Dengue got its start with the growth of global trade in the 17th century. It’s an illness of inter-connectivity.
The virus itself comes from monkeys in the jungles of southeast Asia. But the mosquito that spreads it to humans evolved in Africa.
After the two combined, the illness spread across the world on sailing ships, including to the American colonies.
In fact, Dr. Benjamin Rush, who signed the Declaration of Independence, is also famous for describing dengue during an outbreak in Philadelphia.
But dengue didn’t become a huge global health problem until World War II.
Scott Weaver is an infectious disease expert at the University of Texas Medical Branch at Galveston.
“Following World War II, there were a lot of people moving into cities in Asia. Aedes aegypti, the mosquito vector, became much more abundant in those cities, and air travel increased so that people who are infected can transmit the virus around the globe now.”
Now dengue circulates in tropical countries from Southeast Asia to the Caribbean and Latin America, infecting at least 100 million people a year.
So how dangerous is it to us Houstonians, now that dengue has been found here?
Weaver says for the moment, West Nile virus is more of a threat to Houstonians, because it’s more likely to cause brain inflammation, especially in old people, and that can lead to death.
But dengue shouldn’t be underestimated either.
“You’re pretty sick.”
Dr. Robert Tesh is an epidemiologist at UTMB.
He accidentally contracted dengue while researching it in a lab in Hawaii.
Tesh says that in addition to the characteristic high fever and joint pain of dengue, he got very, very sad.
“I was very depressed, and that’s one of the symptoms of the disease. Benjamin Rush described young women crying when they had dengue. You just don’t feel like talking, you feel awful, you just want to sit and be quiet. And I couldn’t eat anything; I was vomiting all the time.”
Tesh recovered from dengue, like most victims do.
And some people never even get symptoms or know they’re infected.
However, a small minority of people can get a form of the disease called dengue hemorrhagic fever, a complication that — like West Nile — can involve encephalitis and even death.
However, this hemorrhagic form of dengue usually develops only after you’ve been exposed to two different subtypes of dengue.
And there’s only one subtype of the virus here in Houston, so far.
Again, Dr. Weaver:
“As long as we don’t have a lot of circulation of dengue and multiple serotypes of dengue coming into places like Houston, I don’t think we’re going to have a high risk for severe disease. We’re going to have a risk for occasionally having dengue fever, which is highly debilitating, very unpleasant to have, but not usually life threatening. Whereas West Nile is always life-threatening to the older age groups.”
Nevertheless, there’s a different subtype of dengue in the Florida Keys.
So that virus wouldn’t have far to travel to Houston to start mixing with the type we have here, and cause the more serious form of the illness.
In the meantime, scientists are working on a vaccine.
It’s complicated by the fact that there are four different dengue subtypes circulating in the world. A vaccine would have to be effective against all four subtypes.
And now scientists have just confirmed the emergence of a fifth subtype from a forest in Malaysia.