Bird Flu Cases Increase

Bird Flu Cases Increase, Adding Credence to Warnings, Computer models aid in containment strategies if human pandemic erupts, By Charlene Porter, Washington File Staff Writer. Washington – The steady creep of a deadly form of avian influenza, or bird flu, lends further credence to warnings issued by international health officials for months that the H5N1 virus could trigger a worldwide flu pandemic.

Vietnam remains the nation most seriously affected with the appearance of bird flu in humans; officials there report, and the World Health Organization (WHO) confirms, three additional cases of human infection with the virus that has caused the deaths of hundreds of millions of poultry across Asia.

Vietnam has detected a total of 90 human cases of H5N1 since the disease first began to appear in the region in late 2003. Of those, 40 have died.

WHO’s official accounting of human cases issued August 5 tallies 112 in four nations – Vietnam, Thailand, Cambodia and Indonesia. After Vietnam, Thailand has confirmed the most avian influenza cases – 17 – while Indonesia is the most recent government to report a human death. A man who died July 12 had two young daughters who also became ill and subsequently died. Tests are still ongoing to determine whether H5N1 was the cause of the girls’ deaths.

As the human toll of the disease increases, so does the spread of the virus among bird populations. Russian animal health officials have reported to the World Organisation for Animal Health the appearance of H5N1 in three villages in Novosibirsk province.

This Russian region borders on Kazakhstan, where a strain of bird flu is also reported, according to news reports, but not yet confirmed as the highly dangerous H5N1 strain.

This strain infected humans for the first time in only 1997, health officials say, so immunity to it is virtually nonexistent in people. The pattern of human infection so far proves that the virus is not easily transmitted between humans. Most cases have been traced to close contact with infected birds.

Health authorities fear though that H5N1 will mutate to become more transmissible between humans. If that happens, in a world of rapid transit and globalized travel, experts say a flu pandemic could sweep from nation to nation with the potential death toll in the tens of millions, and economic and trade disruption of immense proportions.

Pandemic Research

A timely response with a targeted distribution of antiviral drugs could contain an epidemic and prevent a global spread, according to research published by international research teams. Using computer models, the research shows that pandemic could be prevented with a combination of carefully implemented public health measures introduced soon after the first cases appear.

Scientists in the United States, Hong Kong, Thailand and France produced the work as participants in a research network funded by the National Institute of General Medical Sciences (NIGMS), a component of the National Institutes of Health.

Two different computer models tested different outbreak scenarios, according to an August 3 NIGMS press release. One focused on 85 million people in Thailand and bordering regions of neighboring countries. Published in the magazine Nature, this study found that 3 million courses of antiviral drugs targeted for treatment of infected individuals and all their contacts – family, friends, schoolmates, coworkers, and shopkeepers – could have more than a 90 percent chance of stopping the virus.

A second computer model developed a scenario involving 500,000 people in rural Southeast Asia. Described in the magazine Science, this model applied similar treatment and response strategies to those of the first study, but also called for the pre-pandemic inoculation of the population with a flu vaccine, even though the vaccine would be considered low-efficacy. That is, it would be a vaccine of limited value because it would not have been specifically developed to target a rapidly emerging, previously unknown viral strain.

An inoculation campaign would help bolster the effectiveness of the other containment strategies such as quarantine and antiviral treatment according to the study. Under that scenario, the spread of the pandemic might be contained to less than one case per 1,000 people.

Further information on both studies is available at the MIDAS (Models of Infectious Disease Agent Study) Web site.

more at avian influenza or bird flu and H5N1 or pandemic and World Health Organization or National Institutes of Health