Zika Virus In The US

29 07 2016

We are all familiar with the word “Zika” because of the infections in Brazil.

The Florida Health Department and state officials have announced that they have identified four cases of Zika virus infection that were most likely transmitted locally. These cases are in Wynwood, an area just north of Miami

This is probably the first time that mosquito-borne transmission of Zika virus has happened in the continental US.mosquito

The CDC and Florida are saying “likely” and “probably” because, although they cannot yet prove these individuals were bitten by infected mosquitoes, there seems to be no other method of transmission in these cases, and the mosquito that carries the virus does live in the area.

However, this does not mean that the Zika virus will become widespread in the US.

The Zika virus is transmitted a few ways. The most common way for people to get the Zika virus is to be bitten by an infected Aedes species mosquito (Ae. aegypti and Ae. Albopictus).

This mosquito doesn’t like the climate in all parts of the US. Much of the northern area will not be at risk from this mode of transmission.

Also, this mosquito never travels more than 150 meters its entire life. That’s less than 1/10th of a mile. It usually travels far less than that distance.

The West Nile virus, on the other hand, was able to pretty much cover the US because the virus can be transmitted from an infected mosquito to a bird, which then flies off quite a distance before landing and getting bitten by a different mosquito, which then becomes infected. That mosquito, in turn, bites another bird. This cycle hopscotches its way across the US, spreading disease from bird to mosquito to bird to mosquito.

The mosquitoes also infect humans and other mammals with West Nile virus.

The mosquitoes that carry the Zika virus don’t work that way. They prefer to only bite humans.

Another reason the Zika virus will probably not explode across the US is because where the mosquito lives, people use screens across their windows and doorways, and they use air conditioning. It’s more difficult for the mosquito to get into the houses.

There are other ways for the Zika virus to be transmitted.

An infected pregnant woman can pass it to her fetus during pregnancy or around the time of birth.

An infected individual can pass the virus through sex with their partner. An infected person may or may not be symptomatic—they can still transmit the virus. It appears that four out of five infections are asymptomatic. One cannot assume that a person is virus-free just because they don’t seem to be sick.

An infected person may donate blood and the virus can then be passed through blood transfusions.

This virus is under a lot of scrutiny. New methods of transmission may be identified, but these are the primary methods at this time.

Now we have an idea of how it’s transmitted. What can we do about it?

Where pockets of infection have occurred, the state and local authorities have started aggressive mosquito control, including spraying and going door to door to alert residents to standing water. Mosquitoes love to lay eggs in standing water—making sure there is none helps to control the mosquito population.

We all need to prevent mosquito bites by using insect repellent containing DEET, wearing long sleeves and pants, and staying indoors unless covered and protected. This is particularly true for pregnant women, and for those living in areas where these mosquitoes are common.

For up-to-date info on Zika virus, visit http://www.cdc.gov/zika/





Summer + Mosquitoes = Dengue Fever?

13 05 2014

The dengue fever virus is the most common virus that mosquitoes transmit and infects about 100 million people worldwide every year, killing about 25,000. In spite of this frequency, though, the United States, with the exception of Puerto Rico, has been mostly dengue-free for decades—until 2009.

image by infidelic

That year, a woman in New York turned up with a dengue infection, having just returned from a trip to the Florida Keys. Her case was the first of a handful that led public officials to conduct a survey of the Key West population. To their shock, they found that about 5% of residents, or about 1000 people, showed evidence of dengue exposure in 2009.

The mosquito that carries the virus occurs in warm areas of the country, including Florida and Texas, and indeed, isolated cases of dengue have cropped up a few times since the 1980s along the Texas–Mexico border. But the cases in 2009 and more in 2010 have authorities concerned that dengue now has achieved an intractable foothold on the continental United States.

Work on a vaccine against dengue is ongoing, but in the meantime, the only preventive is to avoid the bug that carries the virus: the mosquito.

Wearing repellent when in areas where they occur is one tactic. Another is removing breeding places, such as any containers with standing water. The precautions apply wherever you’re going, whether to areas where dengue is already endemic or where it is emerging. The CDC provides regular updates for travelers, including a page specific to the Florida cases.

Dengue fever can hit hard or harder, depending on the symptom severity. The “mild” version of the disease can involve a high fever, a rash, severe headache and pain behind the eyes, and nausea and vomiting.  Given that these symptoms are largely nonspecific, if you see your doctor about them and have traveled in a place where dengue fever occurs, be sure to mention it. A more severe form of dengue fever is dengue hemorrhagic fever, which begins much like the “mild” form but then progresses to symptoms that can include nosebleed and signs of bleeding under the skin, known as petechiae.  This form of dengue can be fatal.

The most severe manifestation of the disease, dengue shock syndrome, includes the symptoms of the milder forms along with severe abdominal pain, disorientation, heavy bleeding, and the sudden drop in blood pressure that signals deadly shock.  Onset is typically four to seven days after exposure, and the mild form usually lasts only a week, while the more severe forms can involve either a progressive worsening or a sudden worsening following an apparent improvement.

Oddly enough, having dengue fever once does not mean you’re safe from it. Indeed, some studies indicate that a second bout of dengue fever often can be worse than the first, with a greater risk of progressing to the hemorrhagic form.