WNV Activity Update (Aug 26, 2004)

[1] United States: CDC MMWR: WNV Activity, Aug 18-24, 2004 + Cumulative
[2] Canada: Health Canada Surveillance Data
[3] Canada: Details from
[4] Arizona, US Epicenter of 2004 WNV Outbreak -- Why?

[1]
UNITED STATES: CDC MMWR, WNV ACTIVITY AUGUST 18-24, 2004 + CUMULATIVE
Source: Centers for Disease Control and Prevention (CDC) MMWR August
27, 2004 / 53(33);770-771 [edited]
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5333a6.htm>

August 18-24 154 cases of human WNV illness were reported from 18
states (Alabama, Arizona, California, Colorado, Connecticut, Florida,
Georgia, Illinois, Kentucky, Minnesota, Mississippi, Missouri, Nevada,
New Mexico, North Carolina, South Dakota, Tennessee, and Wisconsin).

During 2004, 32 states [across the continental US] have reported 843
cases of human WNV illness [20 fatalities] to CDC through ArboNET [see
online map for details]. Of these, 304 (36%) cases were reported from
Arizona; [234 from California; 141 from Colorado; 27 from New Mexico
and fewer than 20 in other states]. [Of the 843, 307 showed symptoms
of neuroinvasive diseas; 308 showed symptoms of WN Fever; and 228 cases
showed other or unspecified symptoms.]

A total of 469 (56%) of the 843 cases occurred in males; the median age
of patients was 50 years (range: 1 month--99 years). Illness onset
ranged from April 23 to August 17.

A total of 77 presumptive West Nile viremic blood donors (PVDs) have
been reported to ArboNET in 2004. Of these, 36 (47%) were reported from
Arizona, 16 from California, seven from New Mexico, six from Texas,
three each from Florida and South Dakota, two each from Colorado and
Wisconsin, and one each from Iowa and Missouri. Of the 77 PVDs, two
persons aged 66 and 69 years subsequently had neuroinvasive illness,
and 12 persons (median age: 56 years; range: 22--73 years) subsequently
had West Nile fever.

In addition, during 2004, a total of 2,961 dead corvids and 514 other
dead birds with WNV infection have been reported from 40 states.

WNV infections have been reported in horses from 28 states (Alabama,
Arizona, Arkansas, California, Colorado, Florida, Idaho, Illinois,
Iowa, Kentucky, Michigan, Minnesota, Mississippi, Missouri, Montana,
Nevada, New Mexico, North Carolina, Ohio, Oklahoma, Oregon, South
Dakota, Tennessee, Texas, Utah, Virginia, Wisconsin, and Wyoming) and
in four dogs from Nevada and New Mexico. Three unidentified animal
species with WNV infection were reported from Illinois and Nevada. WNV
seroconversions have been reported in 474 sentinel chicken flocks from
11 states (Arizona, Arkansas, California, Delaware, Florida, Iowa,
Louisiana, Nebraska, Nevada, South Dakota, and Utah) and in two wild
hatchling birds from Ohio. Three seropositive sentinel horses were
reported from Puerto Rico.

  A total of 3,526 WNV-positive mosquito pools have been reported from
31 states (Arizona, Arkansas, California, Colorado, Connecticut,
Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland,
Massachusetts, Michigan, Mississippi, Missouri, Montana, Nebraska,
Nevada, New Jersey, New Mexico, New York, Ohio, Oklahoma, Pennsylvania,
South Dakota, Tennessee, Texas, Utah, Virginia, and Wisconsin).

Additional information about national WNV activity is available from
CDC at http://www.cdc.gov/ncidod/dvbid/westnile/index.htm and at
http://westnilemaps.usgs.gov.

------------------
[2]
CANADA: HEALTH CANADA SURVEILLANCE DATA as of AUG 18, 2004

Source: Excerpted from ProMED-mail ID 20040820.2312 report of Health
Canada Surveillance Data
<http://www.hc-sc.gc.ca/pphb-dgspsp/wnv-vwn/index.html>

Human cases: In addition to 1 probable case previously reported from
Ontario, 2 cases have been reported from the province of Quebec during
the past week. The Ontario case presented with neurological
manifestations, and the condition of the Quebec patients was
unspecified.

Dead birds: In 2004, 238 confirmed WNV-positives from 4 provinces, of
5125 tested throughout Canada. Since previous report one week earlier,
the number of WNV-positive increased by 53, and 345 dead birds were
tested .

Province / tested / presumed positive / confirmed positive
Newfoundland & Labrador / 68 / 0 / 0
Prince Edward Island / 91 / 0 / 0
Nova Scotia / 365 / 0 / 0
New Brunswick / 405 / 0 / 0
Quebec / 633 / 2 / 38
Ontario / 1206 / 3 / 166
Manitoba / 316 / 0 / 16
Saskatchewan / 314 / 0 / 18
Alberta / 533 / 0 / 0
British Columbia / 1170 / 0 / 0
Yukon / 11 / 0 / 0
Northern Territories / 8 / 0 / 0
Nunavut / 2 / 0 / 0 /
Canada total / 5125 / 8 / 238

Equines and other domestic animals: The figures remained unchanged
since the report of Wed 11 Aug 2004. 2
presumptive cases of West Nile virus infection of equines have been
reported; one in Quebec and one in Alberta. A case of West Nile virus
infection of an unspecified species of domestic animal has been
reported from Ontario.

Mosquito pools: 46 mosquito pools (an increase of 36) have tested West
Nile virus positive: one in Alberta, 19 in Manitoba, 13 in Ontario, 2
in Quebec and 11 in Saskatchewan. These are the 1st reports of West
Nile virus infected mosquitoes in Quebec and Saskatchewan.

******
[3]
CANADA: DETAILS
Source: Excerpted from ProMED-mail ID 20040820.2312 from CTV Canada,
News, Fri 13 Aug 2004 [edited]
<http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/
1092431800526_87841000?hub=Canada>

2 probable human cases of the WNV infection have been reported in
Quebec, the provincial Health Department announced on Fri 13 Aug 2004.
One of the probable cases resides in the Saguenay-Lac-St-Jean region,
about 250 km north of Quebec City, and the other is on Montreal's south
shore. Both cases are women; their ages weren't released.

The 1st human case of West Nile illness [in Canada] this year was
reported recently in Windsor, Ontario. The 45 year old woman who became
sick was recovering and has been released from hospital. In 2003, 17
Quebecers were infected with the virus, which is spread by infected
mosquitoes.

The national agency that distributes blood and blood products has
announced it is taking extra precautions against West Nile virus in 2
provinces. The Canadian Blood Services says blood collected in southern
Ontario and southern Saskatchewan will undergo more thorough testing.

West Nile virus first turned up in Canada in August 2001, where it was
found in dead birds and mosquito pools in southern Ontario. The 1st
confirmed human cases were in Quebec and Ontario in 2002. Saskatchewan
was Canada's hardest-hit province in 2003.

--------------------------
[4]
ARIZONA: US EPICENTER of 2004 WNV OUTBREAK -- WHY?

Excerpted from ProMED-Mail ID 20040820.2312, submitted by Dan Moynihan
<moynihan@lpl.arizona.edu>
Source: Tucson Citizen, AP report, Aug 17, 2004
<http://www.tucsoncitizen.com/breaking/081704_westnile.html>

With triple-digit heat and nearly nonexistent rainfall, Phoenix seems
an unlikely spot for this year's WNV epicenter. Yet, federal
health officials say Arizona is the only state where the mosquitoborne
virus is an epidemic. "Minnesota may be the land of a thousand lakes,
but
we're the land of thousands of abandoned swimming pools," says Will
Humble, head of disease control for the Arizona Department of Health
Services. Those swimming pools, plus irrigation canals that slice
through parts of the city, patio misters and lush lawns designed to
remind transplants of gardens they left behind have inadvertently
turned neighborhoods into oases for mosquitoes.

This year, at least 290 of the nation's more than 500 West Nile cases
and 3 of the 14 deaths have been in Arizona. Nearly all the cases have
been in the state's most populous county, Maricopa, which includes the
Phoenix metro area. State health officials estimate at least 30 000
Arizonans may have the virus without knowing it. Some people never have
symptoms at all. Only about 1 per cent of West Nile victims develop the
potentially dangerous inflammation of the brain or spinal cord --
meningitis or encephalitis.

2003 was the 1st year the virus appeared in areas west of the
Continental Divide. It hit Colorado hard and drifted slowly into
Arizona's northeastern tip, then down south. It's now spreading in
California, where at least 116 cases have been reported and at least 5
people have died. Several factors have contributed to Arizona's
outbreak. "It's like the planets, everything has to align" for an
outbreak to occur, said John Roehrig, chief of the Centers for Disease
Control and Prevention's Arboviral Diseases Branch in Fort Collins,
Colorado. While more humid climates have more mosquitoes and are also
more prepared to deal with "nuisance mosquitoes," Arizona isn't. And
while Arizona doesn't have a lot of mosquitoes because of long
stretches of 100-plus degree days, one type of mosquito thrives here:
_Culex tarsalis_. The species is one of the best carriers of West Nile
virus.

_Culex tarsalis_ does well in suburban settings and likes to feed on
humans. The species can breed in small pools of standing water, such as
in
wheelbarrows, kiddie pools and plant saucers. Because the species is so
dominant here, it doesn't have to compete with other types of
mosquitoes for breeding spots. The water that people surround
themselves with to combat the heat can be another major factor. From
the air, pools form a checkerboard pattern across the desert landscape.
Of the approximate 600,000 residential swimming pools in the state,
state health officials estimate about 10 000 are capable of breeding
mosquitoes. "What we've done is create miniature swamps in our back
yard," said David Ludwig, who oversees Maricopa County health
inspectors treating "green" pools with larvicides. Backyard pools are
to Arizonans what ice scrapers are to Alaskans. Pools are everywhere
and considered a necessity by some. But sometimes they are neglected --
by cash-strapped owners who may have a broken pump or who have moved
before the house has sold. The pools can turn to stagnant pond green in
no time. Also, many of the city's older neighborhoods still use
irrigation flooding for lawns, sometimes leaving standing water for
days. They also have tall, mature trees. Besides mosquitoes, birds love
these spots, and they can carry West Nile, too. The primary weapon has
been to spray pesticide at night with fogging trucks that roam the
neighborhoods. Maricopa County officials recently voted to spend more
money to increase the spraying. But they also opted against the aerial
spraying recommended by the CDC. Federal officials are watching to see
whether the county is able to slow the virus's spread.

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Received on Thu Aug 26 13:20:07 2004