In 1961, during the first dengue outbreak physician Scott Halstead ever witnessed, children poured into Bangkok’s hospitals, passing and vomiting blood, faint from blisteringly high fevers. Twenty percent of the children would die within a few days as doctors scrambled to find treatments, with some in nearby Vietnam even plunging children into ice baths in an attempt to hold down their soaring temperatures.
The deadly illness caused by dengue virus wasn’t yet known as dengue in Thailand; doctors there referred to it as “Chinese medicine poisoning” based on a demographic quirk. Although half the city’s population was Chinese, the only time Thai doctors—who practiced Western medicine—treated Chinese children was when the children had been stricken with this mysterious, deadly illness. Thus, doctors imagined that a horrific poisoning caused by Eastern remedies was responsible for the influx of Chinese patients.
Instead, Halstead explains, Chinese parents had quickly learned that the hospital, rather than traditional medicine, was the best bet—however slim the chances—for defeating dengue.
Halstead who was drafted into the US Army after World War II and originally sent to Japan in 1957 to study encephalitis, had just settled into a lab across the street from the Children’s Hospital in Bangkok. “Everything I’ve ever done,” he says in retrospect, “is related to the treatment of dengue.”
In the years that followed, he and his colleagues identified dengue as the cause of the outbreak and began tracking the four different versions of the virus, each transmitted by mosquitoes. Among their seminal discoveries, the researchers learned that the hemorrhagic disease that they saw in 1961 was most common when a child is infected with a second type of dengue—a finding that would prove pivotal in the decades-long search for a vaccine that continues today.
The World Health Organization estimates that more than 2.5–3 billion people, or more than 40 percent of the world’s population, are now at risk of being infected with dengue—including some in the developed world.
But as research efforts have evolved, so has the reach of dengue infections. The disease has now become prevalent in more than 100 countries, causing as many as 100 million infections per year. And it’s still spreading. In the past few years, cases of dengue have popped up in Texas, Florida, France, and Croatia.
Of the 500,000 cases of severe dengue requiring hospitalization and the roughly 24,000 deaths they cause each year, most are in children, according to the WHO. And control measures have been met with challenges. One high-profile vaccine trial conducted by the French vaccine company Sanofi Pasteur partially failed last year, leaving investigators scratching their heads.
The defeat comes amid fears of some researchers that vaccines have the potential to exacerbate a dengue infection rather than protect against it. “We’re in a mess,” Halstead says bluntly.