Bird flu has been reported among wild geese in Himachal Pradesh, crows in Rajasthan and Madhya Pradesh and ducks in Kerala. In Haryana, around one lakh poultry birds have died mysteriously in the last few days.
In Himachal Pradesh’s Pong Dam Lake, around 1,800 migratory birds have been found dead. In Kerala, the flu has been detected in two districts, prompting authorities to order culling of ducks. A bird flu alert has been sounded in Rajasthan, where over 250 crows were found dead in half a dozen districts.
What is avian influenza?
It is a highly contagious viral disease caused by Influenza Type A viruses which generally affects poultry birds such as chickens and turkeys. There are many strains of the virus – some of them are mild and may merely cause a low egg production or other mild symptoms among chickens, while others are severe and lethal.
How does the bird flu spread?
Wild aquatic birds such as ducks and geese are the natural reservoir of Influenza A viruses and the central players in the ecology of these viruses.
Many birds carry the flu without developing sickness, and shed it in their droppings. Since birds excrete even while flying, they provide “a nice aerosol of influenza virus, shedding it all over the world”, in the words of American virology professor Vincent Racaniello.
From water birds, many of whom migrate and travel long distances, the viruses are thus further spread to poultry and terrestrial birds. Sometimes, the virus jumps over to mammals such as pigs, horses, cats and dogs.
When and how did the bird flu start infecting humans?
Bird flu outbreaks have been affecting poultry around the globe for decades, and culling of infected birds has been a common measure to contain the spread. But it was in 1997 when humans are first known to have contracted bird flu following an outbreak in a live bird market of Hong Kong. It was the H5N1 strain of the virus, and 6 out of 18 infected humans died of the disease.
It was contained, but re-emerged a few years later in various other parts of the globe and caused hundreds of human deaths, particularly in Southeast Asia. Movement of infected poultry and migratory birds, and an illegal bird trade are believed to be the causes of the spread. Some mammals such as cats and lions were also infected.
Subsequently, several other strains of the virus such as H5N2 and H5N8 jumped from animals to humans, thus becoming a global public health concern.
Does it spread easily to humans?
No, it does not. Generally, people coming in close contact with infected alive or dead birds have contracted the H5N1 bird flu, and it does not usually spread from person to person, as per the WHO. There is also no evidence, the WHO says, that the disease can be spread to people through properly prepared and cooked poultry food. The virus is sensitive to heat, and dies in cooking temperatures.
Then why the scare?
H5N1 is severe and deadly – around 6 out of 10 confirmed cases in humans have led to deaths (though the actual mortality rate may be lower due to under-reporting of asymptomatic cases).
If the virus mutates and becomes easily transmissible from person to person, say by altering its shape to grab human cells much more effectively, it can potentially cause a pandemic.
Also, flu viruses are more prone to mutation because they have a segmented genome. All known strains of flu – including the seasonal flu and the pandemic flu – have jumped from birds to humans in this way.
Bird flu in India
In India, no case of bird flu in humans has been detected so far, according to the Union health ministry. The department of animal husbandry has reported 25 episodes of H5N1 bird flu in poultry in 15 states from 2006 (when the first outbreak occurred in Maharashtra and Gujarat) till 2015. It has also been detected in crows.
What are its symptoms and treatment?
Unlike in birds, where it generally infects the gut, the avian influenza attacks the respiratory tract of humans and may cause severe respiratory illnesses such as pneumonia or Acute Respiratory Distress Syndrome (ARDS). Its early symptoms include fever, cough, sore throat, and sometimes abdominal pain and diarrhoea.
Antiviral drugs, especially oseltamivir, improve the prospects of survival in humans, according to the Union health ministry. The ministry advises people working with poultry to use PPEs and follow hand hygiene. In the US, the FDA approved a vaccine for the H5N1 virus in 2007.
Among poultry birds, vaccination strategies advised by the World Organisation for Animal Health can be used to prevent the flu, and the Organisation recommends eradicating the highly pathogenic avian influenza (HPAI) at its source to decrease the disease in avian species and further human infections.