Dengue and Chikungunya: Making the Diagnosis

Clinicians evaluating patients with acute febrile illness need to collect a travel history from the patient. Both chikungunya and dengue should be considered in the differential diagnosis if the patient traveled to any region of the tropics, particularly the Caribbean and Americas, where chikungunya has recently emerged.

Chikungunya and dengue are both acute febrile illnesses characterized by fever, myalgia, and lethargy. Some patients may also have maculopapular rash, nausea, vomiting, and headache.

Distinguishing features of chikungunya include potentially debilitating bilateral polyarthralgia and, in some cases, arthritis.
Although these signs and symptoms may assist in differentiating dengue and chikungunya, clinicians should include both illnesses in their differential diagnosis of patients with acute febrile illness and recent travel to the tropics. Such patients should also be evaluated for other serious conditions, such as malaria, leptospirosis, and other bacterial infections.

Diagnostic Tests for Suspected Chikungunya and Dengue

During the first five days of illness, RT-PCR to directly detect CHIKV or DENV nucleic acid should be performed on serum from suspected cases. Serum specimens collected five or more days after onset of symptoms should be evaluated for anti-CHIKV and anti-DENV IgM antibodies by immunoassay. If initial results are negative and dengue or chikungunya is still suspected, convalescent serum should be collected seven days or more after illness onset and retested to detect IgM antibodies.

Clinicians should also be aware that detection of anti-DENV IgG antibody has little utility in the diagnosis of acute dengue. Such results do not provide information about the timing of infection, as IgG antibodies that detect viral antigen may be the result of an infection that occurred in previous months or years and may fluctuate in their detectability over time. In addition, IgG antibodies against other flaviviruses (eg, West Nile, Japanese encephalitis, and yellow fever viruses) can cross-react with DENV, thereby yielding false-positive diagnostic results. Cross-reactivity may also occur with IgM antibodies, though less frequently.
Therefore, a thorough travel and vaccination history is necessary to accurately interpret dengue serologic diagnostic test results.

Management of Suspected Dengue and Chikungunya

Chikungunya is rarely fatal.
In contrast, early identification and proper clinical management for hospitalized dengue cases can reduce the case-fatality rate from 10% to less than 0.1%. Therefore, patients suspected of having dengue or chikungunya should be managed as having dengue until dengue can be ruled out.

Patients should be evaluated for the presence of warning signs of severe dengue (eg, persistent vomiting, severe abdominal pain). If present, patients should be hospitalized for close monitoring and management. If no warning signs are present, patients can be discharged home with anticipatory guidance that if such warning signs develop, they should return immediately for medical care. Vital signs and hemodynamic status should be monitored frequently in hospitalized patients.
Most patients who develop severe dengue do so in the 24-48 hours after defervescence, and this can occur rapidly and while the patient is lucid.
Hemodynamic status should be maintained with judicious use of isotonic intravenous fluids, which is the central component of dengue patient management.

Pain and fever in patients with suspected dengue or chikungunya should be managed with acetaminophen. If insufficient, narcotics such as morphine may be considered for pain management.
Aspirin and other NSAIDs should not be given to such patients because of the increased risk for bleeding manifestations if the patient has dengue.
If patients have been afebrile for at least 48 hours, have no warning signs of severe dengue, and still complain of joint pain, NSAIDs may be considered. Physical therapy may also be beneficial.

Clinical Considerations for Suspected Dengue and Chikungunya
Differentiating chikungunya from dengue can be challenging during the first week of symptoms.
Thus, both chikungunya and dengue should be considered in patients returning from the tropics with acute febrile illness, AND in the tropical countries.
Diagnostic testing by RT-PCR and/or IgM immunoassay should be requested for such cases and the results reported to public health authorities. Clinicians should be aware that detection of anti-DENV IgG antibody alone is not necessarily indicative of recent DENV infection.
The dengue and chikungunya viruses are both transmitted by Aedes species mosquitoes. Because vaccines to prevent dengue and chikungunya are not available, the best way to reduce the risk for infection is to avoid mosquito bites by using air conditioning or screens when indoors, and by using insect repellents and wearing long sleeves and pants when outdoors. It is also important to protect people with suspected dengue and chikungunya from mosquitoes during the first week of illness to prevent further spread of the virus.

G Mohan.