The leader of infectious disease research in the U.S. government says that the pandemic of Zika virus spreading across the global south, which may be causing an epidemic of birth defects in South America, heralds a new kind of infectious disease threat. It is exploding at the same time and in the same areas as other diseases carried by the same vector, mosquitoes—and thus demonstrates that it is no longer enough to be prepared to counter one disease at a time.
Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, writes in a study released Wednesday in the New England Journal of Medicine with Dr. David Morens of NIAID that Zika arrives in the Americas on the heels of three other mosquito-borne diseases: West Nile virus, in the United States since 1999 and still causing cases; chikungunya, which has invaded the Caribbean and Central America; and dengue, which moved north from the tropics to become re-established in Florida.
“Zika virus forces us to confront a potential new disease-emergence phenomenon: pandemic expansion of multiple, heretofore relatively unimportant arboviruses previously restricted to remote ecologic niches,” they write. “To respond, we urgently need research on these viruses and the ecologic, entomologic, and host determinants of viral maintenance and emergence. Also needed are better public health strategies to control arboviral spread.”
As I reported a month ago, Zika—which is often a mild disease of fever, aches and rash—has spiked extraordinary alarm in Brazil because it is overlaid with, and may be causing, an epidemic of babies being born with unusually small brains and heads. The microcephaly, as it is called, has not been proven to be caused by Zika, but people are so alarmed that, as one commenter here wrote, “People here are very worried about Zika virus, especially pregnant women and the ones trying to get pregnant… In the timespan of two weeks my city has gone from ‘never heard of this virus’ to thousands of infecteds, inclunding myself, my husband, and several relatives and friends of mine.”
At that point, Zika had spread from the shoulder of South America up through Central America and into Mexico. Since then, it has also been found in Puerto Rico, in a person who had not traveled outside the country—putting it on U.S. soil though not in the continental United States—and on Monday, in the vicinity of Houston, though that person was probably infected while traveling.
Zika, dengue and chikungunya are spread by the same mosquito species, A. aegypti, which has adapted to live near humans: It flourishes in small pools and containers of water, like a flower pot or the puddle in a tire. There are limited tests for the diseases—none for Zika, and sparsely distributed ones for the other two —and no treatments for them other than supportive care. Their initial symptoms are similar, but because they have different serious complications—birth defects for Zika, hemorrhagic fever for dengue, reactive arthritis for chikungunya—it is possible to make mistakes in the early stages that can make the late consequences worse.
The researchers argue that all of this adds up to a new responsibility to both prevent diseases, and also confront that prevention is a broader task than has previously been understood. In the case of these mosquito-borne diseases, a “one bug one drug” approach is inadequate, they say. What is needed: broad-spectrum drugs that can address whole classes of viruses, and vaccine “platforms” that can be adjusted as needed to prevent infection with whatever virus arrives on the scene. But more broadly, these diseases provide a lesson, of how rapidly and lethally emerging threats—possibly, multiple threats— will take us by surprise if we do not prepare.
“In our human-dominated world, urban crowding, constant international travel, and other human behaviors combined with human-caused microperturbations in ecologic balance can cause innumerable slumbering infectious agents to emerge unexpectedly,” they write. “We clearly need to up our game with broad and integrated research that expands understanding of the complex ecosystems in which agents of future pandemics are aggressively evolving.”
Previously on Phenomena:
Dec. 2, 2015: Mosquitoes Bring Disease, Maybe Birth Defects, to US Border.