GENEVA - The French overseas territory of La Reunion is experiencing an unprecedented outbreak of dengue fever which could be spread by tourists to other countries, the World Health Organization said on Wednesday.
Dengue is a mosquito-borne virus that may be thriving because of a lack of immunity among the population of the Indian Ocean island, the WHO said, adding the virus may also have spread unnoticed in recent years as asymptomatic cases may have contributed to the transmission cycle.
This year there have been 1,816 dengue cases confirmed, as of April 23. All of them were "autochthonous" - local rather than imported by tourists and travelers. In the week to April 23, there were 428 probable and confirmed cases reported, compared to fewer than 100 in all of 2017.
"Although sporadic autochthonous dengue fever cases and clusters have been reported in Reunion before, the upsurge of cases since the beginning of 2018 is unprecedented," the WHO said.
"Reunion is a popular tourist destination and the likelihood of dengue virus introduction to other countries is heightened by the current outbreak."
There have been 50 hospitalizations on La Reunion this year compared to 12 in all of 2017, the WHO said.
Dengue is the world's fastest-growing infectious disease, afflicting hundreds of millions of people worldwide. It causes half a million life-threatening infections and kills about 20,000 people, mostly children, annually.
The world's only licensed vaccine against dengue, Sanofi's Dengvaxia, is at the center of a health scare in the Philippines where the government suspended its use last year amid safety fears.
The French drugmaker warned in November that Dengvaxia could increase the risk of severe dengue in some cases in people who had not been previously exposed to the disease.
In 2016, the Haut Conseil de la Sante Publique (HCSP), a public body close to France's health ministry, advised against the use of Dengvaxia in the country's overseas territories, Reuters reported in December.
A health ministry spokeswoman no change to the HCSP position was likely before the European Medicines Agency ends its current review of the vaccine.
The WHO said last month Dengvaxia should now be used only after testing on individuals to assess whether they have previously been exposed to the infection.