, Deputy Director, Master Supervisor
April 26
Announcement issued by the National Health Commission
A case of human infection with H3N8 avian influenza was found in Henan Province
CDC The patient’s specimen was testedresults wereH3N8 avian influenza viruspositiveby experts It is assessed that this H3N8 avian influenza virus is of avian originhas not yet had the ability to infect humans effectively strong>
Then
H3N8 is a what virus?
How did spread?
How to prevent?
Today, I will give you some popular science.
What are the classifications of influenza viruses?
Influenza virus belongs to the family Orthomyxoviridae, which is a kind of RNA virus. According to the difference of virus matrix protein and nucleoprotein, it can be divided into A, B, C, D, There are four types of influenza viruses, among whichInfluenza A, B, and C viruses can infect humans, and influenza D only infects pigs and cattle.
Influenza A viruses are the fastest evolving and lethal It has the highest rate and often causes pandemics of influenza in the world.
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What kind of virus is H3N8?
Influenza virus has a lipid coating on the surface, and the envelope is composed of hemagglutinin (HA) and neuraminidase (NA). The glycoprotein, which is antigenic, determines the subtype of influenza virus.
Influenza A virus can be further classified into 18 HA subtypes (H1-H18) and 11 NA subtypes (N1-N11).
All strains of influenza A virus have been isolated from wild birds, and currently The most common in humans are the H1, H2, H3, N1 and N2 subtypes.
H3N8 influenza virus is the most common in wild birds A common subtype.
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How does the H3N8 influenza virus spread?
Migration behavior of migratory birds, feeding behavior of birds, and whether resident birds (poultry) are infected are all related to the spread of avian influenza virus.
waterfowl such as waterfowlthe main route of transmission< /span>mainly fecal-oral route;
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poultrytransmission can occur through fecal-oral and respiratory routes to spread;
< strong>mammalsthroughdroplets, aerosols, nasal secretions, etc. way of transmission.
When will avian influenza virus infect humans?
The spread of influenza virus is affected byenvironment, air humidity, temperature, air droplets, etc., Human cases of avian influenza usually involve exposure to poultry or wild birds.
The key to whether the influenza virus can infect the host lies in the ability of the influenza virus to < strong>Whether HA protein can bind to receptors on the surface of host cells.
Influenza A viruses generally tend to bind alpha-2 ,3 receptors, while only a small number of ciliated cells in the human upper airway express α-2,3 receptors, and the vast majority of non-ciliated cells express α-2,6 receptors, butThe epithelium of lower respiratory tract, cornea, conjunctiva and lacrimal gland expresses α-2,3 receptors, which may be the main factor for the cross-species infection of avian influenza virus in humans.
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However, cross-host infection must break through the host’s immune barrier, Innate immunity, humoral immunity and cellular immunity can all limit influenza virus infection.
In addition, HA, NA and other proteins require Evolving under selection pressure and other pressures, and major changes in phenotype, may change the virulence of influenza virus or enable the host range to break through the human barrier.
Can H3N8 be pathogenic in humans?
H3N8 influenza has a wide host range and can infectwild birds, poultry, horses, pigs, Dogs, donkeys, cats, seals, camels and other mammals, and can produce cross-species transmission.
In 2021, it was reported that a strain originating from the East Africa-West Asia migration line was isolated in Xinjiang. A new variant strain of H3N8 influenza virus XJ47 in mallard ducks, which has mutations in several important receptor binding sites, has the ability to infect mammals.It is speculated that It is also likely to have the potential to infect humans across species, suggesting that the H3 subtype avian influenza virus should be paid attention to.
In the case of human infection with H3N8 avian influenza, the H3N8 virus has evolved to be able to cross species. The ability to spread, but no further risk of large-scale transmission has been found.
How to prevent avian influenza virus infection?
1. Avoid contact with live poultry, and do not capture, raise and eat wild birds;
< span>2. Poultry practitioners should do personal protection, wear masks, wash hands frequently, and have regular physical examinations;
3. Pay attention to food hygiene, raw and cooked food should be strictly separated;
4. Improve self-protection awareness. If you have a history of contact with poultry and have respiratory symptoms, you should wear a mask and seek medical attention immediately.
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