WNV--End of Year Summary & Update

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Largest Reported WNV Epidemic: "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.

Intrauterine, Transplacental (Vertical) Transmission: 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].

Infection from Handling Infected Animals: 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.

Range of WNV in North America: 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.

Possibly in the UK: BBC reported on Oct 28 that researchers at the
Oxford University-based Centre for Ecology and Hydrology have found
WNV antibodies in non-migratory birds in the UK. These findings
suggest presence of WNV in the UK, but no cases of WNV caught in
Britain have been reported [More].

Human cases in US: 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.
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.

Human cases in Israel: 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.

Update on Raptors: 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.]

Equine 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).

Marine mammal death: Sirrus, a 12-year-old harbor seal at the New
Jersey State Aquarium, is recently confirmed to have died Sept 22
from WNV-infection (disease onset Sept 12)--the first confirmation of
a marine mammal dying from WNV in the US. The seal had no health
problems after living in the saltwater exhibit for 10 years and how
he became infected is unclear. Test results are also pending on the
cause of the Sept 2 death of a 23-year-old gray seal at the National
Zoo in Washington DC.

--
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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