Over the next few decades, if we don't take steps to protect ourselves, we could see more cases of dengue fever - a mosquito-borne viral disease -- appearing more frequently, in more places around the world. As we've learned from recent experiences with West Nile virus and other vector-borne infectious diseases, many factors play into the spread of these illnesses. Disease-carrying mosquitoes are one such factor, and global warming can impact mosquitoes in many ways.
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Say you work in a health clinic. You're starting to hear more about dengue fever (also known as "breakbone fever" because of its extremely painful symptoms), and you just read about it in On Earth magazine's Fall 2009 cover story, or in NRDC's recent report Fever Pitch about the disease and its spread. But what are the symptoms of dengue fever that you should look for when patients come back ill from travel abroad? What do you do to help them, and where do you go if you have questions?
If you see a patient who has a fever, and they've traveled to a tropical area within two weeks of the beginning of their symptoms, you should consider dengue fever in your differential diagnosis. The symptoms in the classic "dengue triad" include high fever and chills; severe headaches, eye pain, bone, joint, and muscle pain (hence the nickname "breakbone fever"); and a rash on the arms, legs, and torso, with swelling and redness of the hands and feet. The rash sometimes doesn't appear until several days after the fever starts, so the absence of a rash shouldn't exclude dengue.
Commercial lab tests are more available here in the US for a serological diagnosis, but the results need to be interpreted carefully since anti-dengue antibodies are non-specific among the flaviviruses, including West Nile and St. Louis encephalitis. According to the Centers for Disease Control and Prevention (CDC), when dengue fever is suspected, healthcare providers should send a blood specimen, associated clinical information (case form), and a brief travel history to the state public health laboratory with a request that the specimen be tested for dengue there or at the CDC's Dengue Branch in San Juan, Puerto Rico. If that's not possible, contact the (CDC). We've heard dengue may now be in the process of becoming a nationally notifiable disease, which is great news.
You can get more information designed especially for clinicians from the CDC website. An unequivocal diagnosis of infection requires lab confirmation, either by isolating the virus or detecting specific antibodies. Laboratories that can perform these tests may not be nearby, and specimens require special handling.
Treatment for suspected infections should include bedrest and plenty of fluids. To manage the pain and fever, acetaminophen can be given - but avoid aspirin and other non-steroidal anti-inflammatory medications. In rare cases, people -- usually children -- will need to be treated in the hospital for dengue fever. If that happens, doctors should draw blood samples while the patient is sick and again after recovery to confirm the dengue fever diagnosis.
In general, the prognosis of dengue fever is excellent, however people who have previously had the disease and are re-infected with a different strain can experience a complication: dengue hemorrhagic fever (DHF). Symptoms of DHF include peteciae and purpura, along with bleeding. Patients with these symptoms will require hospitalization and supportive care to prevent shock and death.
I recently spent some time traveling in India, where dengue fever outbreaks have become a tremendous public health issue. Millions of impoverished people there live in close contact with mosquito breeding areas. The nation is aiming to ramp up its lab capacity, case reporting and centralized monitoring systems, which will improve infectious disease preparedness. I took personal precautions to keep mosquitoes away while there and had no problems at all - but watched for symptoms after I returned home, since it's possible to be bitten and not realize it. (No symptoms appeared, and I enjoyed an amazing trip!)
This Saturday October 17th at 7:00 pm on many Planet Green network stations, Focus Earth with Bob Woodruff will air a segment titled "Outbreak." In it, you'll be able to see first-hand what dengue fever means for people living in the Texas-Mexico border area, and what's being done to address this health concern in the border community. I was interviewed for the show, along with dengue experts and people who live and work in Brownsville, Texas, and Matamoros, Mexico.
If you're a health care professional, encourage your patients not to mess around with a fever of unknown origin after they return home from travels abroad. It's good advice to, "Tell friends about travels, but tell doctors about symptoms."