New Delhi, July 8: India is among the winter destinations of migratory birds infected with the deadly avian influenza virus around a lake in China, scientists reported today.
The virus, H5N1, which can spread from birds to humans, has killed 54 people in Southeast Asia over the past year. “The virus has the potential to be a global threat,” George Gao at the Chinese Academy of Sciences and his colleagues said in their report.
Over the past two months, scientists have detected more than a thousand sick or dying birds infected with the virus around Quinghaihu lake in central China.
Their studies, published this week in research journals Science and Nature, have raised concerns that migratory birds may help H5N1 spread across Asia and beyond.
“This lake is one of the most important breeding locations for migratory birds that overwinter (spend winter) in Southeast Asia, Tibet and India,” Gao and his colleagues wrote.
The infected birds include bar-headed geese, great black-headed gulls and brown-headed gulls.
While acknowledging the potential threat from migratory birds, independent scientists said it is not known yet whether infected birds can last the journey through mountain passes in the Himalayas.
“All three species visit India during winter,” said Dr Taej Mundkur, a waterbird ecologist who has been tracking bird migration in Asia. “An individual bar-headed goose tagged at Quinghaihu was once tracked all the way into Karnataka,” Mundkur told The Telegraph.
Scientists say the black-headed and brown-headed gulls are found across India, but there is no evidence to show they travel from Quinghaihu. These gulls also nest in high-altitude lakes in Ladakh.
Over the past year, Indian government scientists have screened more than 12,000 blood samples from poultry, pigeons, pigs and at least 120 wild birds.
“There is no sign of H5N1 in India yet,” said Dr Hare Krishna Pradhan, director of the High Security Animal Disease Laboratory in Bhopal.
The Chinese microbiologists extracted H5N1 from the brains and throats of the sick birds at Quinghaihu with symptoms of diarrhoea and neurological disorders. In tests to evaluate its virulence, they found that the virus killed all eight chickens and eight mice deliberately infected with it.
Experts on infectious diseases believe an influenza pandemic (an epidemic affecting a vast area) is “inevitable and imminent”. During the 20th century, the world witnessed three global epidemics of influenza. The worst of them in 1918-19 killed more than 40 million people.
Scientists fear H5N1 may exchange genes with human viruses, gain the ability to move from person to person through coughs and sneezes, and trigger the next influenza pandemic.
Most human cases of H5N1 so far have involved people who have had contact with live, diseased poultry. Infected birds secrete large amounts of virus in their droppings, contaminating dust and soil around them.
Since January 2004, unprecedented outbreaks of H5N1 in poultry and humans across South-east Asia have alarmed scientists. Millions of chickens have been affected in Cambodia, China, Indonesia, Japan, Korea, Laos, Thailand and Vietnam.
The virus has also killed 54 among 108 people infected in Vietnam, Thailand and Cambodia over the past year, the World Health Organisation said last week.
But scientists say it takes geese several weeks to fly from China to India. “It’s a stressful flight and we don’t know whether an infected bird would survive it,” Mundkur said.
Ecologists have urged studies to map distributions of these migratory birds in India and examine whether they intermingle with local birds.
The first human outbreak of H5N1 occurred in Hong Kong in 1997, when the virus killed six people. Health authorities averted a pandemic by ordering mass slaughter of 1.5 million poultry.