Human deaths from bird flu raise fear of global outbreak

GENEVA, Switzerland, January 26, 2004 (ENS): World Health Organization officials are concerned that a strain of avian influenza now spreading across Asia might exchange genes with a human virus to create a new virus that could spread easily among people. Over the past month, millions of chickens in seven countries have either died or been destroyed because of the highly infectious bird flu strain, known as H5N1.

While the World Health Organization (WHO) says that at present it has no evidence that person-to-person transmission is occurring, seven human cases in Viet Nam and two in Thailand within the past month coincide with an historically unprecedented spread of H5N1 bird flu in the poultry populations of Asian countries.

Since mid-December 2003, outbreaks of H5N1 disease in poultry have been confirmed in Cambodia, Japan, Laos, South Korea, Thailand, and Viet Nam. (Editor's Note: It is now being reported that China has also developed cases of the disease*).

In addition, Indonesia's agriculture minister confirmed Sunday that 4.7 million chickens had died of disease since November. About 40 percent were stricken with avian flu, while the remaining 60 percent died from Newcastle disease, which is harmless to humans.

Bird flu also was reported on a farm in Taiwan this month, but turned out to be a different strain.

Today, Viet Nam and Thailand are the only two countries in which human cases of H5N1 avian influenza are known to have occurred in the current outbreak, WHO says.

The Ministry of Public Health in Thailand Friday informed World Health Organization officials of two cases of H5N1 avian influenza in humans. Both cases, which are in two boys, are laboratory confirmed, and one boy has now died (Editor's note: The second boy has also been reported dead. Thailand confirmed its second causality to the bird flu Tuesday*.) More patients with respiratory symptoms that might indicate the H5N1 infection are being tested, and results are expected this week.

Lab tests Friday confirmed two additional human cases of H5N1 avian influenza in Viet Nam, the first to be confirmed in the south of the country. The cases, both in Ho Chi Minh City, are two children, an eight year old girl and a 13 year old boy. The boy died on January 22, WHO reports. The girl is hospitalized in stable, but critical condition.

They bring the total number of confirmed H5N1 cases in Viet Nam to seven, including five in Hanoi. Of the seven cases in Viet Nam, six people have died since December 30, 2003.

Laboratories in the WHO Global Influenza Surveillance Network are characterizing avian and human viruses obtained from the current outbreaks, and the agency reports that the genome of the H5N1 bird flu strain has now been sequenced.

All genes are of avian origin, indicating that the virus that caused the deaths had not yet acquired human genes. The acquisition of human genes increases the likelihood that a virus of bird origin can be transmitted from one person to another.

Preliminary lab results indicate that these viruses are different from other H5N1 strains isolated in Asia in the recent past, so WHO says it will be necessary to develop a new prototype strain to manufacture a vaccine capable of fighting the current outbreak.

The virus reservoir is wild birds and there is no method available to control it, health officials say.

An international team led by WHO scientists is in Viet Nam working with health authorities to assess the current situation, conduct epidemiological investigations, and identify the most appropriate control measures.

In Viet Nam, H5N1 infection in poultry has now been detected in 23 of the country’s 61 provinces. Since 23 December 2003, about 2.9 million poultry stock have either died or been destroyed because of the disease.

In Thailand, the number of birds dead or killed by agricultural workers and soldiers in 24 provinces has reached 9.1 million. Sunday, China and Burma joined a growing number of countries which have banned imports of Thai chicken.

In response to claims that the government tried to cover up the presence of bird flu, Ampon Kitti-ampon, director of the National Bureau of Agriculture Commodities and Food Standards, told the "Bangkok Post" that the virus might have been in Thailand for some time, but has gone undetected due to "technical errors'' in ministry sampling and testing processes.

WHO scientists will be collaborating with health authorities in Thailand in responding to the situation there.

WHO has identified the rapid culling of H5N1 infected or exposed poultry as the most important line of defense for preventing further human cases and possibly averting the emergence of a new influenza virus capable of causing an influenza pandemic.

A pandemic is a global outbreak of flu and occurs when a new influenza virus emerges, spreads, and causes disease worldwide. Once a new pandemic influenza virus emerges and spreads, it typically becomes established among people and circulates for years. Past influenza pandemics have led to high levels of illness, death, social disruption and economic loss.

In 1918 and 1919, the so-called Spanish flu, strain H1N1, caused the highest number of known flu deaths. More than 500,000 people died in the United States, and 20 million to 50 million people may have died worldwide, according to the U.S. federal Centers for Disease Control.

The first recorded outbreak of H5N1 infection in humans occurred in Hong Kong in 1997, when 18 persons developed serious disease and six died. Investigations of the Hong Kong outbreak determined that close contact with live infected poultry was the source of human infection in all 18 cases.

For this reason, WHO recommends that the practice of marketing live poultry directly to consumers should be discouraged in areas now experiencing outbreaks of H5N1 avian influenza among poultry.

While trade restrictions have been put in place by some countries to protect animal health, on the basis of presently available data, WHO does not conclude that any processed poultry products - whole refrigerated or frozen carcasses and products derived from them - and eggs in or arriving from areas currently experiencing outbreaks of avian influenza H5N1 in poultry flocks pose a risk to public health.

Influenza viruses are killed by adequate heat, the international health agency says, emphasizing the importance of good hygiene practices during handling of poultry products, including hand washing, prevention of cross-contamination, and thorough cooking.

At this time WHO has not issued any travel alerts or advisories for the region in response to the H5N1 outbreak. But travelers to countries in Asia with documented H5N1 outbreaks are advised to avoid poultry farms, contact with animals in live food markets and any surfaces that appear to be contaminated with feces from poultry or other animals.

The Centers for Disease Control warns U.S. residents that in Vietnam and in other tropical regions, influenza can occur at any time during the year. People at risk of developing influenza related complications and healthy people who want to decrease their risk of catching bird flu should receive the 2003-04 trivalent influenza vaccine. The vaccine is believed to protect against three viruses and offers some protection against variants of them as well.

But if an H5N1 epidemic does take off globally, researchers at St. Jude Children’s Research Hospital say the United States is not prepared to respond rapidly. This finding, reported in the November 28, 2003 issue of the journal "Science," is co-authored by said Robert G. Webster, Ph.D., a member of the Infectious Diseases department at St. Jude's.

“If an influenza pandemic started tomorrow, we would not be able to head it off with vaccines because the production facilities available to produce them are grossly inadequate,” said Webster.

In addition to the limited ability to respond to an outbreak with vaccines, the supply of antiviral drugs that might slow a pandemic is in “scandalously short supply,” the St. Jude study states.

“In the face of a pandemic, the available supplies of antiviral drugs would be used up in days,” Webster said. “It would take up to 18 months to make more drugs from scratch. Stockpiling is the only answer.”

The St. Jude investigators warn that while vaccine production technology in the United States is adequate, needed legislative and infrastructure changes have not been made. They say intellectual property laws that limit or slow the incorporation of new knowledge into vaccine production are part of the problem.

Webster's team says a factor driving the evolution of flu viruses is the ongoing mixing of human and lower-animal influenza virus genes inside infected birds and swine kept in close quarters in markets or farms. The animals serve as “mixing bowls” in which influenza viruses swap genes, Webster warns, increasing the chance that some viruses will obtain the ability to spread rapidly among infected humans.

Copyright Environment News Service (ENS) 2004. All Rights Reserved.


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