October 26, 1999

PLEASE DISTRIBUTE TO INTERNAL MEDICINE AND PEDIATRIC STAFF, EMERGENCY ROOM, INFECTIOUS DISEASE, NEUROLOGY, INTENSIVE CARE UNIT AND AMBULATORY CARE STAFF

Dear Infection Control Practitioners, Infectious Disease Physicians, Emergency Department Directors, and Laboratory Directors:

Mosquito surveillance in Westchester County indicates that mosquito counts have decreased significantly following insecticide spraying and in response to decreasing temperature and daylight. No further spraying for mosquito control is therefore planned at this time in the absence of new information. Despite the significantly decreasing risk of mosquito bites due to the above factors, recent bird deaths and (+) testing in such birds for West Nile virus indicates that local transmission is still possible and may be ongoing.

Thus, individuals are advised to continue taking appropriate precautions against mosquito bites (Refer to Westchester County Health Department web site at top of document for information sheets for patients):

avoiding likely mosquito habitats when possible,

wearing long-sleeved clothing,

using DEET containing insect repellants on exposed skin,

ensuring tightly fitting screens in good repair in their homes,

removing potential mosquito breeding sites – any standing water in their yards or property (flower pots, gutters etc.), including swimming pools.

These precautions by individuals and surveillance for West Nile infection in humans and animals by the Westchester County Health Department should/will be continued until there is sustained frost and surveillance indicates no further local transmission of West Nile virus.

Thank you for your continued efforts and assistance in responding to this outbreak.

Can my pet get sick from this disease?

West Nile virus has recently been detected in at least one dead horse in Suffolk County, Long Island. The virus is probably also responsible for illness in several other horses in that area. There is no evidence to date that dogs or other domestic animals have become clinically ill from this virus during this outbreak. A veterinarian should be consulted to evaluate any pets or domestic animals that become ill. Laboratory testing of ill animals is available through coordination of state and federal agencies with local veterinarians. While the evidence points to mosquitoes as the most important means of transmission, people who directly handle neurologically ill animals or their tissues should take precautions such as wearing gloves. Such precautions can also help protect against contact with saliva of sick animals that may actually have rabies rather than West Nile virus infection.

No, this is very unlikely. People get infected by a mosquito bite. However, it's critical when handling any animal with encephalitis to wear gloves and avoid contact with saliva and nervous tissue, because the animal could have rabies, a fatal disease.

It may be advisable to keep horses inside a barn at night with the doors closed to reduce the probability of getting a mosquito bite. Insect repellents may be used as well.

When I vaccinate my horse against Eastern, Western, or Venezuelan Encephalitis, will that protect against infection with West Nile?

The equine encephalitis viruses belong to a different family of viruses from that of the West Nile virus. Therefore, vaccines are not expected to provide cross-protection. Further research will be done in this area.