Credit CDC
# 7507
It’s been a few months since we last looked at Dengue fever activity in Puerto Rico - and while nowhere near the intensity of the 2010 epidemic (see red line in chart below) - the summer of 2013 is running well above the epidemic level (see chart above).
This epidemic ended in December of 2010, but before it was quashed it had infected more than 21,000 people, killing 31 (see MMWR: Dengue Epidemic In Puerto Rico).
The following year (2011) was an average or slightly below average year for Dengue in Puerto Rico, but by the middle of last summer (see Dengue Above Epidemic Threshold In Puerto Rico) dengue numbers began to rise in Puerto Rico.
In October of 2012 Health Secretary Lorenzo Gonzalez of the Puerto Rico Health Department once again declared a Dengue epidemic on the island (PDF Link – in Spanish), stating that at least six people have died, two of them being children (see Puerto Rico Declares Dengue Epidemic).
While mosquitoes exist year-round in Puerto Rico, the end of the rainy season (which normally runs April-Nov) usually signals a drop in their numbers. But as you can see by the chart at the top of this page, those numbers never dropped below the epidemic level during the spring.
Which brings us to the most recent (week 25) Dengue Surveillance report from the CDC. (Note: Surveillance figures typically run about 3 weeks behind to give time to compile and analyze the numbers).
The true burden of the disease is likely much higher than these numbers reflect, as often the first infection produces only mild symptoms, and may even be completely asymptomatic.
This from the CDC’s Clinical Guidance on Dengue
Asymptomatic Infection: As many as one half of all dengue infected individuals are asymptomatic, that is, they have no clinical signs or symptoms of disease.
Undifferentiated Fever: The first clinical course is a relatively benign scenario where the patient experiences fever with mild non-specific symptoms that can mimic any number of other acute febrile illnesses. They do not meet case definition criteria for DF. The non-specific presentation of symptoms make positive diagnosis difficult based on physical exam and routine tests alone. For the majority of these patients, unless dengue diagnostic serological or molecular testing is performed, the diagnosis will remain unknown. These patients are typically young children or those experiencing their first infection, and they recover fully without need for hospital care.
Dengue Fever with or without hemorrhage: The second clinical presentation occurs when a patient develops DF with or without hemorrhage. These patients are typically older children or adults and they present with two to seven days of high fever (occasionally biphasic) and two or more of the following symptoms: severe headache, retro-orbital eye pain, myalgias, arthralgias, a diffuse erythematous maculo-papular rash, and mild hemorrhagic manifestation.
There are 4 different serotypes of the Dengue Fever virus (Puerto Rico is reporting types DENV1 & DENV4), so a person can easily become infected several times over their lifetime.
One of the concerns is that travelers visiting dengue endemic areas may carry the virus back home with them, and `seed’ local mosquito populations with the virus.
The CDC’s MMWR in a report in May of 2010 on Locally Acquired Dengue in Key West, had this to say:
Cases of dengue in returning U.S. travelers have increased steadily during the past 20 years (8). Dengue is now the leading cause of acute febrile illness in U.S. travelers returning from the Caribbean, South America, and Asia (9).
Many of these travelers are still viremic upon return to the United States and potentially capable of introducing dengue virus into a community with competent mosquito vectors.
While Florida has yet to report its first locally acquired dengue case of 2013, the latest Arbovirus Surveillance report (July 13th) shows 43 imported cases of Dengue since the first of the year.
Imported Dengue:
Forty-three cases of dengue with onset in 2013 have been reported in individuals with travel history to a dengue endemic country in the two weeks prior to onset. Countries of origin were: Angola, Barbados, Bolivia, Brazil (3), The Caribbean, Columbia (3), Costa Rica, Dominican Republic (4), Haiti (2), Honduras, Indonesia, Jamaica (4), Nigeria, Panama, Philippines, Puerto Rico (16) and Saint Martin.
Counties reporting cases were: Brevard, Broward (4), Clay, Duval, Indian River, Lee, Miami-Dade (14), Orange (9), Osceola (3), Palm Beach (6), St. Lucie and Volusia. Six of the cases were reported in non-Florida residents.
The odds of contracting Dengue, or any other mosquito transmitted diseases, are actually pretty low.
But with no vaccine, and the potential for serious illness, it makes sense to take reasonable precautions whenever you are around mosquitoes (and not just in Dengue endemic areas).
Those who travel to, or live in areas where mosquitoes are present are reminded that to follow the `5 D’s’:
