The patient’s symptoms following a one-week tour across Costa Rica indicated a viral illness. But which one?

A 38-year-old man presented to the primary-care clinic complaining of persistent fever, generalized pain, and fatigue. Five days earlier, he had been diagnosed with a flulike viral illness and instructed to increase fluids and take antipyretics as needed. He described the pain as deep in his bones and muscles and rated it a 9 on a 10-point scale. He also noted a severe headache confined to the frontal and retro-orbital area but reported no sinus congestion, cough, sore throat, or dysphagia. He did not complain of abdominal pain, nausea, vomiting, chills, diaphoresis, neck pain, photophobia, or rash. He had no significant past medical history and was taking no medications.

Vital signs included a 101°F oral temperature, BP 96/58 mm Hg, and pulse 82 beats per minute. The patient’s neck was supple with no adenopathy. His conjunctivae were without injection, sinuses were nontender, and oral mucosa was moist without exudate.

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Hypopigmented macules with surrounding erythema were noted on the forearms. No other lesions or rash was observed. His abdomen was soft and nontender.

Further questioning revealed that the patient had recently spent one week in Costa Rica. While there, he had spent time in both urban and rural areas. He drank only bottled water but took no precautions against insect exposure. The patient had no health insurance and refused blood work. He was instructed to avoid aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), increase his fluid intake, and contact the clinic daily. Acetaminophen was allowed for symptomatic relief. Over the next few days, the fever and pains began to resolve. No further symptoms developed.

AnalysisBased on this man’s symptoms and examination, the most likely diagnoses included dengue fever, meningitis, malaria, and Rocky Mountain spotted fever (RMSF).


Meningitis typically causes fever and headache, but patients also note nuchal rigidity and commonly complain of photophobia. Aseptic meningitis may cause a morbilliform rash along with pharyngitis and adenopathy. Meningococcal meningitis is associated with systemic toxicity and a diffuse maculopapular rash.

Malaria presents with shivering and shaking chills followed by high fever, tachycardia, diaphoresis, and an abrupt drop in body temperature. This pattern typically repeats itself cyclically but was not present in our patient.

RMSF is endemic to the southeastern and south-central United States. The triad of fever, tick exposure, and rash are characteristic. The rash is maculopapular and then petechial, beginning on the wrists and ankles and spreading centrally. Patients commonly complain of chills, headache, conjunctival injection, cough, myalgias, and malaise.


The most likely diagnosis was dengue fever. Dengue fever is caused by a member of the Flavivirus family (Figure 1). There are four distinct serotypes; exposure to one serotype confers lifelong immunity to that serotype only. It is transmitted through the bite of the Aedes mosquito (Figure 2), which can be found in increasing numbers in many parts of the world but is most prevalent in the tropics and subtropics and widespread in the Caribbean basin. Infections have been increasing over the past two decades, especially in the Americas since cessation of the Pan American Health Organization mosquito-control programs. Sporadic cases have been recorded in Texas and other parts of the southern United States. The World Health Organization estimates 50 million cases occur worldwide each year, 600,000 of those in the Americas.

Most infections are mild and self-limited. The patient develops fever with relative bradycardia, pain, headache, and mild rash 3-14 days after a mosquito bite. Diagnosis can be confirmed through serology. Although weakness and fatigue may persist for weeks, mortality is less than 1%.

A subset of patients (<10%) develops dengue hemorrhagic fever (DHF), characterized by vascular leakage leading to hemorrhagic complications and disseminated intravascular coagulation. Severe DHF leads to dengue shock syndrome, circulatory collapse, and death. Use of aspirin or NSAIDs may increase the risk of developing DHF. Warning signs are abdominal pain, protracted vomiting, hypothermia, and change in mental status. Aggressive fluid therapy and supportive care are the only options for treatment. Antivirals are not effective. Mortality can reach 50% in untreated patients.

Although dengue fever has been recognized for more than 200 years, it is considered an emerging infection because of the increasing number of cases and its spread to all areas of the globe.

Urbanization in areas of endemicity, absence of proactive public-health efforts (including water protection and mosquito control), global travel, and lack of disease recognition have all played a role in the re-emergence of dengue fever. A tetravalent vaccine is under investigation, but experts estimate the vaccine is at least 5-10 years from being available. Increased public health efforts, including surveillance and control, are warranted.


Ms. O’Connell teaches at University of Medicine and Dentistry of New Jersey School of Health Related Professions in Piscataway, N.J. She is on the faculty of the physician assistant program, which is housed within the Robert Wood Johnson Medical School. She is also a contributing editor to The Clinical Advisor.