Despite rising concerns of an avian flu outbreak among birds in the UK, experts say that the threat of infection among humans is low. Avian flu caused by influenza A virus also called bird flu is usually seen in poultry farms.
Although there have been multiple reports of various strains of bird flu worldwide, the most recent strain that has been causing a rampant outbreak among the poultry population is the influenza A H5N1 strain. In May 2023, WHO (World Health Organization) reported that Europe is currently experiencing a H5N1 virus epidemic in domestic and wild birds and mammals in 24 countries. In India, it was reported in the states of Kerala, Jharkhand and Maharashtra.
Additionally, WHO reported one confirmed human infection caused by avian influenza A (H5N1) in Chile on 6th April 2023.
Birds of all kinds, including chickens and wild birds like ducks, are susceptible to avian flu viruses, says Dr Kirti Sabnis, infectious diseases specialist, Fortis Hospital, Mumbai.
Influenza A virus can infect domestic poultry, various bird and animal species, as well as wild aquatic birds. However, it is uncommon for birds to infect humans.
Widespread reports of avian flu
“It is not the first time that avian flu has infected humans. Multiple avian flu strains have jumped the species barrier to infect humans since the year 2003. The first case of avian flu infection (H5N1) in humans was reported in 2003 in China. Since then several hundred cases have been reported in humans,” says Dr Aniket Sanyal, director, ICAR- National Institute of High Security Animal Diseases, Bhopal, Madhya Pradesh.
How does avian flu spread
The virus circulates among poultry birds, says Dr Netto George Mundadan, assistant professor, department of infectious diseases, GMC Kottayam, Kerala. “The common influenza subtypes seen in poultries are H5N1, H9N2, H4N6 and H7N7,” he said. These mutant strains are carried by migratory birds, which tend to stay in an area for a few months. They pass them on to poultry birds and then on to humans through consumption.
He mentions that avian flu is a high pathogenicity strain. “Pathogenicity refers to the ability of the viral strain to cause infection. Thus, viruses like H5N1 have high pathogenicity especially when the poultry animals are culled,” he explained.
Can humans get avian flu
Most people who get bird flu have had close contact with infected birds or with surfaces that have been contaminated by the birds’ saliva, mucus or droppings. “It is also possible that some people may get infected after swimming or bathing in water contaminated with the droppings of infected birds,” says Sabnis.
Human-to-human transmission is rare and usually occurs in close, prolonged contact of those infected, such as family members or healthcare workers, says Dr Sanyal.
Avian flu symptoms
Avian flu cannot be diagnosed by clinical signs alone and lab tests are a must. Symptoms in humans are similar to flu and some can remain asymptomatic too.
Dr Sanyal lists out typical symptoms of bird flu in humans:
- Fever
- Cough
- Sore throat
- Runny or stuffy nose
- Breathlessness
- Pneumonia (severe cases)
The high-risk groups according to Dr Mundadan are those with low immunity, chronic disease, pregnant women and new-borns.
How to distinguish between avian flu and seasonal flu
There are some differences that can help distinguish avian flu from seasonal flu, explains Dr Sanyal.
- Onset and duration: The symptoms may appear within a few days of exposure to the virus. The duration of illness can vary but is generally longer compared to seasonal flu, with a more prolonged recovery period.
- Respiratory symptoms: Avian flu infections, particularly with H5N1 and H7N9, can cause severe respiratory symptoms. These may include cough, sore throat, difficulty breathing and chest congestion. They could become life-threatening.
- Gastrointestinal symptoms: Unlike seasonal flu, some strains of avian flu can cause gastrointestinal symptoms such as diarrhea, abdominal pain and vomiting. These symptoms can be more prominent in the H5N1 strain.
How to prevent avian flu spread in humans
If avian flu is detected, swift action must be taken to quarantine infected or at-risk birds. “The best way to mitigate the spread of avian influenza to humans is by using appropriate PPE (Personal Protective Equipment) and following biosafety protocols during high-risk activities such as sampling of infected birds, culling and disposing of infected birds/animals,” explains Dr Sanyal.
All persons involved in these tasks should be registered and monitored closely by local health authorities for at least seven days following the last day of contact with infected animals or their environments, he adds. There must be robust surveillance systems to monitor and detect avian flu cases in both birds and humans.
Precautions to prevent bird flu in humans
- Annual influenza vaccine – Even though there is no vaccine for humans for bird flu yet, people can take the annual influenza vaccine that can provide 50% to 70% protection from the virus.
- Sanitization protocols – Wearing masks, avoiding crowds, maintaining personal hygiene etc.
- Ensure that all poultry products, including eggs and meat, are cooked thoroughly at an appropriate temperature.
Takeaways
- Avian flu virus infection is seen predominantly in domestic poultry and sometimes in wild aquatic birds.
- In 2023, Europe’s poultry population was affected by a rampant H5N1 outbreak, while Chile recently confirmed a case of bird flu in a human caused by the H5N1 variant.
- Humans can contract the flu if they come in close contact with infected birds or with surfaces or water contaminated by the birds’ saliva, mucus or droppings.
