Explainer: What is Bird Flu; Can it Threaten Humans?

India has reported fresh cases of bird flu infection in at least four different states. The current infections in India were due to the H5N8 strain of the bird flu virus and the National Institute of High Security Animal Diseases(NIHSAD) of the ICAR (Indian Council of Agriculture Research) has confirmed the same.

All the states which have reported such cases recorded deaths of migratory birds, crows and poultry. Kerala has ordered for the culling of poultry after an outbreak of bird flu among ducks; about 21,000 instances of culling have already been reported after Himachal Pradesh witnessed the deaths of nearly 2,000 birds.

Reports of an outbreak have resulted in widespread fear among common people and those associated with poultry farms. India has witnessed several spells of bird flu since 2006 which have caused severe losses to poultry farmers.

What is Bird Flu?

Bird flu or avian influenza is a viral disease. The disease primarily affects poultry like chickens, ducks or turkeys. There are many strains of the virus with some causing mild symptoms in birds and others having a more lethal effect.

Influenza A viruses occur naturally in the wild, especially in aquatic birds like ducks and geese. These species can act as natural reservoirs of the virus. Many birds carry the virus without having any symptoms and shed it via their droppings.

Which States Have Been Affected in India?:

Four states in India have reported cases of bird flu including Rajasthan, Madhya Pradesh, Himachal Pradesh and Kerala. Rajasthan has mainly detected cases in crows and it has been reported that 16 out of 33 districts in the state recorded bird fatalities.

Bird flu was reported to be the cause of mass deaths of crows in Madhya Pradesh. The districts of Mandsaur, Indore and Agar Malwa have been affected with a total of around 400 avian deaths reported from ten districts in the state.

The state of Himachal Pradesh recorded bird flu-related deaths among migratory birds, especially in bar-headed geese. Thousands of such were found dead in the Pong Dam lake in Kangra district.

The districts of Kottayam and Alappuzha in Kerala recorded deaths of about 1,700 ducks. The state authorities have ordered culling of domestic poultry.

Can it Threaten Humans?

The avian influenza virus does not spread to humans easily. Among a dozen existing strains of the virus, the two that have infected humans in recent times are H5N1 and H7N9. Generally, the virus is transmitted to humans who come in close contact with infected birds. According to the WHO advisory: “Human infections are primarily acquired through direct contact with infected animals or contaminated environments, these viruses have not acquired the ability of sustained transmission among humans.”

However, in a few cases, the virus has been reported to have been transmitted from one human to another. However, only sporadic cases have been reported since 2015. Primary precautionary measures are for those working in poultry farms and those having a chance of exposure to infected birds.

When bird flu infects humans, it can turn out to be deadly. It is found that “the virus infections in humans may cause disease ranging from mild upper respiratory tract infection (fever and cough), early sputum production and rapid progression to severe pneumonia, sepsis with shock, acute respiratory distress syndrome and even death. Conjunctivitis, gastrointestinal symptoms, encephalitis and encephalopathy have also been reported to varying degrees depending on subtype”.

In cases of infection by the H5N1 strain, six out of 10 cases of infected humans resulted in death.