The surge of chikungunya cases in the Caribbean region is making ripples in Europe, and the disease could become a bigger threat there if it gains a firmer foothold in Central and South America, according to reports published yesterday in Eurosurveillance.

In other developments, Jamaica reported its first imported chikungunya case today, and a media outlet offered some new details on the first locally acquired cases in Florida, saying they involve a 41-year-old woman and a 50-year-old man. The cases were first revealed yesterday.

French and Spanish cases

The European Centre for Disease Control and Prevention (ECDC) in its latest weekly communicable disease threat report said several European countries have reported travel-linked cases, and separate reports in Eurosurveillance detailed cases in two of them, France and Spain

The French report describes 126 imported chikungunya cases detected in mainland France from May 2 through Jul 4, many in people who had traveled to the French Caribbean area. Between Nov 1, 2013, a month after the first cases in the Caribbean, and Jun 27, 475 cases were detected in France. In contrast, only 33 and 17 cases were reported in 2011 and 2012, respectively.

The authors noted that 47 of the patients with lab-confirmed infections live in districts in which Aedes albopictus mosquitoes, one of the main vectors of the disease, are established.

They warned that conditions are ripe for local transmission to occur, because most of France is immunologically naive to the virus, the vector is present, and the disease has been expanding its range over the past decade, with southern France having reported two local cases in 2010.

Air travel between France and the Caribbean islands of Martinique and Guadeloupe reached 2.5 million passengers last year. The report said many French travelers will be returning from outbreak areas at a time when the vector is active in France, which increases the threat of an outbreak on the French mainland.

The Spanish report described 10 imported cases that were detected in Spaniards who had traveled to Latin America from April through June. Seven had traveled to the Dominican Republic, two to Haiti, and one to both countries.

The patients' symptoms began when they were traveling or within 5 days of returning to Spain. Three patients reported work-related travel. Most patients said their symptoms improved after about 2 weeks, with three still on anti-inflammatory drugs 3 weeks after symptom onset.

Five cases are considered lab-confirmed on the basis of polymerase chain reaction testing, and five were positive on antibody testing and are considered probable cases.

The report notes that A albopictus is established in some parts of Europe, including Catalonia in Spain, where 9 of 10 recent Spanish case-patients live, the report said. Given that 5 of the patients were still viremic, the combination of the vector and virus poses a threat of local transmission, the authors warned.

In Caribbean, disease travels by sea

In a separate report, researchers from France and Italy explored the geographic spread of cases in the early phases of the Caribbean outbreak.

They found that the basic reproduction number (the number of new cases caused by a case introduced in a fully susceptible population) ranged from 2 to 4 in three French territories that were first affected—St. Martin, Martinique, and Guadeloupe—and was at a level consistent with a large and fast-growing outbreak.

They added that Guadeloupe had the highest estimate, and if the transmission rate continues unchanged, it will have the highest attack rate.

The researchers concluded that the risk of transmission in the Caribbean is inversely proportional to the distance between areas and is not driven chiefly by air transportation. So far, they found, places hit by the disease have had lower air travel volume than places not affected.

"Overall, our results suggest that short-range transportation such as boats and cruises hopping between islands are likely to have played a substantial role in the spread observed in the early phase of the chikungunya outbreak in the Caribbean," they wrote.

Risk factors in Europe

In a Eurosurveillance editorial, two experts from France and Spain list factors that increase the threat of chikungunya outbreaks in Europe.

One is that A albopictus is probably a competent transmitter of chikungunya in the Caribbean (though the question is not yet settled), they wrote. Local A albopictus mosquitoes fueled a 250-case outbreak in Italy in 2007, and mosquitoes are active in Europe now, they noted.

"The odds of controlling CHIKV [chikungunya virus] dissemination to Europe will become lower if, as expected, CHIKV spreads during the summer to continental South America," the editorial says. "Indeed, it is plausible that the long feared epidemic in South America will be ongoing for months and maybe years, continuously fuelling the flow of imported cases."

Other points the commentators make:

Lab capacity in Europe for detecting chikungunya is limited and needs to be increased.

Chikungunya poses a threat to blood safety in Europe, and blood donations by travelers returning from affected areas should be temporarily deferred.

Jamaica's first case

Meanwhile, Jamaica's first imported chikungunya case was confirmed yesterday, according to a Jamaica Observer story today, quoting Chief Medical Officer Kevin Harvey.

Harvey said the Caribbean Public Health Agency confirmed the case yesterday. The story did not name the affected country or territory that the patient had visited.

Harvey said the health ministry would step up its mosquito-control efforts and called on the public to protect themselves from the insects.

More on Florida cases

In other developments, a Miami Herald story yesterday offered some new information on the two locally acquired cases in Florida, the first such cases in the United States.

Citing Florida health officials, the story said the patients are a 41-year-old Miami–Dade County woman and a 50-year-old Palm Beach County man. The woman first fell ill on Jun 10, and the man got sick on Jul 1.

A county health official said the woman has since recovered, but the story didn't list the other patient's current condition.

Walter Tabachnick, director of the University of Florida's Florida Medical Entomology Laboratory in Vero Beach, told the newspaper that no one should be surprised by the cases.

"We expected this. Now the question is what are the cases to follow and can Mosquito Control itself do something to mitigate whatever those numbers might be?" he said.

Requena-Mendez A, Garcia C, Aldasoro E, at al. Cases of chikungunya virus infection in travellers returning to Spain from Haiti or Dominican Republic, April-June 2014. Eurosurveill 2014 Jul 17;19(28) [Full text]

Paty MC, Six C, Charlet F, et al. Large number of imported chikungunya cases in mainland France, 2014: a challenge for surveillance and response. Eurosurveill 2014 Jul 17;19(28) [Full text]

Cauchemez S, Ledrans M, Poletto C, et al. Local and regional spread of chikungunya fever in the Americas. Eurosurveill 2014 Jul 17;19(28) [Full text]

Noel H, Rizzo C. Spread of chikungunya from the Caribbean to mainland Central and South America: a greater risk of spillover in Europe? (Editorial) Eurosurveill 2014 Jul 17;19(28) [Full text]

See also:

Jul 18 Jamaica Observer story

Jul 17 Miami Herald story