Dengue’s dynamics have changed dramatically since the end of World War II. As someone who has been focusing on dengue for the past 45 years, I would like to give you an overview of where dengue’s been, and how it got to where it is today.
Post-World War II to the 1960s
It was back in the post-World War II era that dengue began to extend its reach. Both the Allies and the Japanese armies spread both the viruses and the mosquito vectors and by the end of the war, the Asian region was what we call hyper-endemic; there was co-circulation of multiple viruses in most countries. And coinciding with this, it was post-World War II when several global trends began: unprecedented global population growth, economic boom, and growth of urban areas. All of which contributed to dengue’s growth.
Aiding dengue’s spread further is the advance of modern transportation, starting in the late 1960s, and accelerating in the 1970s and 1980s.The movement of people, animals, and commodities around the world is an ideal mechanism for moving the dengue virus. Besides these, there are also political factors explaining dengue’s advance. By the late 1960s, the US Surgeon General declared that the war on infectious diseases had been won, and the US and other governments redirected resources to other diseases, such as cancer. Suddenly, vector-borne diseases like dengue weren’t a public health priority anymore.
We became complacent and allowed the infrastructure we’d constructed to disintegrate.
Of growing populations, epidemics & research
If you look at the growth of Asian cities, it’s been truly dramatic – with cities having populations of millions. A shortage of housing, inadequate sewage infrastructure, and poor hygienic conditions make an ideal environment for the transmission of infectious diseases, such as dengue. And these factors have contributed to its growth. But it’s not just dengue’s presence that has changed; ideas about the disease have also changed over time. When the first epidemics occurred in the Philippines back in the 1950s, it was called Philippine hemorrhagic fever; outbreaks in Bangkok in 1958 were called Thai hemorrhagic fever, but the dengue virus caused all these.
Back in the 1970s, I was involved with a group calling for a revision of the WHO’s definition of dengue, which was very specific and, in my opinion, too narrow. But it wasn’t an easy process to redefine dengue.
Tropical Disease Research sponsored research into dengue in the early 2000s, and the findings confirmed what we had suggested previously: that dengue hemorrhagic fever was not a unique disease, it was part of the clinical spectrum associated with dengue infection. The WHO then created a new definition of the disease, breaking up dengue and severe dengue. There’s still a lot of controversy, some people don’t feel the new case definition is a good as the old one.
More recently, there’s been real change in how we deal with dengue over the past 10 years, thanks to research organizations and sources of funding, such as the Gates Foundation. We’ve now got a much better understanding of the transmission dynamics. And that can only help us combat the disease.