The Threat of West Nile Virus in the IE?

The Threat of West Nile Virus in the IE?

S. E. Williams


Vector Control units in both Riverside and San Bernardino Counties are working aggressively to trap, monitor and report West Nile infected mosquitoes in the Inland Empire. In the meantime, citizens are being impacted by the West Nile Virus.

West Nile Virus is a viral neurological disease considered less deadly than other mosquito born viruses. The vast majority of people infected with the disease remain asymptomatic; although at times, the virus can also be deadly. According to the Center for Disease Control (CDC) the disease has killed more than 1200 people in America since it was first identified in the states in 1999.

2015 is proving to be an active year for to the disease in Riverside County. According to official tracking by the California Department of Public Health, as of October 20th there were 66 reported cases of the disease in Riverside County—second only to Los Angeles County. By comparison, there were 25 reported cases in San Bernardino County.

In an exclusive interview with The Voice, Riverside County Department of Environmental Health Program Chief, Dottie Merki, was asked her opinion regarding this year’s West Nile Virus activity.

“There isn’t always a specific, scientific reason for any area getting a higher incidence than other areas,” she replied. “Some of the contributing factors could be rain followed by periods of hot weather.”

Other factors identified by Merki included unkempt backyard swimming pools and drought conditions that have caused more pockets of stagnant water. “Bird migration is always a factor in the transmission as well, she said. “Birds are the host reservoir.”

In a separate interview with the Riverside County Director of Disease Control, Barbara Cole, she reminded the community that cases of West Nile Virus (WNV) vary from year to year based on a number of factors that include both the mosquito population and the number of birds infected with the disease. “It is a combination of factors,” she explained. “You must look at several years to determine a trend.”

“In other years the numbers were just as high,” Cole explained. “Our highest year [on record] in Riverside County was 2005. We had 103 cases reported.” She continued, “In 2008 there were 62 cases; in 2011, there were 7 cases; in 2012, 19 cases; in 2013, 35 cases; and, the total dropped to 15 cases in 2014.”

Cole believes it is also possible some of the virus’s reported increase in activity may be partly a result of increased awareness about the disease. This could lead to more awareness of the disease’s symptoms, increased testing and as a result—more reporting. (Based on CDC guidelines, WNV is a reportable disease).

Parts of Riverside County are more impacted than others this year. According to Merki, “They include Moreno Valley, Nuevo, and Perris.” To view a map of WNV activity in your area visit Riverside County’s website (web link can be found at the end of this article).

Appropriate agencies in the Inland Empire are working aggressively to manage this year’s outbreak. Merki explained how Vector Control staffs have increased surveillance in areas known to be mosquito breeding habitats. “We have also increased our outreach to educate the public on how to eliminate mosquito breeding sites from their property, as well as how to protect themselves from mosquito bites.” Also, according to Merki, Vector Control staffs have basically shifted all resources to combating the mosquitoes this year.

“We feel both measures are working,” she continued. “More of the public are reaching out to us to call in areas of stagnant water they discover and ask more questions on what they can do to protect their communities.”

According to Cole, Riverside County’s Department of Disease Control sends health advisories to doctors, public health officials and hospitals regarding vector born diseases like West Nile Virus each year in May and again in December.

2014 was a record year in California for West Nile Virus activity. The state experienced the second-highest number of human cases since the virus first invaded the state in 2003 with a total of 801 cases. As of October 20th, the state has recorded 366 cases. The state’s previous record was set in 2005 with a total of 880 cases of the virus.


Although 2014 was the second most active year on record, the California Department of Public Health (CDPH) reported the state did see several other records broken with the increased activity in WNV last year as follows: Firstly, there was an increase in the number of cases of neuro-invasive WNV, the more serious neurological form of the disease that can lead to encephalitis or meningitis. Secondly, the 31 fatal cases of the disease experienced last year exceeded the number of deaths experienced in all previous years. So far this year there are 18 reported fatalities in the Inland Empire, (four in Riverside County and two in San Bernardino County). The number of mosquitoes infected with WNV was the highest level ever detected in the state in 2014 (the mosquito infection rate equaled 6.0—5.0 or above is considered an epidemic). Finally, the prevalence of WNV infection tested in dead birds stood at 60 percent, the highest ever detected in California.

In April, CDPH Director and State Health Officer, Dr. Karen Smith, expressed concern regarding how the ongoing drought may have contributed to WNV activity because it has resulted in more limited sources of water for birds and mosquitoes. “As birds and mosquitoes sought water, they came into closer contact and amplified the virus, particularly in urban areas,” she hypothesized and continued, “The lack of water could have caused some sources of water to stagnate, making the water sources more attractive for mosquitoes to lay eggs.”

WNV is transmitted to humans through the bite of an infected mosquito that has first feasted on dead birds. Signs and symptoms of WNV can include fever, body aches, rash, nausea, vomiting and headache.

Although most people infected with the virus have no symptoms, some develop severe symptoms which can lead to brain inflammation or paralysis. People 50 years-of-age or older and people with diabetes and/or high blood pressure are at greatest risk of developing serious complications from this infection.

County of San Bernardino Public Health Administrator Dr. Maxwell Ohikhuare has warned, “West Nile Virus infection can cause serious disease; therefore, prevention is essential.”

There is no question the most effective way to avoid WNV infection is to prevent mosquito bites. Readers are encouraged to protect themselves and their loved ones from mosquito bites by taking the following precautions recommended by numerous public health officials: Dawn and Dusk–avoid spending time outside when mosquitoes are most active; Dress–wear shoes, socks, long pants and long-sleeved shirts that are loose fitting and light colored; Drain–remove or drain all standing water around your property where mosquitoes lay eggs (birdbaths, ponds, old tires, buckets, clogged gutters or puddles from leaky sprinklers); DEET–apply insect repellent containing DEET. When using DEET, be sure to read and follow the labeled instructions; Doors–make sure doors and windows have tight-fitting screens. Repair or replace screens that have tears or holes to prevent mosquitoes from entering the home.

In the coming weeks, the traditional West Nile Virus season should come to a quiet close. “Normally, the mosquito populations and therefore the cases of West Nile Virus decrease in the fall when the weather turns cooler,” Merki shared. “We have no reason to expect anything different this year, but of course, it is all dependent on the weather.”

Finally, readers are encouraged to report green or neglected pools of water by calling 1 (800) 442-2283 and pressing 3 when prompted. Readers can also participate in the WNV surveillance program by reporting dead birds to the state’s WNV toll-free hotline at (877) WNV-BIRD (968-2473) or For more information on West Nile Virus please visit Riverside County Vector control at San Bernardino County Mosquito and Vector Control Program at

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