- By Lois Levitan, PhD
- Program Leader - Environmental Risk Analysis Program
- Center for the Environment - Cornell University
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- LARGEST REPORTED WNV EPIDEMIC
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- The 2002 WNV epidemic in the US was the largest arboviral
meningoencephalitis epidemic documented in the western hemisphere and the
largest reported WNME epidemic. Epizootic and epidemic activity was most
intense in the central US, especially in the Great Lakes region, and extended
to the west coast... [indicating] complete transcontinental movement of
WNV within 3 years." These are some of the key points made in the
Dec 20 MMWR (Morbidity and Mortality Weekly Report) from the Centers for
Disease Control (CDC) in summarizing information reported through Nov 30
2002 via ArboNET, a web-based data network through which 54 state and local
public health departments report results of surveillance activities. Other
information is incorporated into pertinent sections of ERAP's WNV summary
pages.
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- INTRAUTERINE, TRANSPLACENTAL (VERTICAL) TRANSMISSION
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- An infant born in November to a woman who contracted
WNV while pregnant is hospitalized in Syracuse, New York (Onondaga County
Health Dept, PR Dec 18, 2002). "WNV has not previously been associated
with intrauterine infection or adverse birth outcomes" in the formal
record, although at least one other human case of transplacental transmission
has been described anecdotally. Details are described in the CDC MMWR Dec
20, 2002 and were also covered in the Dec 19 CDC press conference. CDC
recommends that "pregnant women should take precautions to reduce
their risk for WNV or other arboviral infection and should undergo diagnostic
testing when clinically appropriate." [For additional information
and background, see WestNileVirus-l listserv postings from Oct 13, 15,
and 17 and Dec 20].
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- INFECTION FROM HANDLING INFECTED ANIMALS
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- At least 2 US lab workers became infected with WNV in
2002 when their skin was cut while handling infected animals. These cases
of "percutaneous inoculation" are described in the Dec 20 MMWR,
which recommends precautions that should be taken by labs -- e.g., avoiding
contact with fluids, tissues and aerosols -- and presumably also heeded
by hunters and others who might come in contact with infected animals.
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- RANGE OF WNV IN NORTH AMERICA
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- In 2002 WNV has been detected in 44 states (2,289 counties)
across the US and 5 provinces in Canada, from Saskatchewan to Nova Scotia.
In the US the only states where it has not been detected are Alaska, Arizona
(several cases imported from elsewhere), Hawaii (case in infected tourist
from Minn), Nevada, Oregon (it has been found in a human case contracted
elsewhere and in a horse in a border county in Idaho) and Utah. In many
states WNV has been detected in all, or nearly all, counties, including
several on the Mexican border [Dec 7, 2002 range map]. The 2002 range compares
with 359 counties in 27 states and Washington DC in 2001. Despite this
large increase, CDC believes that the ArboNET data reported in their Dec
20 MMWR likely underestimate the actual geographic range and intensity
of WNV transmission in the US because (a) only 27% of birds reported in
2002 were tested as compared with 50% in 2001; (b) some data are not yet
reported; and (c) there is not a nationwide surveillance case definition
for WNME and WNF.
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- HUMAN CASES IN US
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- As of Dec 19, 2002 CDC reports 3,852 human cases (232
fatalities) from 39 states and Washington DC (as compared with 149 human
cases accounted by CDC 1999-2001). This is an increase of a little more
than 100 cases in the 3 weeks since Nov 26 (3,737 cases, 201 fatalities).
Illinois (778), Michigan (553), and Ohio (431) have the highest case loads.
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- Of 3,389 cases reported in the Dec 20 MMWR, 69% were
persons with WN meningoencephalitis (199 fatalities among 2,354 cases,
= 9% fatalities), 21% with what is being referred to as WN fever (2 of
704 cases fatal, = 0.3%, both persons over 80), and 10% with unspecified
illness. The epidemic peak was during the week ending August 24 (317 cases
in northern states), a week later than the peak in the southern states
(88 cases in southern states week ending Aug 17) [Case load graph]. Among
all reported human cases median age=55 (range 1 months-99 yrs, 54% male);
for persons with WNME median age=59, same range; for persons with WNF median
age=48 (range 1-93 yr). Median age of 201 decedents=78 (range 24-99); 60%
deaths male.
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- HUMAN CASES IN ISRAEL
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- The Health Ministry ann Oct 16 that there have been
26 human cases of WNV in Israel in 2002 (2 fatalities), which is comparable
to the case load in 2001 and about 5% the number of human cases in 2000.
WNV-positive mosquitoes were detected as early as May this year, as compared
with first detections in Aug in previous years.
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- UPDATE ON RAPTORS
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- The University of Minnesota's Raptor Center had reported
increasing numbers of raptors picked up sick or dead earlier this fall,
and thought to be infected with WNV. Dr. Emi Kate Saito, WNV Surveillance
Coordinator with the National Wildlife Health Service updated this information
as of Dec 18, 2002: "The National Wildlife Health Center (NWHC) has
tested some of the raptor cases admitted to raptor rehabilitation centers.
These cases underwent full diagnostic evaluation to determine whether the
deaths were due to WNV or to other causes. The NWHC WNV testing protocol
consists of isolating virus from organ tissues (such as kidneys, spleen,
brain, etc.) and then performing RT-PCR on the virus isolates to confirm
WNV. Other tests include looking for other infectious causes (bacterial,
fungal or other viral) and toxin exposure. As of December 18, 2002, the
NWHC had received 73 raptor carcasses from several states. Diagnostic evaluation
has been completed for 30 cases : 9 died due to WNV, 6 were infected with
WNV but did not show any or sufficient brain damage to explain symptoms,
4 were WNV-negative but had sufficient brain damage suggestive of viral
encephalitis, and 11 died from other causes. In sum, NWHC has diagnosed
9 confirmed and 10 possible cases of WNV. Further confirmatory testing
is planned for the 10 possible cases." [For additional information
see WestNileVirus-l listserv postings from Sept 13, 15, 18, 23 and December
19, as well as ERAP's Summary on WNV and birds.]
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- EQUINE CASES
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- As of Dec 1, 2002, USDA APHIS reports 14,358 equine cases
of WNV-illness either confirmed at USDA's National Veterinary Services
Laboratories (NVSL) or reported by state officials in 2002. This is an
increase of 313 cases since the previous report on Nov 20. Case numbers
had been increasing at a rate of 400-500 per week since Oct 20, when 11,526
cases were reported. llinois, Iowa, Nebraska, and Texas each have more
than 1000 equine cases. Minnesota, Missouri and Oklahoma have nearly as
many. In Texas the 1377 cases represent about 0.15% of the million horses
in the state. CDC reports many fewer cases in the current MMWR (9,038 equines,
3 canines, and 10 other species). [More about Horses]. WNV has now been
associated with illness and death in several other mammal species including
reindeer, mountain goats, squirrels, etc. [More]. The Nov 29, 2002 CDC
MMWR also reports WNV infection from 42 states and Washington DC in thousands
of dead birds (7,715 dead crows and 6,275 other dead birds).
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- This summary is slightly revised from the "Latest
News" posted on ERAP's West Nile Virus
- webpages. Weblinks are "live," while links
in this email are not
-
- Lois Levitan, PhD Program Leader
- Environmental Risk Analysis Program
- Center for the Environment
- 213 Rice Hall, Cornell University
- Ithaca, New York USA 14853-5601
-
- Phone (607) 255-4765 Fax: (607) 255-0238
- Email LCL3@cornell.edu
-
- Program Email: envrisk@cornell.edu
- Web:http://www.cfe.cornell.edu/ERAP
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