COUNTY OF SAN MATEO

Inter-Departmental Correspondence

Health Services Agency

DATE:

September 18, 2002

BOARD MEETING DATE:

October 8, 2002

TO:

Honorable Board of Supervisors

FROM:

Margaret Taylor, Director of Health Services

Brian Zamora, Director of Public Health

Scott Morrow, Health Officer

SUBJECT:

Report on West Nile Virus

Recommendation

Accept the Report from the Health Officer on West Nile Virus

Background

Recently there has been a great deal of news about West Nile Virus and its spread throughout the United States. By September 16, 2002 there had been one case reported in California. This report will provide information to your Board on the history and prevalence of West Nile Virus, and on the actions and roles of the County Health Services Agency and the San Mateo County Mosquito Abatement District in protecting the public.

West Nile Virus (WNV) was first isolated in 1937 in the West Nile region of Uganda. It is spread by the bite of an infected mosquito and can infect humans, birds, mosquitoes, horses and some other mammals. The virus became recognized as a cause of severe human meningoencephalitis (inflammation of the spinal cord and brain) in elderly patients during an outbreak in Israel in 1957.  Recent outbreaks of WNV encephalitis in humans have occurred in Algeria in 1994, Romania in 1996-1997, the Czech Republic in 1997, the Democratic Republic of the Congo in 1998, Russia in 1999, the United States in 1999-2001, and Israel in 2000.  Epizootics of disease in horses occurred in Morocco in 1996, Italy in 1998, the United States in 1999-2001, and France in 2000 and in birds in Israel in 1997-2001 and in the United States in 1999-2002. There is no evidence to suggest that WNV can be spread directly from person to person or directly from animal to person.

Discussion

Most people who are infected with WNV will not have any type of illness. Fewer than 20% of the people who become infected will develop West Nile fever (symptoms include: mild symptoms, including fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands). Fewer than 1% will develop more severe disease in the form of meningitis and/or encephalitis (Symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. In rare instances death may occur. Persons over 60 years of age are considered at highest risk. It is likely that persons with immune compromising conditions are also at higher risk.

The Health Services Agency has undertaken extensive and on-going activities to notify local physicians, emergency rooms, and hospitals of the risk of spread of WNV since early August, 2002. Local health care providers are required to notify Public Health when they have a suspected human case; samples are sent to the state lab for analysis of blood and spinal fluid.

The San Mateo County Mosquito Abatement District (SMCMAD) has recently completed an updated Arbovirus Surveillance and Response Plan that includes WNV prevention and interdiction. The plan meshes smoothly with pre-existing abatement and surveillance activities and includes the following key areas:

Maintain local state and federal health surveillance and reporting agencies.

Continue aggressive prevention and suppression of adult mosquito.

Perform ongoing surveillance of adult mosquitoes throughout the District.

Maintain and monitor sentinel chicken flocks.

Avian (dead bird) surveillance and submission to the state health department lab.

Human cases will be monitored through ongoing close relationships with the Health Officer and Public Health.

Outreach and Public Education campaigns.

The public can help by reporting dead birds to the State Health Department at: (800) WNV-BIRD or (800) 968-2473. Dead birds in the County can be tested by calling that number or the SMCMAD at 650-344-8592. The public should also call when they see increases in adult mosquitoes in their area SMCMAD staff will respond and investigate to discover whether new areas of mosquito breeding have developed. The District covers only those cities that have previously agreed to participate and small areas of unincorporated San Mateo County. The district does not cover north county, some areas of south county, and the coastside, which is about two-thirds of the County area.

Vision Alignment

This report kept the commitment of Ensuring basic health and safety for all and goal number 7: Maintain and enhance the public safety of all residents and visitors. The report contributes to this commitment and goal by reporting on the actions underway and to be taken to protect the public from West Nile Virus.

Fiscal Impact

There is no fiscal impact to accepting this report. The current activities in Public Health are part of the responsibilities of the Disease Control and Prevention Unit and are funded in the 2002-2003 approved budget.