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Ripon mosquito Found to have West Nile Virus

West Nile Virus is here again. 

On Thursday, the San Joaquin County Mosquito and Vector Control District announced that mosquitoes that tested positive for the virus – which can be transmitted to humans and can be deadly in certain populations – have been discovered in San Joaquin County. 

The West Nile Virus positive mosquitoes were discovered in traps that were set in both Ripon and Tracy. 

The discovery and subsequent announcement of its arrival came less than a week before the disclosure that mosquitoes had tested positive for the virus last year on June 17. 

“This find serves as a reminder that mosquitoes carry disease that can harm humans. The District does its part in controlling mosquitoes; however, mosquito control is everyone’s responsibility,” said Aaron Devencenzi, Public Information Officer of the District. “Adult mosquito control activities will increase in accordance with our surveillance results.”

With last year being the worst year for concentration of the virus in and around San Joaquin County since 2014 – with a 125 percent spike in the number of confirmed cases of the virus in humans coming between August and September – spraying efforts continued well into the fall in order to eradicate the adult populations that transmit the virus. 

Last year it took just one month after the virus was first detected in traps monitored by the district before a case was confirmed in a human being, although none of the cases proved to be fatal. The disease claimed the lives of people in San Joaquin in 2013 and 2014. 

Routine spraying of rural areas where adult mosquito populations are plentiful have been underway in the county for months, with aerial spraying currently underway along the Mokelumne River in and around Lodi, Acampo, and Woodbridge, while ground spraying continues throughout the rest of the county. 

Rural South Manteca and West Ripon were sprayed back in April and May and will likely be targeted again as the summer progresses. The district also performs spot sprays where virus-heavy mosquitoes are detected. 

And residents are also urged to be aware of “daytime biting” mosquitoes that are a different concern to the agency than the traditional mosquitoes that carry and transmit West Nile Virus. 

In addition to mosquitoes that carry and transmit West Nile Virus which bite mostly at dawn and at dusk, the “yellow fever” mosquito was first detected in Merced County in September 2017 while the “Asian tiger mosquito” is still a concern. The district is requesting that any daytime mosquito bites be reported to them for tracking and potential response and eradication – both mosquito types can carry a variety of mosquito-borne diseases including dengue, yellow fever, chikungunya, and Zika. 

Other mosquito varieties that have been detected in the area can also bite during the day, but the concern over the serious illnesses carried by those two species are of ultimate concern. 

In order to prevent mosquito-borne illnesses from spreading, the district encourages people to take a number of steps to prevent themselves being bitten and being mindful of the hours in which mosquitoes are most active – typically dusk and dawn. 

Those include:

Checking your property for standing water and eliminating it as needed. Abandoned swimming pools were a major breeding ground for mosquitos during the economic downturn, but something as small as an old tire or a bucket that has collected rain or sprinkler water can provide the environment necessary for mosquitos to breed. 

Applying mosquito repellant that contains the ingredients DEET or Picaridin when outdoors in accordance with usage instructions. 

Avoiding being outside when mosquitoes are the most active, which is typically at dawn and at dusk, and especially for the first two hours after sunset. 

Wearing long pants, long-sleeved shirts, and other protective clothing when forced to be outdoors – especially during peak activity times. 

Making sure that windows and doors have tight-fitting screens to keep active mosquitoes outside of the home. 

The virus is typically carried by birds and transmitted by mosquitos who feed on their carcasses and then bite humans. The State of California has a website to report dead birds for removal and subsequent study that can be found at 

To report unusually strong mosquito infestations or daytime biting contact the San Joaquin Mosquito and Vector Control District at 209.982.4675 or visit them on the web at