Mosquito Brings Mystery: What Officials Still Need to Learn About Zika

WASHINGTON – An epidemiologist whose area of expertise is the effect of mosquitoes on humans told a House committee that the ability to forecast the upcoming risk of Zika transmission is limited and the way to improve that status is additional funding for research.


Appearing before the House Science, Space and Technology Committee, Dr. Kacey Ernst, an associate professor in the Department of Epidemiology and College of Public Health at the University of Arizona, said assessing the Zika threat is made difficult by an “incomplete understanding” about how the virus is introduced into human cells and “our lack of ground-based surveillance of the geographic and seasonal distribution” of the Aedes aegypti mosquito that delivers it.

“Investment in developing and testing forecasting systems is needed,” Ernst told the panel. “Surveillance and forecasting activities, in particular, need long-term stable funding mechanisms to ensure scientific progress.”

Zika is only the most recent mosquito-borne disease to step to the international forefront, following in the footsteps of ailments like yellow fever, dengue fever and the West Nile virus. Most individuals contracting Zika are expected to suffer only a mild illness. But the Centers for Disease Control and Prevention has determined that a link exists between Zika during a woman’s pregnancy and severe birth defects.

Some adults, the CDC said, may experience serious neurological effects as a result.

The arrival of summer means a potential increase in the U.S. of the mosquito that carries the virus. The Gulf Coast of Texas and other regions are being cited as ground zero for the type of mosquito that carries Zika, which has now spread to more than 60 countries and territories in Latin America and the Caribbean.


The illness has also been found in U.S. territories. More than 500 people in the U.S. mainland have acquired the virus while traveling out of the country. More than 300 of those individuals are pregnant women. Ernst said Aedes aegypti is found in many urban areas throughout the southern U.S. and its potential range extends into the eastern seaboard.

The World Health Organization has declared Zika a “Public Health Emergency of International Concern.” Such declaration is reserved for a situation that is “serious, unusual or unexpected, carries implications for public health beyond the affected state’s national border and may require immediate international action.”

Ernst noted that Zika has only recently been perceived as a significant human threat. Much of what currently is assumed about the virus is based on the relationship between dengue and the Aedes aegypti, given they are closely related viruses that have been widely transmitted for hundreds of years.

Ernst acknowledged that the amount of information specific to Zika “is growing exponentially as the global health crisis has unfolded.”

The job now is to stop the spread. But Ernst told lawmakers that implementing procedures developed as a result of this research presents a “particular challenge.”

“The timely collection and dissemination of epidemiological and entomological information will be critical for both accelerating research and enabling effective operational programs to forecast and prevent pathogen transmission,” she said.


Investments into research, Ernst said, “would improve our capacity to respond, not only to the Zika virus pandemic, but to future threats of viruses that can be transmitted by mosquitoes.”

Researchers are not completely informed about the distribution of the Aedes aegypti mosquito in the U.S. because surveillance has not been consistent across jurisdictions. Many regions don’t have the resources necessary to carry out the mosquito surveillance needed to determine if the species has moved in.

“Aedes aegypti is a highly invasive species,” Ernst said. “It is originally from sub-Saharan Africa but has now spread throughout the warmer regions of the world, often hitchhiking in human-made containers like old tires. This mosquito exploits the ways we have changed our environment, including our use of many disposable containers, increasing movement of people and goods and migration of much of the population to dense urban centers.”

The Aedes aegypti “strongly prefers to feed on human blood and lives in and around our homes” and “extremely difficult to control.”

“The female mosquito lays her eggs above the water line on the side of the container then the eggs are submersed in water when it rains or the container is filled by people,” Ernst said. “They can exploit extremely small pools of water and can mature from egg to adult within seven to 10 days in only an inch of water.”


Dr. Daniel Neafsey, associate director of the Genomic Center for Infectious Disease Broad Institute at the Massachusetts Institute of Technology and Harvard University, also told the committee that funding for necessary research is critical to halt the spread.

“The Zika epidemic has caught the world off guard,” Neafsey said. “We lack fundamental understanding of how the virus moves from person to person via mosquitoes, information that is crucial for an effective response to the epidemic.”

Zika, Neafsey said, was “little studied prior to the recent epidemic that began in Brazil.” Despite the mosquito’s importance, researchers still “lack foundational resources to pursue DNA-based studies of the biology and transmission of Zika.”

“This resource is gap is critical,” he said.

Congress and the Obama administration currently are tussling over funding to address the Zika outbreak. The Senate passed legislation providing $1.1 billion for mosquito-extermination efforts, testing and vaccine research. The House is seeking a significantly smaller investment — $622 million, moving funds from other programs, including money dedicated to fight Ebola, to pay for it. The White House is seeking $1.9 billion.

And the feud doesn’t end with money. Rep. Lamar Smith (R-Texas), chairman of the House Science, Space & Technology Committee, chided the administration for failing to do enough to prevent the spread.


“Why has the administration not raised the travel alert level for countries with the highest number of Zika infections, such as Brazil and Colombia?” Smith asked rhetorically during the hearing. “Is the administration so worried about attendance at the Olympics in Brazil this summer that they’re willing to endanger American lives by not providing better warnings?”

Pregnant women, Smith said, “should be told to avoid nonessential travel to Brazil and Colombia. Anything less is putting political correctness ahead of the well-being of American women.”


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