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Biological Warfare : Biological Terrorism : Emerging Diseases

Archived News
Week ending August 7th, 2005

Flu viruses can swap many genes rapidly to make new resistant strains, US researchers have found. Scientists previously believed that gene swapping progressed gradually from season to season. The National Institutes of Health team found instead, influenza A exchanged several genes at once, causing sudden and major changes to the virus. The findings in PLOS Biology suggest strains could vary widely each season, making it potentially harder to treat.

They also increase concerns about bird flu mutating to spread readily between humans. Each year, experts must predict which strains will be most common and design new vaccines to fight them.

Dr David Lipman and colleagues looked at strains of influenza A that had circulated between 1999 and 2004 in New York. This research confirms the genetic diversity of influenza viruses and underscores potential for reassortment These strains had given rise to the so-called Fujian strain H3N2 that caused a troublesome outbreak in the 2003-2004 flu season because the vaccine made that winter was a poor match for the virus.

Dr Lipman's team found wide variations in the 156 strains that they analysed. Some of the strains had at least four gene swaps that had occurred in a short time period. "The genetic diversity of influenza A virus is therefore not as restricted as previously suggested," said the researchers...

Investigators have determined that a strain of bird flu virus infecting fowl in Russia is the type that can infect humans, the Agriculture Ministry said Friday. The virus caused the deaths of hundreds of birds in a section of Siberia this month, but no human infections have been reported. In a brief statement, the ministry identified the virus as avian flu type A H5N1.

"That raises the need for undertaking quarantine measures of the widest scope," the statement said. Ministry officials could not immediately be reached for elaboration. Strains of bird flu have been hitting flocks throughout Asia and some fatal human cases have been reported there.

Since 2003, bird flu has killed at least 57 people in Vietnam, Thailand, Cambodia and Indonesia, which reported its first three human deaths this month. The outbreak in Russia's Novosibirsk region apparently started about two weeks ago when large numbers of chicken, geese, ducks and turkeys began dying. Officials say that all dead or infected birds were incinerated. But it is unclear whether that would effectively stop the virus from spreading.

Earlier this week, Russia's chief government epidemiologist, Gennady Onishchenko, said the virus' appearance in Russia could be due to migrating birds that rest on the Siberian region's lakes. A recent report released by the journal Science said the finding of the H5N1 infection in migrant birds at Qinghai Lake in western China "indicates that this virus has the potential to be a global threat."..

Britain is to stockpile two million doses of a bird flu vaccine in case an epidemic of the disease sweeps the globe. Manufacturers are to be invited to submit tenders for a contract to supply the H5N1 vaccine, to be used as a "first line of defence" in any outbreak, Health Secretary Patricia Hewitt said Wednesday.

` The vaccines would be used mainly to protect key medical and emergency workers. The H5N1 strain of bird flu has so far been mainly transmitted between animals, but it has also killed more than 50 people in Southeast Asia since 2003. Experts fear it could mutate into a highly infectious strain that can be easily transmitted from animals to humans or from humans to humans, unleashing a pandemic that could kill tens of millions of people.

On Wednesday, Indonesia became the latest country to confirm human deaths from bird flu. I have decided it would be prudent to purchase a limited quantity of H5N1 vaccine..

Changes in the avian flu virus have made it less deadly to ducks, potentially turning them into medical Trojan horses where the flu can hide while continuing to infect other birds and humans. Waterfowl such as ducks have been natural hosts of this type of influenza before but rarely became ill from it until 2002, when an evolving strain killed of a large number of the birds.

Since then, however, the virus has continued to change, reverting to a form less dangerous to ducks but still able to cause illness and death in chickens and humans, according to a study in Tuesday's issue of Proceedings of the National Academy of Sciences.

"These results suggest that the duck has become the Trojan horse of Asian H5N1 influenza viruses," reported a research team led by Robert G. Webster of St. Jude Children's Research Hospital in Memphis, Tenn.

"The ducks that are unaffected by these viruses continue to circulate these viruses, presenting a pandemic threat," the team said. The researchers infected domestic ducks with flu isolated at various times.

They found that ducks infected with H5N1 from 2003 or 2004 were contagious for 11-17 days, a longer transmission time than pre-2002 strains. The researchers also noted that the virus was transmitted primarily through the upper respiratory tract instead of through fecal matter as in older strains.

When flu virus from ducks that had survived the disease was administered to healthy animals, it no longer caused disease in ducks, but still caused disease in chickens. Over the last two years, hundreds of millions of birds, including poultry and wild birds, have died or were slaughtered across Asia because of the H5N1 bird flu virus...

Dating back to antiquity, influenza pandemics have posed the greatest threat of a worldwide calamity caused by infectious disease. Over the past 300 years, ten influenza pandemics have occurred among humans. The most recent came in 1957-58 and 1968-69, and although several tens of thousands of Americans died in each one, these were considered mild compared to others. The 1918-19 pandemic was not. According to recent analysis, it killed 50 to 100 million people globally. Today, with a population of 6.5 billion, more than three times that of 1918, even a "mild" pandemic could kill many millions of people.

A number of recent events and factors have significantly heightened concern that a specific near-term pandemic may be imminent. It could be caused by H5N1, the avian influenza strain currently circulating in Asia. At this juncture scientists cannot be certain. Nor can they know exactly when a pandemic will hit, or whether it will rival the experience of 1918-19 or be more muted like 1957-58 and 1968-69. The reality of a coming pandemic, however, cannot be avoided. Only its impact can be lessened. Some important preparatory efforts are under way, but much more needs to be done by institutions at many levels of society.

Of the three types of influenza virus, influenza type A infects and kills the greatest number of people each year and is the only type that causes pandemics. It originates in wild aquatic birds. The virus does not cause illness in these birds, and although it is widely transmitted among them, it does not undergo any significant genetic change.

Direct transmission from the birds to humans has not been demonstrated, but when a virus is transmitted from wild birds to domesticated birds such as chickens, it undergoes changes that allow it to infect humans, pigs, and potentially other mammals. Once in the lung cells of a mammalian host, the virus can "reassort," or mix genes, with human influenza viruses that are also present. This process can lead to an entirely new viral strain, capable of sustained human-to-human transmission. If such a virus has not circulated in humans before, the entire population will be susceptible. If the virus has not circulated in the human population for a number of years, most people will lack residual immunity from previous infection.

Once the novel strain better adapts to humans and is easily transmitted from person to person, it is capable of causing a new pandemic...

Scientists have long forecast the appearance of an influenza virus capable of infecting 40 percent of the world's human population and killing unimaginable numbers. Recently, a new strain, H5N1 avian influenza, has shown all the earmarks of becoming that disease. Until now, it has largely been confined to certain bird species, but that may be changing.

The havoc such a disease could wreak is commonly compared to the devastation of the 1918-19 Spanish flu, which killed 50 million people in 18 months. But avian flu is far more dangerous. It kills 100 percent of the domesticated chickens it infects, and among humans the disease is also lethal: as of May 1, about 109 people were known to have contracted it, and it killed 54 percent (although this statistic does not include any milder cases that may have gone unreported). Since it first appeared in southern China in 1997, the virus has mutated, becoming heartier and deadlier and killing a wider range of species. According to the March 2005 National Academy of Science's Institute of Medicine flu report, the "current ongoing epidemic of H5N1 avian influenza in Asia is unprecedented in its scale, in its spread, and in the economic losses it has caused."

In short, doom may loom. But note the "may." If the relentlessly evolving virus becomes capable of human-to-human transmission, develops a power of contagion typical of human influenzas, and maintains its extraordinary virulence, humanity could well face a pandemic unlike any ever witnessed. Or nothing at all could happen. Scientists cannot predict with certainty what this H5N1 influenza will do. Evolution does not function on a knowable timetable, and influenza is one of the sloppiest, most mutation-prone pathogens in nature's storehouse.

Such absolute uncertainty, coupled with the profound potential danger, is disturbing for those whose job it is to ensure the health of their community, their nation, and broader humanity. According to the Centers for Disease Control and Prevention (CDC), in a normal flu season about 200,000 Americans are hospitalized, 38,000 of whom die from the disease, with an overall mortality rate of .008 percent for those infected. Most of those deaths occur among people older than 65; on average, 98 of every 100,000 seniors with the flu die. Influenza costs the U.S. economy about $12 billion annually in direct medical costs and loss of productivity.

Yet this level of damage hardly approaches the catastrophe that the United States would face in a severe flu pandemic...

Monkeypox, a less deadly relative of smallpox, kills up to 10 percent of its victims in Africa. Yet a monkeypox outbreak two years ago in the United States killed no one, and scientists have wondered why.

Now they have a good idea. New research finds that there are two distinct strains of the virus, and that the U.S. outbreak involved the weaker West African one rather than the more deadly Congolese one. The illness was spread by prairie dogs after they were infected by imported African rodents at a pet distribution center.

"If it had come from Congo, we might have had a bigger problem on our hands and very well might have seen patient deaths," said Mark Buller, a St. Louis University virologist who led the federally funded study, published Friday in the journal Virology. Scientists from the U.S. Army Research Institute of Infectious Diseases, the Centers for Disease Control and Prevention, and four other universities in the United States and Canada worked on the report. The monkeypox outbreak two summers ago was the first in the Western Hemisphere. An estimated 72 people throughout the Midwest were sickened by the virus, which causes blisters and a rash that resemble smallpox...