WEDNESDAY, Feb. 17, 2005 (HealthDay News) -- Doctors in Vietnam report the troubling finding that the avian flu virus can cause potentially lethal encephalitis as well as severe respiratory infections.
Early in February 2004, two Vietnamese children -- a 9-year-old girl and her 4-year-old brother -- died of encephalitis and were later found to be infected with the virus, according to a report in the Feb. 17 issue of the New England Journal of Medicine by physicians in Ho Chi Minh City.
This is the first report indicating the virus can infect the brain. The 52 cases of human infection with avian flu virus reported by the World Health Organization in Thailand and Vietnam in 2004, 39 of which were fatal, were all characterized by respiratory illness.
"These cases suggest that the spectrum of influenza H5N1 [the formal name of the virus] is wider than previously thought," the report said.
"This is a warning to be more vigilant, but not an alarm that every case of encephalitis might be caused by the avian flu virus," said Dr. Arnold S. Monto, a professor of epidemiology at the University of Michigan School of Public Health.
But the report does add a new element of worry about a disease that has hit hard in Asia, where authorities ordered the destruction of more than 120 million poultry between January and March 2004. Worries about a possible human epidemic were heightened by a report in the Jan. 24 issue of the same journal when doctors announced that an 11-year-old Thai girl appeared to have transmitted avian flu to her mother and aunt -- the first cases of person-to-person transmission of the virus.
The new report out of Vietnam notes that avian flu infection was first suspected in the 4-year-old boy, who came to a hospital with severe diarrhea, followed by seizures, coma and death. His 9-year-old sister had died two weeks earlier with similar symptoms. Neither of the children had respiratory symptoms.
Laboratory studies found the virus in the cerebrospinal fluid, blood, throat and feces of both children, the doctors reported.
There are some worrying gaps in the report, Monto said.
"There is very little knowledge about where they got the infection," he said. "Ducks that were subclinically infected could do it. Also, there was a big gap between the time they identified the cases and the time they did the definitive virology. I would be happier in terms of the report if they were more specific about the virology."
Human influenza virus is known to cause encephalitis in some cases, said Dr. James D. Campbell, an influenza expert and an assistant professor of pediatrics at the University of Maryland School of Medicine. But encephalitis usually occurs as an aftermath to respiratory disease, he said. "What is unusual is that these cases of encephalitis occurred without respiratory symptoms," he explained.
The avian flu virus was detected only because the two cases were part of a large study looking for causes of encephalitis, Campbell said. It is possible the virus is not being identified as the cause of other cases of encephalitis because physicians are not looking for it, he said.
"If it is true that this is a common way that infection with avian influenza presents, we will have to start looking for it in other than respiratory illnesses," he said.
Campbell works in the University of Maryland's Center for Vaccine Development, which is taking part in a program to develop a vaccine against avian flu. A trial of an experimental vaccine will begin soon at Maryland and two other centers, he said.
More information
A guide to avian influenza virus is available from the U.S. Centers for Disease Control and Prevention.
