Cases of dengue fever nearly doubled last year in United States

U.S. residents returning from travel in the tropics bring the disease home with them. And the mosquito that transmits the disease is finding the U.S. quite hospitable.

[Increasing numbers] [Common symptoms]
[Awareness important] [When to consider dengue]

[Your turn]

January 1997

--- Most dengue cases result in mild symptoms such as rash; but for some, infection can be fatal.

ATLANTA — The incidence of dengue fever substantially increased last year in the United States as more travelers returned home from tropical regions where they may have acquired the disease, according to a recent report by the Centers for Disease Control and Prevention (CDC).

Dengue fever is an acute disease caused by any of four mosquito-transmitted virus serotypes (DEN-1, DEN-2, DEN-3, DEN-4), and is transmitted in the Americas by Aedes aegypti mosquitoes. Although the disease was nearly eradicated from the region in the 1960s, this species is now present in most tropical areas of the Americas and is present year-round in the most southern areas of Florida and Texas. A small focus also exists on the island of Molokai, Hawaii.

Because the disease is endemic in most tropical areas of the world, it can occur in U.S. residents returning from such areas, the report stated.

Increasing numbers

In 1995, dengue outbreaks were reported from many countries in Central America and the Caribbean. As a result, the number of laboratory-diagnosed cases reported to the CDC in 1995 was 86, nearly doubling the average number of 45 cases between 1987 and 1994, according to the report.

Serum samples from 441 people (from 31 states and the District of Columbia) who suspected dengue with onset in 1995 were submitted to the CDC for diagnostic testing. Of these, 79 (18%) cases from 21 states were serologically or virologically diagnosed as dengue. Seven additional cases with laboratory-positive dengue were re ported by the Texas Department of Health.

Of the 281 suspected cases reported from Texas, most (71%) resulted from intensified surveillance by the Texas health department because of an epidemic of dengue in the adjoining state of Tamaulipas, Mexico. Cases of dengue were also diagnosed among a group of disaster-relief workers from Oregon who traveled to St. Thomas, U.S. Virgin Islands, and travelers to Tortola, British Virgin Islands.

Common symptoms

Most cases of dengue are characterized by mild manifestations like the sudden onset of fever, headache, myalgias, rash, nausea and vomiting, but infection in some people can result in the more severe forms of the disease called dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS).

DHF results is fever, decreased platelet count, hemorrhagic manifestations and a leaky capillary syndrome. DSS causes similar symptoms to DHF plus hypotension or narrow pulse pressure. The fatality rate for patients with DSS can be as high as 44%, compared with 1%-2% for patients with appropriately treated DHF, the report stated.

Awareness important

--- The A. albopictus mosquito can also transmit dengue.

The cases among disaster-relief workers and people who traveled to Tortola underscore the importance of prevention measures for susceptible people who travel to areas with endemic disease. These measures include avoiding of exposure to mosquitoes. Although mosquito activity is greatest in the early morning and in the late afternoon, mosquitoes may feed at any time during the day, especially indoors, in shady areas, or during overcast periods. Mosquitoes may be present in dark areas like closets, bathrooms, behind curtains and under beds, the report stated.

When to consider dengue

Health care providers should consider dengue in the differential diagnosis for all patients who have fever and a recent history of travel to tropical areas. Only acetaminophen products are recommended for management of fever because of the anticoagulant properties of acetylsalicylic acid.

Of the 86 people with laboratory-confirmed dengue, 44 (51%) were female. Ages were reported for 54 people and ranged from 1 year to 73 years. The virus serotype (DEN-1, DEN-2, DEN-3) was identified in five cases. Based on travel histories available for 81 people, infections probably oc curred in the Caribbean islands (48), Mexico and Central America (24), Asia (5) and South America (3) and Africa (1), according to the report.

For more information:

CDC: Imported Dengue. MMWR. 1996;45:988-991.

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