Conference Coverage

Zika’s not the only mosquito-borne virus to worry about


 

EXPERT ANALYSIS AT PDA 2016

NEWPORT BEACH, CALIF. – As the spread of Zika virus continues to garner attention in the national spotlight, two other mosquito-borne viral infections pose a potential threat to the United States: dengue fever and chikungunya.

At the annual meeting of the Pacific Dermatologic Association, Iris Z. Ahronowitz, MD, shared tips on how to spot and diagnose patients with these viral infections.

Dr. Iris Z. Ahronowitz

Dr. Iris Z. Ahronowitz

“You really need to use all the data at your disposal, including a thorough symptom history, a thorough exposure history, and of course, our most important tool in all of this: our eyes,” said Dr. Ahronowitz, a dermatologist at the University of Southern California, Los Angeles. Reaching a diagnosis involves asking about epidemiologic exposure, symptoms, morphology, and performing confirmatory testing by PCR and/or ELISA. “Unfortunately we are not getting these results very quickly,” she said. “Sometimes the turn-around time can be 3 weeks or longer.”

She discussed the case of a 32-year-old woman who had returned from travel to Central Mexico (J Am Acad Dermatol. 2008;58[2]:308-16). Two days later, she developed fever, fatigue, and retro-orbital headache, as well as flushing macular erythema over the chest. Three days later, she developed a generalized morbilliform eruption. Her white blood cell count was 1.5, platelets were 37, aspartate aminotransferase was 124 and alanine aminotransferase was 87.

The differential diagnosis for morbilliform eruption plus fever in a returning traveler is extensive, Dr. Ahronowitz said, including measles, chikungunya, West Nile virus, O’nyong-nyong fever, Mayaro virus, Sindbis virus, Ross river disease, Ebola/Marburg, dengue, and Zika. Bacterial/rickettsial possibilities include typhoid fever, typhus, and leptospirosis.

Under a magnification of 165X, this hematoxylin-eosin-stained photomicrograph depicts the cytoarchitectural changes found in a liver tissue specimen extracted from a Dengue hemorrhagic fever patient in Thailand. © World Health Organization

This photomicrograph depicts changes found in a liver tissue specimen extracted from a dengue hemorrhagic fever patient in Thailand.

The patient was ultimately diagnosed with dengue virus, a mosquito-borne flavivirus. Five serotypes have been identified, the most recent in 2013. According to Dr. Ahronowitz, dengue ranks as the most common febrile illness in travelers returning from the Caribbean, South American, and Southeast Asia. “There are up to 100 million cases every year, 40% of the world population is at risk, and an estimated 80% of people are asymptomatic carriers, which is facilitating the spread of this disease,” she said. The most common vector is Aedes aegypti, a daytime biting mosquito that is endemic to the tropics and subtropics. But a new vector is emerging, A. albopictus, which is common in temperate areas. “Both types of mosquitoes are in the United States, and they’re spreading rapidly,” she said. “This is probably due to a combination of climate change and international travel.”

Dengue classically presents with sudden onset of fevers, headaches, and particularly retro-orbital pain, severe myalgia; 50%-82% of cases develop a distinctive rash. “While most viruses have nonspecific lab abnormalities, one that can be very helpful to you with suspected dengue is thrombocytopenia,” she said. “The incubation period ranges from 3 to 14 days.”

Rashes associated with dengue are classically biphasic and sequential. The initial rash occurs within 24-48 hours of symptom onset and is often mistaken for sunburn, with a flushing erythema of the face, neck, and chest. Three to five days later, a subsequent rash develops that starts out as a generalized morbilliform eruption but becomes confluent with petechiae and islands of sparing. “It’s been described as white islands in a sea of red,” Dr. Ahronowitz said.

A more severe form of the disease, dengue hemorrhagic fever, is characterized by extensive purpura and bleeding from mucosa, GI tract, and injection sites. “The patients who get this have prior immunity to a different serotype,” she said. “This is thought to be due to a phenomenon called antibody-dependent enhancement whereby the presence of preexisting antibodies facilitates entry of the virus and produces a more robust inflammatory response. Most of these patients, even the ones with severe dengue, recover fully. The most common long-term sequela we’re seeing is chronic fatigue.”

The diagnosis is made with viral PCR from serum less than 7 days from onset of symptoms, or IgM ELISA more than 4 days from onset of symptoms. The treatment is supportive care with fluid resuscitation and analgesia; there’s no specific treatment. “Do not give NSAIDs, which can potentiate hemorrhage; give acetaminophen for pain and fevers,” she advised. “A tetravalent vaccine is now available for dengue. Prevention is so important because there is no treatment.”

Next, Dr. Ahronowitz discussed the case of a 38-year-old man who returned from travel to Bangladesh (Int J Dermatol. 2008;47[1]:1148-52). Two days after returning he developed fever to 104 degrees, headaches, and cervical lymphadenopathy. Three days after returning, he developed severe pain in the wrist, knees, and ankles, and a rash. “This rash was not specific, it was a morbilliform eruption primarily on the chest,” she said.

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