A New System Could Predict Deadly Dengue Outbreaks Four Months in Advance

Dengue fever is the nasty but less well-known cousin of malaria. Not in strictly a medical sense, and malaria ultimately kills more people. But even though both are spread by (different) mosquitoes, dengue has no vaccine and no specific drug treatment. Currently, the only way to avoid dengue is to avoid getting bitten, whereas you can take drugs to prevent contracting malaria. But what if we could develop a warning system that could predict in advance when we might be on the verge of a dengue fever outbreak? We could all be on the lookout.

A PhD candidate at Umeå University in Sweden believes she has developed a system to do just that: predict dengue outbreaks up to 16 weeks in advance.

Yien Ling Hii looked at medical data from Singapore and found that she could pretty accurately calculate the risk of an outbreak 3-4 months in advance, by examining the conditions that are favorable for the mosquitoes that transmit dengue—higher temperatures accompanied by higher rainfall. Based on these calculations, Yien developed a 1-10 scale to forecast risk at any given time.

Deploying such a system, Yien says, would allow medical personal and facilities to be prepared for an increase in cases, as well as allow local authorities to "implement preventative measures such as eliminating mosquito breeding habitats to control or even prevent the outbreak from happening."

Dengue fever is now endemic in over 110 countries. Though historically confined to the tropics and sub-tropics, as the globe's climate warms, locally-transmitted cases of dengue have been reported in areas where the disease had either once been eliminated or had not previously been seen before, both in Europe and North America.

In 2010 the first case of dengue fever in half a century was reported in Miami-Dade County, Florida. The same year 24 cases were diagnosed in Key West. Cases were also reported in the south of France and Croatia in the same year. In 2009, the NRDC released a report showing that the mosquito species that carry dengue—Aedes aegypti and Aedes albopictus both carry the disease—are now established in 28 US states. Other than the case in Miami, the only other areas of of the US that currently see cases of locally-transmitted dengue are along the US-Mexico border, and in Hawaii.

Since the 1960s the number of cases of dengue fever have increased globally, possibly because of ecological disruption, currently standing at 50-390 million people infected annually. Over 80 percent of people that get it are asymptomatic or show a fever. Five percent of people show the more dramatic and painful symptoms that give dengue its alternate name, breakbone fever. A smaller percentage develop the even nastier and more deadly dengue hemorrhagic fever. With medical intervention the mortality rate is less than 1 percent, but can reach 5% without treatment. Roughly 25,000 people die each year from the disease.

Though there is currently no vaccine, pharmaceutical companies are competing to develop one. Depending on who you listen to, a vaccine is either now two years away from public release, or about a decade off. Either way, there's plenty of reason to embrace Yien's forecasting system right now.