With an Ever-Changing Climate, Our Tropical Disease Future is Nigh

A recent disease outbreak in Japan shows just how delicate the tropical-disease situation is, especially in a world afflicted by climate change.

In the past week, at least 55 people in Japan have contracted dengue fever, a disease that had all but vanished from the country since its last appearance at the close of World War II. Found in tropical and subtropical climates, it’s transmitted by a type of mosquito, Aedes aegypti. Because dengue fever isn’t transferred from human to human, the Japanese health ministry suspects that an infected individual must have arrived in Tokyo from abroad, entered Yoyogi Park (where all of the people affected appear to have visited), and given it to the local mosquitoes.

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A recent Japanese outbreak of dengue fever points to the swiftness of tropical disease, especially mosquito-borne ones.

Last year, an epidemic of dengue fever in Singapore resulted in 12,000 infections and four deaths. So far, Japan has been spared any fatalities, but the disease is crippling enough that it can develop into more a severe form, known as dengue hemorrhagic fever. Fortunately, officials predict that the strain will die out as cooler autumn air seeps into the affected regions.

This most recent Japanese outbreak points to the swiftness of tropical disease, especially mosquito-borne ones like dengue, malaria, chikungunya, West Nile virus, and more.

Here’s Euan McKirdy, writing for CNN.com:

The disease is on the rise, and over half of the world’s population live in dengue endemic areas. The Japanese outbreak comes as a WHO conference examining the links between health and climate change warned of the risks of infectious diseases like malaria and dengue which are strongly influenced by climate.

Higher humidity and temperatures mean mosquitoes can survive longer, increasing the likelihood for transmitting diseases and being able to travel to a wider geographic range.

“Vulnerable populations, the poor, the disadvantaged and children are among those suffering the greatest burden of climate-related impacts and consequent diseases, such as malaria, diarrhea and malnutrition, which already kill millions every year,” said Dr. Flavia Bustreo, WHO Assistant Director-General, Family, Women’s and Children’s Health in a press release.

While no vaccine for dengue fever exists, a French drug company called is creating an experimental dengue vaccine that has proved about 60 percent effective after a second trial.

Here’s Andrew Pollack, writing for The New York Times:

A question now is how widely such a vaccine would be adopted. Some experts hoped for a greater effectiveness, especially since in the first large trial, the vaccine was somewhat less effective in younger children, who are most vulnerable to the disease. Both trials were late-stage versions known as Phase 3.

“It’s certainly not anywhere close to what we had hoped, something that would reach up into the 90s,” said Dr. Scott B. Halstead, scientific adviser to the nonprofit Dengue Vaccine Initiative.

Still, with 50 to 100 million cases of dengue worldwide each year, the dengue vaccine would be a welcome preventative measure against some of the most severe cases.