Zoonotic Influenzas
Definitions & Key takeaways
Zoonotic influenza refers to the influenza viruses circulating in animals, and are also able to infect humans. These viruses can cause respiratory infections that range from mild to severe, and in some cases, they can lead to deadly pandemics. The most well-known zoonotic influenza virus is the H5N1 virus, also known as avian influenza or bird flu, which is primarily found in birds, but can occasionally infect humans who come into close contact with infected birds.
Other examples of zoonotic influenza viruses include swine flu (H1N1), which can be transmitted from pigs to humans, and the recently emerged COVID-19 virus, which is believed to have originated from bats. The prevention of zoonotic influenza transmission to humans includes careful monitoring of animal populations, avoiding contact with sick animals or their feces, and practicing good hygiene, such as frequent hand washing.
Zoonotic influenzas spread around the world in yearly outbreaks, resulting in about three to five million cases of severe illness and approximately half a million deaths.
In humans, they typically cause mild to severe respiratory symptoms and fever, and they also have the potential to cause epidemics or pandemics.
Influenza viruses belong to the Orthomyxoviridae family. They are segmented, negative sense, single-stranded RNA viruses.
Only types A and B cause disease in humans, with type A influenza viruses being the most common. Influenza viruses are classified based on two surface proteins: hemagglutinin, or H protein, and neuraminidase, or N protein, of which there are many different types.
So for example, the H1N1 virus that causes swine flu has H protein type 1 and N protein type 1. Among other things, these surface proteins determine what species the virus can infect.
However, influenza A viruses can undergo antigenic shifts where two strains of the virus mix their genome to create a new virus with a different set of H and N proteins.
This allows the new virus to infect different species from the original strains. The most common types of zoonotic influenzas are avian, meaning originating from birds, and swine, meaning originating from pigs.
Avian flu is caused entirely by influenza A virus and transmission is often through direct contact with infected poultry as the birds are slaughtered or plucked.
Based on pathogenicity, avian influenza is divided into two types: high pathogenicity or low pathogenicity. The type with the greatest risk is highly pathogenic avian influenza, or HPAI.
The most well-known HPAI strain is H5N1, which first appeared in China in 1996, and was then responsible for the bird flu outbreak in 2004.
Other low pathogenic avian influenza viruses include H7N9, H9N2 and most recently H10N8. Swine influenza is also caused by influenza A.
Transmission occurs during close contact with the pig such as during the raising process, transport, or meat-packing. Well known outbreaks include the Spanish Flu in 1918 which was caused by the H1N1 strain, and H3N2 which was responsible for the Hong Kong Flu in 1968.
The symptoms of zoonotic influenzas include fever, dry cough, headache, muscle or joint pain, sore throat, chills, fatigue, and runny nose.
In some severe forms of influenza, the onset of symptoms is characterized by quick clinical deterioration approximately three to five days after first symptom onset.
Some patients quickly progress to pneumonia, respiratory failure and multi-organ failure. Diagnosis of a zoonotic influenza should be considered if a patient presenting with flu-like symptoms has been exposed to a person known to be infected or exposed to birds or pigs in an area with an ongoing avian or swine influenza outbreak, particularly an area with ongoing transmission of virus from domestic poultry or pigs to humans.
Lab diagnosis is done using RT–PCR from a nasopharyngeal swab or washing. Patients with lower respiratory tract illness can have samples taken from endotracheal aspirates or bronchoalveolar lavage fluid.
Throat swabs may be used if other recommended specimens cannot be obtained. Most people with swine or avian flu require only symptom relief, resting, drinking plenty of fluids, and oral NSAIDs or acetaminophen.
However, in some severe cases, antiviral drugs like oseltamivir and zanamivir are prescribed to reduce the severity of symptoms and possibly the risk of complications.
Preventive measures like hand-washing, face masks, proper animal handling, and vaccination are extremely important to avoid zoonotic influenza outbreaks.
##Summary Alright, as a quick recap: Zoonotic influenzas spread around the world in outbreaks and are caused by influenza viruses, which are negative sense, single-stranded RNA viruses.
The most common types of zoonotic influenza are avian and swine, which are caused by type A influenza viruses; common subtypes include H1N1 and H3N2 that cause swine flu and
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