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Viral Diseases

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Selected viral diseases considered below are those known to be present in the El Paso/Juarez Region or have high potential to reach the region under the conditions of climate change. Of those listed below, West Nile virus is known to occur locally.

Viral diseases, their vectors, and their reservoirs, El Paso Region
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Chikungunya

Currently (June 2014), chikungunya in the U.S. and Mexico appears to be limited to imported cases—cases where the virus was picked up in the Old World or in the Caribbean (or potentially in northeastern South America). The presence in the Caribbean is recent, the first cases being recognized in 2013. Local transmission (meaning that the virus is being transmitted locally rather than only appearing in people who were infected elsewhere) is prevalent in the Caribbean, with the estimate of the number of people infected running to over 180,000 as of late June 2014. Since Aedes aegypti and Aedes albopictus), the primary species spreading the virus, are common in North America, eventually local transmission is expected in the U.S. and Mexico.

Transmission

Chikungunya virus is transmitted to people through mosquito bites. Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites. It is most often spread to people by Aedes aegypti and Aedes albopictus mosquitoes. These are the same mosquitoes that transmit dengue virus. They bite mostly during the daytime.

Symptoms

The symptoms of chikungunya are similar to those of dengue, another disease spread by mosquitoes. Most people infected with chikungunya virus will develop some symptoms. Symptoms usually begin 3–7 days after being bitten by an infected mosquito. The most common symptoms are fever and joint pain. Other symptoms may include headache, muscle pain, joint swelling, or rash. Chikungunya disease does not often result in death, but the symptoms can be severe and disabling. Most patients feel better within a week. In some people, the joint pain may persist for months. People at risk for more severe disease include newborns infected around the time of birth, older adults (≥65 years), and people with medical conditions such as high blood pressure, diabetes, or heart disease. Once a person has been infected, he or she is likely to be protected from future infections.

There is no medicine to treat chikungunya virus infection or disease. The usual recommendations are to get plenty of rest, drink fluids to prevent dehydration, and take medicines, such as ibuprofen, naproxen, acetaminophen, or paracetamol, to relieve fever and pain.

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Dengue

As recently as the 1940s, dengue outbreaks in the U.S. occurred as far north as Boston. At present, however, occurrence in the U.S. is limited largely to cases where the virus was picked up outside of the country. However, with looming climatic change, the current widespread occurrence of the Aedes vectors, and the pool of susceptible humans, outbreaks can be expected in the future.

Transmission

Dengue is transmitted between people by the mosquitoes Aedes aegypti and Aedes albopictus, which are found throughout the world. Insects that transmit disease are vectors. Symptoms of infection usually begin 4 - 7 days after the mosquito bite and typically last 3 - 10 days. In order for transmission to occur the mosquito must feed on a person during a 5-day period when large amounts of virus are in the blood; this period usually begins a little before the person become symptomatic. Some people never have significant symptoms but can still infect mosquitoes. After entering the mosquito in the blood meal, the virus requires an additional 8-12 days incubation before it can then be transmitted to another human. The mosquito remains infected for the remainder of its life, which might be days or a few weeks.

Although Aedes mosquitoes are common in the southern U.S., dengue is endemic in northern Mexico, and the U.S. population has no immunity, the lack of dengue transmission in the continental U.S. is primarily because contact between people and the vectors is too infrequent to sustain transmission.

Symptoms

Dengue


Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.

Watch for warning signs as temperature declines 3 to 7 days after symptoms began. Go IMMEDIATELY to an emergency room or the closest health care provider if any of the following warning signs appear:

Dengue Hemorrhagic Fever

Dengue hemorrhagic fever is characterized by a fever that lasts from 2 to 7 days, with general signs and symptoms consistent with dengue fever. When the fever declines, warning signs may develop. This marks the beginning of a 24 to 48 hour period when the smallest blood vessels (capillaries) become excessively permeable ("leaky"), allowing the fluid component to escape from the blood vessels into the peritoneum (causing ascites) and pleural cavity (leading to pleural effusions). This may lead to failure of the circulatory system and shock, and possibly death without prompt, appropriate treatment. In addition, the patient has a low platelet count and hemorrhagic manifestations, tendency to bruise easily or have other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding.

Treatment

There is no specific medication for treatment of a dengue infection. Persons who think they have dengue should use analgesics (pain relievers) with acetaminophen and avoid those containing ibuprofen, naproxen, aspirin, or aspirin-containing drugs. They should also rest, drink plenty of fluids to prevent dehydration, avoid mosquito bites while febrile and consult a physician.

As with dengue, there is no specific medication for Dengue hemorrhagic fever. If a clinical diagnosis is made early, a health care provider can effectively treat Dengue hemorrhagic fever using fluid replacement therapy. Adequately management of Dengue hemorrhagic fever generally requires hospitalization.

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West Nile Virus

The Greater El Paso/Juarez Region regularly records cases of West Nile, including a few deaths, usually of persons whose health already is compromised. According to the El Paso Times, 32 cases were reported for El Paso in 2012, with 6 deaths. The Texas Department of Health Services reported 16 cases in El Paso County in 2013, including 2 deaths; El Paso and Dallas counties were tied for the most cases per county in Texas.

Transmission

Over 60 species of mosquitoes have been documented as carrying West Nile virus. Although relatively few of these species occur in the region, the most prevalent species are on the list.

Transmission Cycle

As the Centers for Disease Control illustration above indicates, Humans can contract West Nile Fever, but do not pass it on.

The information below on symptoms and treatment come from the CDC.

Symptoms

Seventy to eighty percent of people who become infected with West Nile virus do not develop any symptoms. About 20% of people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Less than 1% of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues). The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis. People with certain medical conditions, such as cancer, diabetes, hypertension and kidney disease are also at greater risk for serious illness. Recovery from severe disease may take several weeks or months. Some of the neurologic effects may be permanent. About 10 % of people who develop neurologic infection due to West Nile virus will die.

Treatment

No vaccine or specific antiviral treatments for West Nile virus infection are available. Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms. In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.


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