Invasive Mosquito Problem in California, Major Cause for Concern

The Dengue virus is a leading cause of death and illness in the subtropics and tropics. Up to 400 million individuals are infected with the virus on an annual basis. Dengue is the result of one of four viruses for which the primary method of transmission is mosquito bites. The current presence of Aedes albopictus and Aedes aegypti mosquitoes in California poses a serious threat to residents who may come in contact with the insects and subsequently contract the Dengue virus. A vaccine has not yet been invented to prevent such infections, and therefore avoiding mosquito bites and preparing for a potential mosquito invasion are considered the most effective ways to prevent a Dengue outbreak.

Concerned Californians

Two distinct, non-native mosquito species have recently been discovered wreaking havoc in several major cities in California, and their presence could potentially spread to additional areas throughout the state. The specific strains are the Asian tiger mosquito, for which the technical name is Aedes albopictus, and the yellow fever mosquito, referred by scientists as the Aedes aegypti. Unlike the majority of mosquito species that bite in the evening and early morning, Aedes albopictus and Aedes aegypti launch their attacks during the day. Both species have a similar appearance. They are small, black insects with white stripes on their legs and back and can lay eggs in any location where water is present.

As previously mentioned, both species of mosquitoes can potentially transmit several viruses to humans and animals. In addition to the Dengue virus, they may also transmit yellow fever and a virus called chikungunya, which was once only present in Africa and the Middle East. The Centers for Disease Control and Prevention have yet to receive a report of any of these viruses within the state of California; however, thousands of individuals are affected with them in different regions of the world, including Asia, the Caribbean, Central and South America, and Mexico. Even more disturbing is documented cases of the virus in Hawaii. Because both species of mosquitoes have been discovered in California, residents and workers at the California Department of Health are concerned about a potential outbreak in the state.

Understanding Dengue Fever

Also called break bone fever, symptoms of the Dengue virus include muscle and joint pain, headache, high fever and a skin rash similar to that seen with measles outbreaks. In a small percentage of cases, the virus develops into dengue hemorrhagic fever–DHF–which results in blood plasma leakage, low levels of blood platelets, bleeding and Dengue shock syndrome–characterized by dangerously low blood.

Hawaii

Since the first outbreak in 2011, the Hawaii Department of Health is currently investigating locally-acquired cases of Dengue from various areas around the state. Although Dengue is not native to Hawaii, it is transmitted to the island chain from other places in the world by infected travelers. In 2015, for the first time since the 2011, locally-acquired dengue virus cases were reported.

As of November 18, 2015, the state of Hawaii has confirmed 72 cases of Dengue virus, 62 of which were diagnosed in Hawaiian residents and ten in visitors. Of the confirmed cases, 53 are adults and 19, children under the age of eighteen. Thirty-one potential cases were dismissed for failure to meet case criteria or for negative results following specialized testing.

Since initiating the current investigation on the big Island of Hawaii Island, one imported case of Dengue fever case was reported, as well. The victim was a resident of the Island of Oahu.

The Hawaii Department of Health is continuously monitoring for cases of the infection on all islands and regularly uses pest control establishments to perform mosquito site evaluation and extermination as deemed necessary.

Some residents on the West Coast are concerned that California may be “the next Hawaii,” as individuals frequently travel to the Hawaiian Islands for leisure or business purposes. Although the government is likely attempting to avoid a panic, the very serious risk of Dengue virus cannot be overlooked. For this reason, it is important for residents of the state to understand that they may be invaded by such mosquitoes at any time and take adequate measures to protect themselves from the disease.

Treatment

There is no specific drug or therapy used to treat Dengue infections, and treatment is supportive rather than curative. In most cases of mild or moderate Dengue fever, doctors prescribe intravenous fluids, rest, medications such as acetaminophen, and more rarely, blood transfusions. Nonsteroidal anti-inflammatory medications such as aspirin, naproxen sodium and ibuprofen should be avoided if the virus is present.

In addition to eliminating the disease carrying mosquitoes, research is constantly underway to discover a vaccine for the virus, as well as develop drugs to directly target Dengue and similar viruses. Patients who test positive for the virus must be carefully monitored for DHF, and if it is suspected that a person is suffering from this complication, hospitalization and fluid replacement therapy must be pursued at once. When an infection is underway, early recognition and immediate supportive therapy substantially lower the chances of death or medical complications.

Prevention

Limiting exposure to mosquito bites and reducing the number of mosquitoes in California cities is the best way to prevent an epidemic and Californians should make every effort to protect themselves from the disease. When outdoors or in areas where mosquitoes are known to thrive, residents of California should use generous amounts of insect repellent, wear pants and long sleeves whenever possible, or stay in areas with door and window screens or where air conditioning is used. It is not yet known whether or not an invasion will occur, but residents of California are advised to err on the side of caution with regard to mosquito-borne illnesses.

**Please call the District if you have any day biting mosquitoes. It is a public service that is covered through property taxes.**