Register Staff

7-8-2008

Summer is in full swing, which means many more residents and visitors are taking advantage of the area’s outdoor recreation opportunities.
Unfortunately, it also means the threat of West Nile Virus is here.
According to Inyo-Mono Public Health Officer Richard Johnson, the culextarsalis breed of mosquito, the most common West Nile carrier in this area, has been located in southern Mono County.
“This is not an unexpected finding for late June/early July,” Johnson said. “We expect them to be around through the month of July and into August.”
Johnson said he recommends “extra diligence regarding the prevention of mosquito bites,” such as using repellent, wearing long sleeves and pants and limiting outdoor activities at dawn and dusk.

Inyo County Mosquito Abatement Manager Jerry Oser, who predicts the West Nile virus season will pick up in “mid-July” when the insects begin to hatch and breed in vigor in Inyo County, and suggests further that residents be vigilant about keeping an eye out for indicators of West Nile activity.
Since birds are potential carriers of the disease, dead birds should be reported to the Inyo County Mosquito Abatement Program.
Anyone who has located a dead bird and suspects it may be infected is encouraged to call the Inyo County Mosquito Abatement Program at (760) 973-7853.
And with the West Nile virus season on the horizon, following are some of the most common questions associated with the disease, as well as answers provided by Dr. Johnson.

The culextarsalis species of mosquito has been located for the first time this summer by mosquito control officers in Mono County. Now that the species has been identified this year, public health officials are urging residents to use extreme caution in mosquito habitat areas. File photo

Q: What is West Nile virus?
A: West Nile Virus (WNV) is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus which is also found in the United States. The virus can infect humans, birds, mosquitoes, horses and some other mammals
Q: What are West Nile encephalitis, West Nile meningitis and “neuroinvasive disease” and West Nile fever?
A: The most severe type of disease due to a person being infected with West Nile virus is sometimes called “neuroinvasive disease” (WNND) because it affects a person’s nervous system. Specific types of neuroinvasive disease include: West Nile encephalitis, West Nile meningitis or West Nile meningoencephalitis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it. West Nile Fever is another type of illness that can occur in people who become infected with the virus. It is characterized by fever, headache, tiredness, aches and sometimes rash. Although the illness can be as short as a few days, even healthy people have been sick for several weeks.
Q: How long has West Nile virus been in the U.S.?
A: It is not known how long it has been in the U.S., but CDC scientists believe the virus has probably been in the Eastern U.S. since the early summer of 1999, possibly longer. WNV made its first appearance in the Western Hemisphere in New York City in 1999 and quickly spread across the country in the ensuing years, carried by birds and transmitted to humans by mosquitoes. In 2007 the disease struck in 25% of US counties (775 of 3,142) in 44 states, the CDC says. The west-central United States had the heaviest burden of WNND cases, according to the report. North Dakota had the highest incidence, at 7.7 cases per 100,000 residents, followed by South Dakota (6.2), Wyoming (4.6), Montana (4.0), and Colorado (2.2). WNND cases peaked in the first week of August, and 89% of them occurred during July, August, and September.
Q: How common is WNV disease in the United States?
A: The United States had 3,630 reported human cases of WNV disease in 2007. There were 1,227 cases of WNND – the most severe form, with 117 deaths. There were 2,350 reported cases of West Nile fever, and 53 unspecified cases.
Q: Is West Nile virus now established in the Western Hemisphere?
A: During the last four years, there has been a relative stability in the number of reported cases, indicating that it is likely here to stay.
Q: Is the disease seasonal in its occurrence?
A: In the temperate zone of the world (i.e., between latitudes 23.5° and 66.5° north and south), West Nile encephalitis cases occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, West Nile virus can be transmitted year round.
Q: How do people get WNV?
A: Infected Mosquitoes. Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes are WNV carriers (“vectors”) that become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.
• Transfusions, Transplants and Mother-to-Child. All donated blood is checked for WNV before being used. The risk of getting WNV through blood transfusions and organ transplants is very small, and should not prevent people who need surgery from having it. Transmission during pregnancy from mother to baby or transmission to an infant via breastfeeding is extremely rare.
• Not through touching. WNV is not spread through casual contact such as touching or kissing a person with the virus, or by breathing in the virus.
Q: How soon do infected people get sick?
A: People typically develop symptoms from 3-14 days after they are bitten by an infected mosquito.
Q: What are the symptoms of WNV?
A: WNV affects the central nervous system. However, symptoms vary:
• Serious Symptoms in a few People. Less than one percent (about one in 150 people) of individuals infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. WN virus infection can be fatal.
• Milder Symptoms in Some People. Up to 20 percent (about one in five) of the people who become infected will display symptoms which can include fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms generally last for just a few days, although even previously healthy people have been sick for several weeks.
• No Symptoms in Most People. Approximately 80 percent of people (about four out of five) who are infected with WNV will not show any symptoms.
Q: Who is at greatest risk of getting severely ill from WNV?
A: People over the age of 50 have a higher chance of getting sick and are more likely to develop serious symptoms when infected with West Nile virus.
Being outside, especially at dawn or at dusk, increases your risk of being bitten by an infected mosquito. Take precautions to avoid mosquito bites if you spend a lot of time outside, either working or playing.
Risk of transmission through medical procedures is very low. All donated blood is checked for West Nile Virus before being used. The risk of getting WNV though blood transfusions and organ transplants is very small, and should not prevent people who need surgery from having it.
Q: How is WNV infection treated?
A: There is no specific treatment for WNV infection. In cases with milder symptoms, people experience fever and aches that pass on their own. In more severe cases, people may need to go to the hospital where they can receive supportive care including intravenous fluids, help with breathing, and nursing care.
Q: What should I do if I think I have WNV?
A: Milder WNV illness improves without treatment, and people do not necessarily need to seek medical attention for this infection, though they may choose to do so. If you develop symptoms of severe WNV illness, such as unusually severe headaches or confusion, seek medical attention immediately. Pregnant women and nursing mothers are encouraged to talk to their doctor if they develop symptoms that could be WNV.
Q: If you have had WNV, are you immune to further infections?
A: It is thought that once a person has recovered from WNV, they are immune for life to future infections with WNV. This immunity may decrease over time or with health conditions that compromise the immune system.
Q: Can animals get sick from WNV?
A: An infected mosquito can bite any animal, but not all animals will become sick. The disease most often affects birds but may occasionally cause disease in other animals. 
Wild birds serve as the main source of virus for mosquitoes. Infection has been reported in more than 225 bird species. Although many birds that are infected with WNV will not appear ill, WNV infection can cause serious illness and death in some birds. The most severe illnesses are seen among the corvid birds, which include crows, jays, ravens and magpies.
Tree squirrels with West Nile virus can develop neurological symptoms such as uncoordinated movement, paralysis, shaking, or circling and may die.
Like people, most horses bitten by mosquitoes will not become sick with WNV. However, of those that do, clinical signs may include stumbling, circling, hind leg weakness, inability to stand, muscle tremors, and death. A vaccine to prevent West Nile virus is available for horses and horse-owners should consult with a veterinarian about WNV vaccine and other vaccines against mosquito-borne viruses, such as western equine encephalitis. For more information on West Nile Virus and horses, please visit the California Department of Food and Agriculture Web site at http://www.cdfa.ca.gov.
Dogs and cats can be exposed to WNV in the same way as humans. However, these animals are very resistant to WNV and rarely become ill. Concerned pet owners should consult with a veterinarian.
Q: What is happening so far in 2008?
A: So far this year the CDC has reported only 13 WNV cases in seven states, with no deaths. California has reported 3 human cases in 2008: 2 from Stanislaus County, and one from Tulare County, all in the Central Valley. As of July 3, 2008, 20 of 58 counties have reported WNV activity (horses, dead birds, mosquito samples, and sentinel chickens). This is decreased from 24 counties at the same time last year.
Q: What is happening in the Eastern Sierra?
A: There was a single laboratory confirmed case of human WNV infection in Mono County several years ago, and there is some evidence of a single case in Inyo County. This year, as of July 3, 2008, we have not received  notification of any human cases (WNV infections are reportable to the Health Department). Fortunately, most of our mosquitoes are not the right kind to carry the virus efficiently, and our mosquito season is relatively short. Drought conditions also usually mean fewer mosquitoes. 
Q: How can I keep from getting infected?
A: Although a human WNV vaccine is currently being tested, none is available yet. Several vaccines are available and recommended for horses. Consequently, prevention is a matter of protecting oneself from mosquito bites by using insect repellent, keeping skin covered, and avoiding exposure at dawn and dusk, when mosquitoes are most active. Get rid of any standing water on your property. One of the biggest risks in the rest of California is the hundreds of thousands of “green” pools left unattended due to the mortgage crisis.
Q: What should I do when I find a dead bird?
A: While surveillance for WNV in birds focuses mainly on crows, jays and magpies, the virus has been found in 321 bird species since 1999. Therefore, if you find a dead bird without obvious signs of trauma, you are asked to report it to 1-877-WNV-BIRD. Your report will be recorded, and someone may contact you so that the bird can be tested. See www.westnile.ca.gov.