West Nile Virus activity wanes as temperatures drop, but the Marin/Sonoma Mosquito and Vector Control District announced this week that five more infected birds—one in San Rafael—tested positive.
That brings a total of five WNV-positive birds in Marin County this year - in San Rafael, Novato, Ross, Corte Madera and Greenbrae - but the number isn’t expected to rise by much this year.
“During the summer is when WNV transmission is most likely to occur due to the abundance of vector mosquitoes as well as the warmer weather,” said Nizza Sequeira, the district’s public relations director. “We actually do have mosquitoes year round in both Marin and Sonoma counties but they are most abundant during the spring and summer months and begin to taper off into fall.”
That’s not to say all mosquito activity comes to a halt.
“As we enter the cooler months mosquitoes are not as active but will continue to reproduce,” said Sequeira. “For example, we will see more of what we call the cool-weather mosquito (Culiseta incidens) and the large winter mosquito (Culiseta inornata).”