Mosquitoes and West Nile Virus
Once again we have reached that time of the year when locally trapped mosquitoes are showing up with West Nile Virus (WNV). As you may know, certain mosquito species are insect vectors for this virus, and if an infected mosquito bites a human it can transmit the virus and cause WNV disease.
Across the nation, it appears that the number of human cases of WNV this year will surpass previous years, and this is likely due to the warm temperatures encountered in the previous winter months. These temperatures allowed mosquitoes carrying WNV to overwinter in the adult stage, and it is believed that they can then carry the virus from one season to the next.
So far this summer, WNV isolates from mosquitoes in our area have been found in Arlington, Belmont, Brookline, Boston, Revere, Winthrop, Everett, Framingham, Lexington, Malden, Medford, Melrose, Newton, Waltham and Wayland. There have been two reported human cases of West Nile Virus in Cambridge, MA.
Because of these findings, we should all take basic precautions to protect ourselves and our families from mosquito bites through the end of the mosquito season. Mosquito activity plummets below 50 F and generally ends with the first frost. It's important to note that mosquitoes are still breeding in the late summer and the generation being hatched now and in the next few weeks will have a much greater likelihood of carrying the virus.
Preventing Exposure to Mosquitoes
Avoid outdoor activities during the time from dusk to dawn, when mosquitoes are most active. If you must be outdoors in the evening, wear a long sleeved shirt, long pants and socks to cover bare skin.
Repellents
The Massachusetts Department of Public Health (MA DPH) recommends using repellents with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), IR3535 (3-[N-butyl-N-acetyl]-aminopropionic acid) or oil of lemon eucalyptus [p-menthane 3, 8-diol (PMD)] according to the instructions on the product label.
DEET products should not be used on infants under two months of age and should be used in concentrations of 30% or less on older children. Oil of lemon eucalyptus should not be used on children under three years of age. Permethrin products are intended for use on items such as clothing, shoes, bed nets and camping gear and should not be applied to skin.
More information on choosing and using repellents safely is included in the MDPH Mosquito Repellents fact sheet which can be viewed online at www.mass.gov/dph/wnv. If you can’t go online, contact the MDPH at (617) 983-6800 for a hard copy.
Eliminate Standing Water
Mosquitoes breed in stagnant or standing water, so it's important to keep these areas dry. Leaving water standing for more than four days can allow mosquito larvae to become adult, biting mosquitoes. Check your house gutters to ensure that they have no clogs that can lead to the formation of puddles. Remove items such as discarded tires, empty buckets, and other vessels that can hold water from outdoor areas. Change the water in bird baths every three days. Turn over wheel barrows when not in use. Drill holes in the bottom of recycling containers and tightly cover trash containers. Keep swimming pools clean and properly disinfected. Remove standing water from pool covers. Turn wading pools on their sides after emptying them at the end of the day. Look for puddles and standing water on your property that do not dry up within four days, and use landscaping to eliminate wet areas.
Updates
For more regular updates about West Nile Virus, please be sure to visit the Cambridge Public Health West Nile web page:
http://www.cambridgepublichealth.org/services/environmental-health/mosquito-borne-diseases/west-nile-virus.php
