As the number of West Nile virus cases ratchet up locally and nationally, Merced County announced their first fatality from the virus.
The Merced County Public Health Department reported the death of an 86-year-old woman from West Nile virus. The woman was infected in August and died this month. There have been five human cases reported in Merced County, as of Thursday.
Stanislaus County, as of Thursday, had 12 human cases of the virus, the most of any other county in California, according to the data collected by California’s Public Health Department and the state-run West Nile virus website.
Statewide, 34 counties have reported the presence of the virus, including 17 with human cases. There have been 75 human cases in California and four fatalities, including the recent death in Merced County.
Across the country, there have been 1,993 human cases reported as of Tuesday and 87 fatalities, according to the Centers for Disease Control. Of these, 1,069 or 54 percent were classified as neuroinvasive disease, such as meningitis or encephalitis, and 924, or 46 percent, were classified as non-neuroinvasive disease. The numbers reflect a 25 percent increase in cases from the week before, according to the CDC.
A majority of the outbreak has occurred in Texas, where there have been 888 human cases and 35 deaths.
The West Nile virus has been detected in 48 states.
The 12 people in Stanislaus County sickened with the virus range in age from 6 years old to 74 years old. Of the 12, five have been diagnosed with the neuroinvasive form.
The CDC is calling this year the largest outbreak of the virus since it was detected in 1999.
It’s unknown what is causing the increased number of cases, but CDC officials believe weather may be a factor.
“One of the things we are closely looking at is the effect of weather on this year's outbreak,” said Dr. Lyle Petersen, the director of the Division of Vector-borne Infectious Diseases at the CDC. “We know that West Nile virus outbreaks tend to occur when the temperature is above normal, and of course, this year's heat wave was record setting. So we think the temperature may have — may be influencing this year's outbreak. But of course, many areas that have had record high temperatures this summer have not had outbreaks. So we think temperature may be a permissive factor to promoting West Nile virus outbreak, but certainly isn't the only factor involved. So the end result is we really don't know at this point in time what factors may have contributed to this outbreak, we think it's weather related.”
West Nile virus is transmitted to humans and animals through a mosquito bite. Mosquitoes become infected when they feed on infected birds.
In the United States, most people are infected from June through September, and the number of these infections usually peaks in mid-August, according to the Centers for Disease Control. Seasonal outbreaks often occur in local areas that can vary from year to year. For example, Stanislaus County had at least one human case reported last year in October.
“The peak of West Nile virus epidemics usually occur in mid-August, however it takes a couple of weeks before people get sick, go to the doctor and get diagnosed and then are reported,” Peterson said. “Thus cases now being reported reflect infections from a week or more ago. Thus, we expect many more cases to occur and the risk of West Nile virus infection will probably continue through the end of September.”
Approximately 1 in 5 people who are infected with West Nile virus will develop symptoms such as fever, headache, body aches, joint pains, vomiting, diarrhea, or rash. Less than 1 percent will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues). About 10 percent of people who develop neurologic infection due to West Nile virus will die, according to the CDC. People over 50 years of age and those with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and organ transplants, are at greater risk for serious illness.
There are no medications to treat, or vaccines to prevent, West Nile virus infection. People with milder illnesses typically recover on their own, although symptoms may last for several weeks or months. In the neuroinvasive forms, patients can suffer severe and sometimes long-term symptoms.
The most effective way for individuals to prevent exposure to mosquito bites and West Nile virus is to remember the “Three D’s”:
1. DEFEND – Use an EPA-registered insect repellent with DEET, picaridin, oil of lemon eucalyptus, or IR3535 according to label instructions. Repellents keep the mosquitoes from biting you. DEET can be used safely on infants and children 2 months of age and older.
2. DAWN AND DUSK – Mosquitoes that carry WNV bite in the early morning and evening. It is important to use repellent and wear clothing that reduces the risk of skin exposure to mosquito bites during this time. Make sure your doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens with tears or holes.
3. DRAIN – Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, including buckets, old car tires, and pet bowls. If you have a pond, use mosquito fish (available from your local mosquito and vector control agency) or commercially available products to eliminate mosquito larvae.
Residents can call their local Mosquito Abatement District to report a neglected swimming pools or ornamental ponds or with questions or concerns. In Stanislaus County, north of the Tuolumne River call East Side Mosquito Abatement District at 522-4098. All other residents may call Turlock Mosquito Abatement District at 634-1234. All horse owners are urged to consult their veterinarians about proper and timely West Nile virus vaccinations.
The public can report dead birds to the California Department of Health Services by logging on to http://westnile.ca.gov/cfm/deadbird.cfm or by calling toll-free 1-877-WNV-BIRD (1-877-968-2473).