- 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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