Discovery of bugs carrying West Nile virus makes San Mateo County ‘very concerned’ about possible threat to humans

Discovery of bugs carrying West Nile virus makes San Mateo County ‘very concerned’ about possible threat to humans

San Mateo County said that it’s quite worried about the probable danger of humans getting infected by West Nile virus after the discovery of mosquitoes and dead birds containing the virus numerous times in the region over the last 30 days.

The county will fog for mosquitoes in portions of Atherton and the unincorporated county tonight, beginning at 9 pm, where insects carrying the virus were discovered Wednesday.

The Mosquito and Vector Control District is going to treat a region ranging from Hull Avenue to the west, Alameda de las Pulgas to the south, Camino Al Lago to the east and Austin Avenue to the south till 5 am Friday. The region includes parts of West Atherton, where insects with the virus were discovered on July 28, excluding a portion of the neighborhood north of Austin. The area will also include a huge strip of the neighborhood south of Selby Lane.

In an email, Megan Caldwell, the district's outreach officer, said, “Mosquitoes collected from last week's treatment area were clear, but we found infected mosquitoes in another area nearby. We're very concerned about the risk of West Nile in this area”.

The district started collecting and testing mosquitoes when it found seven lifeless crows infected with the virus in Atherton and Redwood City in July. The crows were found in Redwood City’s West Atherton and in the Eagle Hill-Mount Carmel area. The treatment map area can be seen on at www.smcmvcd.org.

According to the district, once the treatment is completed, mosquitoes’ collection process will start again. If samples are found to still be carrying the virus, extra fogging could be required.

The district spokeswoman Megan Caldwell said that during the hot weather, the virus duplication occurs more quickly in mosquitoes due to which the prevalence is more likely in the South Bay in comparison to the north.

According to a report in Mercury News by Kevin Kelly, "The county will fog for mosquitoes in portions of Atherton and the unincorporated county tonight, beginning at 9 p.m., where insects carrying the virus were discovered Wednesday. The Mosquito and Vector Control District will treat an area bounded by Hull Avenue to the west, Alameda de las Pulgas to the south, Camino Al Lago to the east and Austin Avenue to the south from 9 p.m. tonight to 5 a.m. Friday, weather permitting."

"Mosquitoes collected from last week's treatment area were clear, but we found infected mosquitoes in another area nearby." said Megan Caldwell, the district's outreach officer, in an email. "We're very concerned about the risk of West Nile in this area."

Replication of the virus in mosquitoes occurs more quickly during hot weather, which is "why there tends to be more in the South Bay than the north," according to district spokeswoman Megan Caldwell. The native Culex pipiens mosquito is primarily responsible for the spread of West Nile virus in the Bay Area.

A report published in UMN informed, "WNV infection occurs when the virus spills over to humans, via mosquito bites, from mosquito and bird populations. Though one-third of birds in Atlanta carry WNV, human transmission rates are very low (about 3.3 per 100,000 people per year). Chicago has a similar percentage of birds carrying WNV, but more than five times the incidence of WNV in humans (about 16.2 per 100,000 people)."

"[C]ardinals, even though they can be infected with West Nile virus, are much less likely to have enough virus circulating in their blood to transmit the disease back to feeding mosquitoes. That is why we called them ‘supersuppressors,'" Rebecca Levine, PhD, lead author of the study, said in a press release from the journal. She conducted the research while at Emory University.

In a press release from Emory University, Levine said, "This finding suggests that old growth forests may be an important part of an urban landscape, not just because of the natural beauty of ancient trees, but because these habitats may also be a means of reducing transmission of some mosquito-borne diseases."

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