People are told to take precautions while handling poultry products or unpasteurised milk
Hyderabad: With the avian flu (Influenza A H5N1) spreading among dairy animals and poultry, there is an emerging concern about whether the disease can also spread to humans.
Although direct human infections with 'highly pathogenic Avian influenza’ HPAI A(H5N1) virus are rare, unprotected exposure to infected animals or contaminated environments significantly increases the risk of infection. Individuals with direct or prolonged contact with infected birds or their environments are at heightened risk.
As of now, there is no evidence of human-to-human transmission. Cases reported globally have been limited to animal-to-human or bird-to-human transmission (besides being panzootic). The United States has reported 68 human cases so far, including one fatal.
However, if humans catch the virus, the fatality rate is more than 50 per cent. As per the recent World Health Organisation (WHO) update, there have been 954 cases of human infection with the avian influenza A (H5N1) virus reported from January 1, 2003, to December 12, 2024, from 24 countries. Of these 954 cases, 464 were fatal (cumulative fatality rate of 49 per cent).
"With a mortality rate exceeding 50 per cent, the seriousness of this virus cannot be understated," said Dr Vyakarnam Nageshwar, pulmonologist and president of the World Allergy Foundation.
The concern revolves around the H5N1 strain of H5 viruses, classified as 'highly pathogenic Avian influenza' (HPAI), which is caused by specific influenza A virus strains belonging to the H5 and H7 subtypes.
Typically, HPAI viruses are absent in wild birds. However, when a low-pathogenic H5 or H7 strain infects poultry, it can evolve into a highly pathogenic strain. Before 1997, it was believed that HPAI viruses could not infect or cause severe illness in humans. This assumption changed after several severe human cases of H5N1 infections were diagnosed in the recent past.
According to a study published in ‘Science’ journal in December, the virus is just one mutation away from becoming transmissible between humans.
Despite the continuous circulation of H5N1 viruses in poultry, only a limited number of human infections have been recorded. Severe human infections are typically linked to high levels of exposure to the virus, leading to complications such as viral pneumonia, acute respiratory distress syndrome, and multi-organ dysfunction. Diarrhoea is also common during human H5N1 infections.
Avian influenza A viruses infect the respiratory and gastrointestinal tracts of birds, causing them to shed the virus in their saliva, mucus, and faeces. In humans, infections can occur if the virus enters through the eyes, nose, or mouth, or is inhaled.
People in close, unprotected contact with infected birds or contaminated environments are at greater risk. Illnesses can range from mild symptoms such as those exhibited in upper respiratory infections, conjunctivitis and severe conditions like those in pneumonia, multi-organ failure, sometimes resulting in death.
"This virus behaves like any other virus and can be treated with antiviral medication. Common symptoms include fever, body aches, neck pain, headaches, and joint pain. However, what distinguishes this virus is its tendency to spread through conjunctival fluids. Touching your eyes after contacting an infected surface accelerates transmission. If untreated, viral conjunctivitis can lead to conjunctival haemorrhage," Dr Vyakarnam explained.
The Telangana government had released an advisory for citizens to stay alert in June as the virus was spreading among birds and poultry in the neighbouring states.
Doctors have called for greater protection of dairy farm and poultry farm workers, as well as regulation of how meat and eggs are handled at meat shops as the virus can be an occupational risk for now.
“Dairy and poultry farm workers need to wear protective gear while handling animals and dairy products. The raw and unpasteurised milk and eggs can transmit the virus to humans and other animals on the farm. Workers can carry the virus and infect other animals. The eggs should be placed in separate containers. Even if someone is boiling eggs, they need to ensure that egg shells are disposed of properly and eggs are used only in high-temperature cooking," said Dr T.M.J. Rajesh, consultant internal medicine.
"Those handling meat also need to ensure that each time a bird is handled, the utensils are sanitised and meat is kept in separate containers. They need to wear protective gear as well," he added.
