WEST NILE VIRUS, HUMAN SURVEILLANCE 2000 - USA
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[see also:
2000
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West Nile virus, human case - USA (Connecticut) 20001020.1813
West Nile virus, human case - USA (New York) 20000804.1303
West Nile virus, human case - USA (New York) (07) 20001005.1716
West Nile virus, human cases - USA (New Jersey) 20001227.2287
West Nile virus, human cases - USA (New York) 20000813.1345
West Nile virus, human cases - USA (New York) (03) 20000825.1424
West Nile virus, human cases - USA (NY & NJ) 20000902.1484
West Nile virus, human cases - USA (NY & NJ) (03) 20000927.1672
West Nile virus surveillance - USA 20000720.1198
West Nile virus surveillance - USA (54) 20001223.2267]
Date: Fri 13 Apr 2001
From: ProMED-mail <[EMAIL PROTECTED]>
Source: MMWR Weekly, 13 Apr 2001 / 50(14); 265-8 [edited]
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5014a3.htm>
Human West Nile Virus Surveillance - Connecticut, New Jersey, & New York, 2000
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West Nile virus (WNV), a mosquito-borne arbovirus identified in New York in
1999, has become enzootic in the northeastern United States, affecting
humans, birds, horses, and other mammals. Although no human WNV infection
was identified in Connecticut or New Jersey in 1999, 62 persons with WNV
illness, including 7 deaths, were detected in New York City (NYC) and
nearby New York counties. In 2000, these jurisdictions implemented active
surveillance (AS) and enhanced passive surveillance (EPS) to detect human
illness; 21 persons were identified with acute WNV infection (14 in New
York, 6 in New Jersey, and one in Connecticut), including 2 deaths (one
each in New York and New Jersey). This report summarizes the human WNV
surveillance systems in Connecticut, New Jersey, New York, and NYC and
recommends EPS for hospitalized patients with encephalitis of unknown
etiology for the continental United States.
Connecticut
The Connecticut Department of Public Health (CTDPH) implemented EPS
statewide from 1 Apr 2000 to 31 Oct 2000 and AS in 2 southwestern counties
from 1 Jul 2000 to 31 Oct 2000. Surveillance criteria included all
hospitalized patients with encephalitis, meningoencephalitis, or
Guillain-Barre syndrome (GBS) with fever; in August, criteria were expanded
to include hospitalized aseptic meningitis patients aged >18 years. EPS
consisted of monthly mailings to physicians and all acute care hospitals to
solicit reports of patients meeting surveillance criteria. In counties
participating in AS, infection-control practitioners (ICPs) were asked to
review emergency department and hospital admissions and report patients
meeting surveillance criteria. ICPs were contacted weekly by CTDPH staff
for follow-up on all reported patients. Serum and cerebrospinal fluid (CSF)
specimens from all reported patients were tested for WNV-reactive IgM by
enzyme-linked immunosorbent assays (ELISA) at the CTDPH laboratory.
Between 1 Apr 2000 and 31 Oct 2000, 235 patients were tested: 46 (20%) with
encephalitis or meningoencephalitis, 44 (19%) with aseptic meningitis, and
one (<1%) with GBS; 144 (61%) patients did not meet surveillance criteria
but were tested at their physicians' requests. Of these 235 patients, one
mildly symptomatic outpatient tested positive for WNV. Tested patients were
not categorized by surveillance method.
New Jersey
The New Jersey Department of Health and Senior Services implemented EPS
statewide from 1 Jun 2000 to 30 Nov 2000, and AS in 6 counties near NYC
during from 15 Jul 2000 to 31 Oct 2000. Surveillance criteria included all
patients hospitalized for viral encephalitis, meningoencephalitis, or GBS
and patients aged >17 years with aseptic meningitis. For EPS, public health
staff distributed WNV fact sheets, surveillance criteria, and reporting
instructions to health-care providers. For AS, ICPs in 6 counties reviewed
emergency department and hospital admissions, surveyed physicians, and
provided weekly fax reports of patients meeting surveillance criteria. ICPs
and physicians were contacted weekly for follow-up on all reported
patients. Serum and CSF specimens from patients who met the surveillance
criteria were tested for WNV-reactive IgM and IgG by ELISA at the state's
Public Health and Environmental Laboratory.
Of 55 patients tested, 18 (33%) had encephalitis, 15 (27%) had
meningoencephalitis, 19 (35%) had aseptic meningitis, and 3 (6%) had GBS. A
total of 6 patients had laboratory evidence of WNV infection; 5 (83%) were
identified through EPS and one (17%) through AS.
New York City
The New York City Department of Health (NYCDOH) implemented EPS citywide
from 1 May 2000 to 25 Nov 2000, active physician-based surveillance (APS)
from 1 Jun to 30 Sep 2000, and active laboratory-based surveillance (ALS)
from 1 Jul to 30 Sep 2000. Surveillance criteria included all hospitalized
patients with encephalitis, meningoencephalitis, or GBS with fever or
altered mental status and patients aged >17 years with aseptic meningitis.
For EPS, public health staff provided surveillance criteria and laboratory
testing information to health-care providers through medical rounds,
biweekly alerts, and a special issue of the NYCDOH's medical bulletin. APS
was conducted at 18 sentinel sites; infectious disease and critical-care
specialists and neurologists and chief medical residents were contacted
biweekly for reports of patients meeting surveillance criteria. A total of
12 sites participated in ALS; hospital microbiology laboratories submitted
CSF specimen results with parameters suggesting viral etiology for testing
on a weekly basis. APS and ALS sites were selected initially on the basis
of 1999 WNV activity; additional sites were added during the season as
increasing WNV activity in birds and mosquitoes was detected in Staten
Island and south Brooklyn. All serum and CSF specimens were tested for
WNV-reactive IgM by ELISA at the NYC Public Health Laboratory.
Of 512 patients tested, 205 (40%) had encephalitis or meningoencephalitis,
236 (46%) aseptic meningitis, 22 (4%) GBS, 41 (8%) other diagnoses, and 8
(2%) unknown diagnoses; 56 (11%) did not meet surveillance criteria but
were tested at their physicians' request. A total of 14 NYC residents had
WNV infection diagnosed; 11 (79%) infections were detected at APS hospitals
and 3 (21%) at hospitals where only EPS was conducted; 2 patients with WNV
infection reported by physicians were identified simultaneously through ALS.
New York State (excluding NYC)
From 1 May 2000 to 31 Oct 2000, the New York State Department of Health
(NYSDOH) and local units conducted EPS statewide and AS in counties with
WNV activity in humans, birds, mosquitoes, or horses in 1999 or 2000; in
April, NYSDOH implemented commercial laboratory surveillance. Surveillance
criteria included all patients with viral encephalitis or
meningoencephalitis and patients aged >2 years with aseptic meningitis. EPS
included distributing alerts that encouraged physician reporting and
specimen submission instructions to all local health units. Suggested
activities for local health units conducting AS included weekly contact
with medical staff at sentinel acute-care hospitals about patients meeting
surveillance criteria. Commercial laboratories licensed by NYSDOH to
perform arbovirus testing participated in surveillance by reporting
patients who tested positive for antibodies to arboviral panels. Serum and
CSF specimens from reported patients were tested for WNV infection at the
New York Wadsworth Laboratory; testing included WNV-reactive IgM and IgG by
ELISA, polymerase chain reaction, and plaque-reduction neutralization.
Of 589 patients tested, 230 (39%) had encephalitis or meningoencephalitis,
191 (32%) had aseptic meningitis, 89 (15%) did not meet surveillance
criteria, and 79 (13%) were missing data to determine clinical status.
Tested patients were not categorized by surveillance method. Commercial
laboratory surveillance identified 4 patients who had flavivirus
antibodies; investigation by local health units for travel and vaccination
history and additional WNV testing indicated that none had a current or
non-travel-related flavivirus infection. No human WNV infection was
identified in New York outside of NYC.
MMWR Editor's Note
In 2000, public health jurisdictions used active and passive surveillance
approaches based on staff and laboratory resources and degree of WNV
activity identified by bird, mosquito, and mammalian surveillance. AS
fostered ongoing communication between health departments and health-care
providers but had variable yield. A total of 11 of 14 WNV-confirmed
patients from NYC but only one of 6 in New Jersey were identified at AS
hospitals. AS could have identified a higher proportion of WNV illnesses in
NYC because the location of AS coincided with the epicenter of the outbreak
(Staten Island). In comparison with AS, EPS was less labor-intensive for
health-care providers and health department staff, and intense public
awareness of WNV in the northeast United States may have improved EPS
effectiveness, resulting in increased reporting. However, EPS did not
provide direct education about WNV to health-care providers, and in the
absence of media and public interest, EPS may have missed reports of
suspect illnesses. To plan future surveillance strategies, jurisdictions
should evaluate the costs and yields of active and passive WNV surveillance
efforts in upcoming transmission seasons. All jurisdictions focused
surveillance on severe WNV manifestations. Serologic studies suggest that
approximately one in 150 infected persons develop neurologic disease
requiring hospitalization. By monitoring patients with severe disease, the
number of infected persons can be estimated; however, jurisdictions with
few non-hospitalized human WNV infections may not be identified.
Surveillance among patients with mild and nonspecific symptoms (e.g., fever
and headache) probably would exhaust laboratory and staff resources.
Most states did not conduct WNV testing on pediatric patients with
meningitis in summer months because they most likely represented
enteroviral infections. In addition, most 1999 human infections were
identified in older hospitalized patients. Therefore, studies during
outbreaks should be considered to determine the spectrum of clinical
illness and the extent to which children are affected.
In 2001, EPS for hospitalized patients with encephalitis of unknown
etiology is recommended for the continental United States. All suspect WNV
illnesses should be screened by testing CSF and appropriately timed acute
and convalescent serum specimens for IgM ELISA antibody. Appropriately
timed acute and convalescent serum samples should be tested for a 4-fold or
greater rise in WNV-specific neutralizing antibody. With the availability
of commercial laboratory testing for WNV, jurisdictions are encouraged to
identify patients with commercial laboratory reports indicative of recent
WNV infection and to verify these results by viral-specific neutralizing
antibody testing. Monitoring of milder illnesses (e.g., aseptic meningitis
or GBS) depends on jurisdictions' resources and should be a lower priority.
AS should be considered in areas with known WNV activity on the basis of
bird and mosquito surveillance data. Jurisdictions in the northeastern,
central, and western United States should begin human surveillance by June
2001 or earlier if other surveillance activities, such as avian mortality
surveillance, demonstrate WNV activity. WNV could circulate throughout the
year in some areas, especially the Gulf States; therefore, human
surveillance should be considered year round in southern states. Because
the ELISA and hemagglutination-inhibition test can be cross-reactive
between WNV, St. Louis encephalitis, yellow fever, dengue, and Powassan
viruses, patients who test positive for antibodies to these viruses should
be tested for specific neutralizing antibody.
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