Avian and other zoonotic Influenza (Flu) is an infectious or contagious respiratory disease caused by influenza viruses or flu viruses that infect the throat, nose, and sometimes the lungs.
Influenza viruses are from the family Orthomyxoviridae, and these families represent enveloped viruses, and the genome consists of eight segments of negative-sense single-strand RNA.
Avian and other zoonotic Influenza viruses are mainly transmitted from animal to human and not transmitted between human to human. Flu or influenza is either seasonal or zoonotic.
Seasonal means some are spared or effect during a particular season (seasonal flu), and zoonotic means disease, which is transmitted from animal to human (zoonotic influenza).
Type of Flu or Influenza virus
Influenza viruses are categorized as influenza A viruses, influenza B viruses, influenza C viruses, and influenza D viruses.
Influenza A virus
Influenza A virus causes epidemics and pandemics and can affect many species like pigs, birds, humans, horses, etc. Influenza A virus can be subtype according to the combinations of the hemagglutinin (HA) and the neuraminidase (NA).
The viruses that we consider as zoonotic influenza viruses are viruses that are circulating in animal populations, so for example, there are avian influenza viruses, H5N1, H7N9, or H5N6.
Pigs or swine also have their influenza viruses and, they are typical subtypes H1N1, H1N2, or H3N2. Again, not to be confused with seasonal viruses that may look the same as H1N1 and H3N2.
Human cases with these known zoonotic influenza viruses have been reported from about 20 countries around the world.
Influenza B virus
Type B can also cause epidemics (less severe than A). It is responsible for substantial outbreaks every 2-3 years, but it has not caused pandemics.
Influenza C virus
Type C influenza causes mild illness in humans, and No epidemics or pandemics take place.
How to Flu Spread or mode of transmission of influenza
There are two modes of transmission one from animal to human and, second is from human to human.
Luckily most of the human cases with these zoonotic influenza viruses occur from animal to human transmission. Meaning the person is infected with the influenza virus from contact with an infected animal.
Contact meaning touching the birds; contact with the bird’s body during slaughtering or processing, coming into contact with the blood the feces or any other secretions from infected animals.
The second mode of transmission again very rare is that one human is infected with these viruses and can spread that virus directly to another human.
Risk factor for Avian and other zoonotic influenza
Avian influenza virus
The primary risk factor for the human being is direct and indirect contamination with the infected alive or dead bird or poultry and contaminated environments, such as live bird markets.
For avian influenza virus A (H5N1) infections in humans, the incubation period is 2-5 days ranging up to 17 days. And for A (H7N9) virus, the incubation period ranges from 1 to 10 with an average incubation period is five days (For both the virus, the incubation period is more than seasonal influenza that is two days).
Swine influenza virus
In the case of the swine influenza virus, the risk factor is direct or indirect contamination with infected pig or visiting locations where pigs are exhibited. And in some cases, a limited human to human transmission has occurred.
The incubation period of swine flu influenza ranges from 2-7 days.
Older people with compromised immune systems and those with underlying medical conditions such as heart disease, kidney disease, diabetes, chronic lung disease, and cancer are at higher risk of severe illness.
Symptoms of Avian and other zoonotic influenza viruses
Avian, swine and other zoonotic influenza diseases in humans may range from mild upper respiratory infection to r severe pneumonia, acute respiratory distress syndrome, shock, and in some cases, causes death also.
The A(H5N1) infection can cause gastrointestinal disease, and symptoms include nausea, vomiting, and diarrhea.
Patients who are infected by A(H5) or A(H7N9) avian influenza viruses show aggressive symptoms. Initially show high fever and cough followed by signs of lower respiratory tract involvement, including difficulty breathing and dyspnoea.
Upper respiratory tract symptoms include coryza, and sore throat is less common. Other symptoms include diarrhea, vomiting, abdominal pain, bleeding from the nose or gums, encephalitis, and chest pain, etc.
And in case of severe case symptoms reported pneumonia, septic shock, multi-organ dysfunction, hypoxemic respiratory failure, and secondary bacterial and fungal infections.
Diagnosis of Avian and other influenza viruses
Typically a sample is obtained from a patient and, we observe in this sample some parts of the virus. So with either PCR polymerase chain reaction, which detects pieces of the virus.
We can also try to get a sample from the person and try to culture that sample so that we can grow the virus. It is essential because when we have the entire virus, we can then do further studies on it to try to get more information on how it is transmitted or if it’s resistant to antivirals. It can give us a lot of other clues about the disease.
But it’s really important to have two samples of blood to look for antibodies, and one sample is not enough we need to know that the initial sample the antibody level is low and, then it’s gone up in the second sample after some time.
Samples testing positive or which are unsubtypeable should be forwarded to WHO Collaborating Centres for further characterization.
Countries with reduced laboratory diagnostic capacity in place can send clinical specimens from suspected cases to a WHO CC or a laboratory as guided by the WHO.
Treatment of Avian and other zoonotic influenza viruses
Several drugs can be used to treat these infections. The most important things are that these should be given very quickly after symptom onset to have the best benefit possible. And again, other treatment options depend on the condition of the case.
If a person has pneumonia and they aren’t able to breathe on their own very well, they may need to have a tube in their throat, and they may need to have artificial ventilation to support their lungs while they heal, while they recover from the infection.
Prevention of Avian and other zoonotic influenza viruses
Vaccination is a very important tool for seasonal influenza, but there is no good vaccine for these non-seasonal influenza viruses. For a few subtypes, there are vaccines, but they’re not widely available.
Practice good hygiene, especially regular hand washing, before and after touching animals at farms, markets, or other places where animals may be present.
Avoid direct and indirect contact.
Avoid the consumption of undercooked and raw animal products.
Summery
Influenza (Flu) is an infectious or contagious respiratory disease caused by influenza viruses that infect the throat, nose, and sometimes the lungs. Influenza viruses are from the family Orthomyxoviridae Influenza viruses are categorized as influenza A viruses, influenza B viruses, influenza C viruses, and influenza D viruses. Avian and other zoonotic Influenza viruses are mainly transmitted from animal to human and not transmitted between human to human. Flu or influenza is either seasonal or zoonotic. The incubation period is two days, but it can be as short as 1 - 5 days. Influenza A virus causes epidemics and pandemics and can affect many species like pigs, birds, humans, horses, etc. There are two modes of transmission one from animal to human and, second is from human to human. The viruses that we consider as zoonotic influenza viruses are viruses that are circulating in animal populations, so for example, there are avian influenza viruses, H5N1, H7N9, or H5N6. Pigs or swine also have their influenza viruses and, they are typical subtypes H1N1, H1N2, or H3N2. Again, not to be confused with seasonal viruses that may look the same as H1N1 and H3N2. The primary risk factor for the human being is direct and indirect contamination with the infected alive or dead bird or poultry and contaminated environments, such as live bird markets. For avian influenza virus A(H5N1) infections in humans, the incubation period is 2-5 days ranging up to 17 days. And for the A(H7N9) virus, the incubation period ranges from 1 to 10 days. In the case of the swine influenza virus, the risk factor is direct or indirect contamination with infected pig or visiting locations where pigs are exhibited. The A(H5N1) infection can cause gastrointestinal disease, and symptoms include nausea, vomiting, and diarrhea. And in case of severe case symptoms reported pneumonia, septic shock, multi-organ dysfunction, hypoxemic respiratory failure, and secondary bacterial and fungal infections. Other symptoms include diarrhea, vomiting, abdominal pain, bleeding from the nose or gums, encephalitis, and chest pain, etc. If a person has pneumonia and they aren't able to breathe on their own very well, they may need to have a tube in their throat, and they may need to have artificial ventilation to support their lungs while they heal, while they recover from the infection. Vaccination is a very important tool for seasonal influenza, but there is no good vaccine for these non-seasonal influenza viruses. For a few subtypes, there are vaccines, but they're not widely available.