California recorded its first fatality of the year from the West Nile virus, just as new cases have been reported in Stanislaus County.
The fatality was that of an 88-year-old woman from Kern County, the California Department of Public Health announced Friday.
"This unfortunate death reminds us that we must protect ourselves from mosquito bites to prevent West Nile virus and other mosquito born infections," said Dr. Ron Chapman, director of the California Department of Public Health.
The state's West Nile virus website, which tracks cases with the CDPH, is reporting 11 human cases of West Nile virus in six counties.
Stanislaus County has four reported human cases, two of which were reported this week.
"We have not had that many cases in July in about four years," said Stanislaus County Public Health Officer Dr. John Walker. "It is an upward trend that concerns us. Unfortunately, we are anticipating a bad season."
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, said Monica Patterson, a vector biologist with the Turlock Mosquito Abatement District.
Many factors impact when and where outbreaks occur, such as weather, numbers of mosquitoes that spread the virus, and human behavior.
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. In more severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.
The four people in Stanislaus County sickened with the virus range in age from 6 years to 65 years. The two earlier reported cases have been diagnosed as neuroinvasive, which is the most severe form of the virus.
"We are tending to see more of the severe forms of the virus," Walker said. "Typically we would expect 5 to 20 percent presenting with the more severe form, but we are already at 50 percent."
The other two cases in Stanislaus County have developed West Nile fever, but have not required hospitalization.
Stanislaus County has also recorded 24 dead birds and one horse with the virus. The horse had to be euthanized.
Health officials and mosquito abatement districts are both reporting an increase in virus activity this year - at both the local and national level.
Last year at this time the virus was present in 18 California counties with seven human cases. Currently, 27 California counties have recorded West Nile virus activity and there are 11 human cases.
Nationally, 42 states have reported West Nile virus infections in people, birds, or mosquitoes. A total of 241 cases of West Nile virus disease, including four deaths, have been reported to the CDC. This is the highest number of cases reported through the end of July since 2004. Almost 80 percent of the cases have been reported from three states, Texas, Mississippi, and Oklahoma.
Chapman said California residents are very good at protecting themselves from mosquito bites for planned events like camping, however, tend to have a false sense of security in their own backyards. The most effective way for individuals to prevent exposure to mosquito bites and West Nile virus is to remember the "Three Ds":
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.
"People are doing a good job of helping identify area where mosquitoes are at and reporting dead birds, which gives us a clue to the presence of the virus," Patterson said.
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).