Travelers to Thailand at Risk of Chikungunya Virus Infection

By Marilynn Larkin

April 02, 2019

NEW YORK (Reuters Health) - Confirmed cases of chikungunya virus in travelers returning from Thailand's tourist areas mean that visitors to the country are at increased risk, and the virus may spread to other nations, researchers warn.

"Chikungunya virus is currently circulating in the most touristic areas of Thailand and there is evidence of local transmission in Malaysia and potentially other neighboring countries," Dr. Emilie Javelle of French Armed Forces Health Service, Laveran Hospital and IHU Méditerranée Infection, GeoSentinel/EuroTravNet in Marseille told Reuters Health.

"All travelers to southern Thailand, including those from the US, are at risk of developing chikungunya disease since the virus is symptomatic in around 90% of infected cases," she said by email.

"It is not a highly fatal illness, but one characteristic is the articular tropism resulting in disabling arthralgia and/or arthritis," she noted. "All joints may be involved, and several at the same time. Joint pains, swelling or stiffness may persist for many months or even longer (up to 50% at two years) and few patients consider they have totally recovered from chikungunya, especially if they had pre-existing rheumatic disorders."

Therefore, prevention is "crucial," she said, "especially for older travelers." Chikungunya viremia "may reach high loads which enhance transmission and may lead to massive outbreaks as occurred in Indian Ocean (2005-2006) and Central and South America (2013-2014)."

In their Eurosurveillance report, online March 7, Dr. Javelle and colleagues provide data on nine travelers with confirmed chikungunya virus infection who returned from Thailand to Sweden, Switzerland, the UK, Romania, Israel and France, and were diagnosed in January and February 2019.

The median age was 37, and seven of the nine were female. Three patients had underlying conditions, including hypothyroidism, hypertension and pancreas resection; familial hypercholesterolemia; beta thalassemia and carpal tunnel syndrome.

The average length of stay in Thailand was 22 days and the average delay between arrival and onset of chikungunya symptoms was 16 days.

All patients had fever and joint pain; seven had a rash; five had a headache; two had lymphadenitis; and five developed edema or joint swelling. One patient had malaise, fever, and loss of consciousness leading to head trauma.

Three patients were hospitalized in Thailand and one after returning home

Eight received non-steroidal anti-inflammatory drugs for persistent arthralgia; one was treated with intravenous corticosteroids during the acute stage in Thailand.

Only two recovered completely within three weeks, whereas one patient, a woman in her 70s, developed post-chikungunya chronic rheumatism lasting more than three months and remains heavily impaired.

"These sentinel tourists support the intensification of chikungunya virus circulation in Thailand and highlight the potential for importation to areas at risk of local transmission," the authors conclude.

Dr. Daniel Caplivski, Director of the Travel Medicine Program and Professor of Infectious Diseases at the Icahn School of Medicine at Mount Sinai in New York City, commented by email, "Based on the data from the outbreak in the Americas in 2013, this virus has not been seen causing many locally transmitted cases in the US."

"Both mosquito vectors, Aedes aegypti and Aedes albopictus, are found in the US," he told Reuters Health by email. "States such as Florida and Texas, where Aedes aegypti is more common, are at a slightly higher potential risk to see locally transmitted cases; however, because of living conditions that include less mosquito exposure than in other countries due to houses with sealed windows and air conditioning, the likelihood of sustained local transmission remains low in the mainland US."

"Chikungunya infection also appears to provide protective immunity against future infection," he noted, "so reintroduction of the virus by a traveler from Thailand into Puerto Rico or the US Virgin Islands also seems unlikely to cause the large-scale outbreak that was seen in 2013, when the vast majority of local population did not have immunity yet."

"This article is a helpful reminder to clinicians who may be seeing returning travelers from Southeast Asia with joint pains and fevers," he said. "It is important to distinguish this particular infection from similar infections such as dengue, zika and even malaria. Molecular and serologic tests are the most direct way to confirm a diagnosis. A peripheral blood smear to look for parasites is the most commonly ordered test to exclude malaria."

"As the summer travel season approaches, it is important to review insect prevention measures with travelers heading to the tropics," he advised. "The basic interventions with skin repellents and clothing and gear treatment with insecticide can go a long way towards prevention."

"For clinicians evaluating travelers returning from Thailand or other countries in the tropics, a heightened awareness of local epidemiology can help guide appropriate testing," Dr. Caplivski concluded.

SOURCE: http://bit.ly/2WwY4AK

Euro Surveill 2019.

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