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West Nile Virus Prediction
For 2003 - A Bad Year
From Patricia Doyle, PhD
dr_p_doyle@hotmail.com
5-8-3


Hello, Jeff - Do you remember my prediction back in 1999 re availability of West Nile vaccine and a 5 year epidemiology study? Oravax co. will begin human safety trials of West Nile Virus Vaccine. (Right on schedule)
 
As for predicting that immunity will build up thus lessening the severity of West Nile Virus outbreaks, this year and subsequent years: The CDC is depending upon the manner in which West Nile Virus acted in other countries where WNV has become endemic. They have forgotten that NY99 of West Nile LIKE virus is DIFFERENT. Thus far, NY99 West Nile LIKE virus has acted far differently in the US, Canada, and I suspect Central and South America, than it has in other areas of the world. I doubt that there will be enough immunity build up in the forseeable future to ensure mitigation of the virus outbreaks.
 
I think that 2003 is going to be a very virulent year for West Nile LIKE virus in the entire Western Hemisphere.
 
Patricia Doyle
 
[1] Summary from Nature (May 8, 2003): "US Fails to Quantify Threat
of West Nile Virus"
[2] Levitan comment re: immunity as barrier to outbreak
[3] Full text of Nature article "US Fails to Quantify Threat of West
Nile Virus"
 
[1]
US FAILS TO QUANTIFY THREAT
OF WEST NILE VIRUS
Byline: Hannah Hoag
Nature 423, 104 (May 8 2003)
 
Summary:"despite a [US] national effort involving several federal agencies, including a $40-million investment in research and surveillance by the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, officials still have no reliable estimate of the likely scale of this year's outbreak. Since it was detected in New York state in 1999, the virus has surged westwards. Last year it infected at least 4,000 people in the United States, killing 284, and public-health officials are predicting that the virus will spread to cover the whole country this year.
 
But virologists also expect both humans and animal host populations in the United States to begin developing immunity to the virus, as has happened in other parts of the world where the virus is already endemic. However, there is so far no reliable estimate of how long this immunity will take to build up, leaving researchers unsure of the likely death toll for this year."
 
[2]
I question whether post-exposure immunity would be a significant factor in limiting WNV case numbers this year or in the near future if CDC's rule-of-thumb ratio relating serious WNV-associated illness with exposure is still considered close to the mark.
 
I.e., If it is still thought that 1 in 150 human infections with WNV leads to serious illness, then one might expect that many fewer than one million people in the US have been exposed to WNV infection, and therefore have acquired immunity.
 
This estimate that 750,000 people may have been exposued to WNV since 1999 was calculated by multiplying 150 x 5,000. The number 5,000 is a generous estimate of the number of human cases of serious WNV-associated illness in the US since 1999. Is this logic correct?
 
Lois Levitan, PhD
Environmental Risk Analysis Program
Cornell University
Ithaca, New York USA 14853-5601
Email: LCL3@cornell.edu
 
 
[3]
Nature 423, 104 (May 8 2003) [Full text]
 
 
US FAILS TO QUANTIFY
THREAT OF WEST NILE VIRUS
Byline: Hannah Hoag
 
[WASHINGTON] Public-health authorities in North America are gearing up for the return and probable spread of West Nile virus, which last year claimed the lives of more than 200 people.
 
But despite a national effort involving several federal agencies, including a $40-million investment in research and surveillance by the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, officials still have no reliable estimate of the likely scale of this year's outbreak.
 
West Nile virus is carried by birds and is mainly spread to humans by mosquitoes. It is a member of the flavivirus family, which includes yellow fever and St Louis encephalitis, but in humans it is not usually life-threatening, although in about 1% of cases it causes severe meningitis and encephalitis.
 
Since it was detected in New York state in 1999, the virus has surged westwards. Last year it infected at least 4,000 people in the United States, killing 284, and public-health officials are predicting that the virus will spread to cover the whole country this year.
 
But virologists also expect both humans and animal host populations in the United States to begin developing immunity to the virus, as has happened in other parts of the world where the virus is already endemic. However, there is so far no reliable estimate of how long this immunity will take to build up, leaving researchers unsure of the likely death toll for this year.
 
"We should be prepared for an outbreak just as large, if not larger than last year's," says Lyle Petersen, of the CDC's division for vector-borne diseases. "There is nothing to prevent it from happening again."
 
US researchers have identified 36 species of mosquito that can carry and transmit the virus to humans, although three species of Culex mosquito seem to be responsible for most US cases.
 
Last year, 21 people were infected through blood transfusions, and four became infected after receiving organ transplants from infected donors. Two companies are developing screening tests in an effort to prevent further human-to-human transmission of the virus. The tests are expected to be ready by 1 July.
 
But experts are criticizing the US response to the virus, describing current efforts as patchy. Because of funding cuts, some state health departments have dispensed with bird surveillance programmes, which track and identify the incidence of the virus in birds, on the premise that the virus has already become endemic.
 
In California, where the virus has yet to arrive and where the relatively high number of outdoor workers, such as farm labourers, could heighten health risks, officials are preparing for the worst. "We fully expect that West Nile virus will be introduced and become established this summer," says Vicki Kramer, chief of the vector-borne disease section of the state's health department. California has established a network of 200 chicken flocks which will be monitored by health officials for the arrival of the virus.
 
University researchers and biotechnology companies, meanwhile, are trying to develop a vaccine. Drug firm Acambis in Cambridge, Massachusetts, for example, this summer plans to begin human safety trials of a live vaccine, based on an established vaccine against yellow fever. A DNA vaccine - derived from the virus's RNA - and one derived from its protein coat are also being developed.
 
Other researchers are looking at how to improve control of the mosquitoes. Researchers at the US Agricultural Research Service in Gainesville, Florida, have identified a baculovirus that selectively infects and kills the Culex mosquito. But the team has yet to find a commercial partner to develop the idea into an insecticide that could be approved and used.
____
 
Patricia A. Doyle, PhD
Please visit my "Emerging Diseases" message board at:
http://www.clickitnews.com/emergingdiseases/index.shtml
Zhan le Devlesa tai sastimasa
Go with God and in Good Health

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