Indian scientists warn of "Mutant Measles" Virus

Ganapati Mudur / British Medical Journal BMJ 2001;322:693 24mar01

Indian scientists have warned that India may be witnessing the emergence of a highly lethal measles-like virus, causing encephalitis in adults and children.

Scientists investigating an outbreak of encephalitis among adults in the town of Siliguri, in West Bengal, told the health ministry this week that the disease was caused by a mutant measles virus that affects the brain, lungs, or kidneys.

"For now, we're calling this a variant of measles," Dr Nirmal Kumar Ganguly, director general of the Indian Council of Medical Research, told the BMJ.

This is India's third outbreak since 1998 of a highly fatal illness involving the brain or the kidneys and attributed to the measles virus. The unexplained outbreak in February this year killed at least 28 people, including two doctors and five nurses in a clinic. The infection spread through droplets in air expelled by patients during the terminal phase of the illness, which is marked by pneumonia.

Epidemiologists say that adequate protection and barrier nursing helped to quell the outbreak. Investigations had ruled out vector borne infections common in India, such as cerebral malaria or Japanese encephalitis. Tissue samples studied at the National Institute of Virology in Pune showed antibody signatures of measles in 17 samples collected. Measles virus antigen was detected in brain tissues of two patients. The diagnosis has also been confirmed through other tests for the virus.

"A measles-like virus that is highly fatal to adults and spreads through droplets in the air is very worrying," said Dr T Jacob John, a leading Indian virologist, formerly with the Christian Medical College in Vellore. "This doesn't look like a one-time event. India may even have had early warnings."

Two years ago a team from the National Institute of Virology had isolated the measles virus from five adults in Bombay with acute renal failure and neurological symptoms. Four of the patients died, but none had a rash. The institute had also isolated the measles virus in two highly fatal outbreaks of encephalitis among children aged under 12 years in three states Haryana, Gujarat, and Andhra Pradesh during 1998.

"In those previous outbreaks, immunisation seems to have failed to protect against this virus," said Dr Ganguly.

The National Institute of Virology had said last year that the absence of a rash and unusual symptoms may mean that measles was re-emerging in India despite widespread vaccination coverage. Virologists say that genetic studies of the virus are necessary.