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.





Airplane Cabins and Your Health

30 08 2012

Do you remember SARS (Severe Acute Respiratory Syndrome)? It popped up in China in 2002 and spread to more than 25 countries before we could blink.

PKIDs landed a group of disease prevention educators in China just as the world became aware of this outbreak that would rapidly become an epidemic. It was coincidence, of course. The trip had been planned for months.

But, our proximity to the SARS outbreak was a reminder to us of how efficient air travel is at spreading germs.

In 2009, there were 2.5 billion airline passengers and that number is expected to increase to 3.3 billion by 2014. That’s a lot of sneezing, coughing, and just plain touching of armrests, overheads, and other surfaces going on in small spaces.

Dr. Alexandra Mangili and Dr. Mark Gendreau wrote a piece for the Lancet in 2005 that talks about the mechanics of disease transmission in an airplane. It’s very good, if you have a few minutes to read it.

They explain air flow patterns and how much air is recirculated (50% and that’s through filters). Turns out, air does not flow the length of the plane, but rather in sections or pockets along the width of the plane. Still an efficient method of disease transmission for airborne and large droplet transmission, but not the only way germs are spread onboard.

According to the article, the most common infections on aircraft have been via the fecal-oral route through contaminated food, although that has diminished in the last few years, possibly due to prepackaged food products and more care in the prepping and handling of food.

Mosquitos, a common vector for diseases such as dengue and malaria, often hitch rides on airplanes. Mangili and Gendreau point out that, “Many cases of malaria occurring in and around airports all over the world in people who had not travelled to endemic areas, known as airport malaria, is evidence that malaria-carrying mosquitoes can be imported on aircraft.”

The cabins of airplanes cannot be thoroughly disinfected between flights. Many times, a plane lands, passengers disembark, and more passengers are seated within 30 minutes. Think of all the droplets of goo left behind that the cleaning crew cannot remove, and the many surfaces that can’t be disinfected.

Keeping one’s hands clean throughout the flight will go a long way toward preventing transmission, and staying up-to-date on your vaccinations for your home country and your destination. As for masks, the authors say, “Although masks play a crucial part in infection control in health care settings, their use is unproven in disease control within the aircraft cabin.” But they do recommend masking and isolating someone suspected of having SARS.

The CDC has quite a bit more to say about air travel and travelers’ health in general, if you’re looking for more details.

How do you prevent infections during air travel? What do you do to protect yourself? We’d love to hear! Please share your tips in the comment section.

By Trish Parnell
Image courtesy of WHO





Those Rotten Mosquitos!

6 08 2012

West Nile virus is busy this year, with 241 cases and four deaths reported.

Mosquitos are the carriers of this disease, and we all know the mosquito population has exploded this summer. It is possible to transmit West Nile virus (WNV) in other ways, such as through blood transfusions, organ transplants, breastfeeding, or even during pregnancy from mother to baby, but the risk for those types of transmissions is small.

No one wants WNV, so the first thing to do is prevent mosquito bites.

Use insect repellent, and reapply it periodically – read the directions on the can.

Look around your property – if there’s any standing water, drain it. Mosquitos love to breed in still waters.

Mosquitos were getting in our house in the evenings. After a couple of hours of investigation, we discovered a gap in a screen where they were getting through. Check every door and window in your home for openings.

There is no vaccine for humans, but research is ongoing.

Most people who are infected with WNV experience no symptoms, but for some, infection can cause fever, headache, nausea, coma, paralysis and other serious problems.

There is no treatment specific to WNV. If you become infected, your symptoms will be treated.

Be aware that mosquitos carry more than WNV. They also carry and transmit dengue, various viral diseases that cause encephalitis, malaria, yellow fever, and Rift Valley fever.

Contact your city or county to find out what they’re doing to reduce the mosquito population. If they’re not doing enough, rally your neighbors to add their voices to yours in asking that action be taken.

By Trish Parnell

Image courtesy of LoloTahiti