UA Team Develops Model to Predict Spread of Debilitating Mosquito-Borne Virus, Wins International Competition

No vaccine or treatment exist for the chikungunya virus, also known as CHIKV, which causes debilitating joint and muscle pain. CHIKV continues to spread through the Western Hemisphere with 1.4 million suspected cases to date. A University of Arizona public health epidemiologist and mathematician joined forces to develop the most accurate infectious disease forecasting method, based on the CHIKV outbreak.

A  public health epidemiologist and a mathematician at the University of Arizona teamed up to win an international competition for their development of a model to predict an outbreak of chikungunya, a mosquito-borne viral disease that causes debilitating joint and muscle pain.

Chikungunya (pronunciation: chik-en-gun-ye), also known as CHIKV, is rapidly spreading worldwide and cases have been reported in 32 states, says the U.S. Centers for Disease Control and Prevention (CDC). Although rarely fatal, the severe pain is disabling and may be prolonged. No vaccine or treatment for the disease exist.

The UA team of Heidi Brown, PhD, MPH, assistant professor of epidemiology at  the UA Mel and Enid Zuckerman College of Public Health, and Joceline Lega, PhD, professor of mathematics, participated in the CHIKV Challenge, sponsored by the Defense Advanced Research Projects Agency (DARPA), which commissions research on behalf of the U.S. Department of Defense.

DARPA launched the CHIKV Challenge to accelerate the development of new infectious disease forecasting methods that would allow governments and health organizations to take more effective proactive steps to limit CHIKV’s spread. CHIKV’s debilitating symptoms pose a growing public health and national security risk, DARPA noted.

Scientists and researchers representing 38 institutions from around the world vied to develop the most accurate predictions of CHIKV cases for all Western Hemisphere countries and territories between September 2014 and March 2015.

Drs. Brown and Lega took first place and a $150,000 prize, which will support their ongoing collaboration.

Eleven winners were named, receiving a total of $500,000 in prize money, representing institutions that included the University of Southern California, Johns Hopkins University and the University of Massachusetts.

The competition also succeeded in creating new communities of expertise and connecting them with DARPA. “None of the winners had previous experience working with the agency, and participating teams were multidisciplinary, including not only specialists in public health and infectious disease, but also experts in mathematics, ecology, computer science and bioinformatics,” said Col. Matt Hepburn, DARPA program manager for the CHIKV Challenge. “This forward-thinking collaboration is exactly what it will take to stay ahead of the global threat that emerging diseases pose.”

Drs. Brown and Lega’s win exemplifies their collaborative work as well as the UA’s efforts to create proactive measures to minimize the spread of viruses and the UA’s interdisciplinary emphasis for solving grand challenges both locally and internationally.

CHIKV quickly is spreading through the Western Hemisphere and has been detected in Africa, Southern Europe, Southeast Asia and islands in the Indian and Pacific Oceans. In 2013, it was reported for the first time in the Caribbean; in 2014, local transmission was identified in Florida, Puerto Rico and the Virgin Islands, according to the CDC. As of May 2015, the Pan-American Health Organization reported nearly 1.4 million suspected cases and more than 33,000 confirmed cases of CHIKV.

Like the other teams, Drs. Brown and Lega were provided weekly reports from PAHO to develop their predictions, which then were tested against future reports from the organization. They were able to estimate the number, duration and peak of CHIKV cases that occurred in 2014 and 2015 in the Caribbean.

By design, CHIKV Challenge participants were allowed to update their predictions every month as they learned from experience—a challenge structure that sped development of better methods. On average, the top participants succeeded in doubling the accuracy of their predictions every two months, relative to their initial forecasts.

“From a mathematical modeling perspective, it was a unique opportunity to develop a model that was based on real data,” Dr. Lega said.

“Our model is extremely simple, which was at first quite surprising,” noted Dr. Lega, adding that she and Dr. Brown now are trying to determine if the approach could be used for other epidemics.

Dr. Brown said mosquito-borne diseases especially are difficult to predict due to the complexity of their systems.

“We try to model the interactions between mosquitoes, pathogens and humans—each adapting, evolving, changing their behavior by both the behavior of the other and the environment in which these interactions exist. Add to that a changing climate,” Dr. Brown said.

“Any headway we can make in predicting the number of cases, when cases will peak, when an outbreak will end or how severe an outbreak will be is helpful in reducing the disease burden.”

“You can look at number of cases: more than 1 million chikungunya cases in this one outbreak alone, or the 50 to 100 million dengue infections estimated by the World Health Organization to occur each year,” Dr. Brown said. “If you consider for each of these cases the physical burden, the economic burden on the individual, community or country, if you consider the efforts into vector control—these diseases are having a huge impact globally.”

Considering the burden of the West Nile virus, Dr. Brown cited research indicating that costs associated with U.S. hospital care and deaths as a result of the West Nile virus, as reported to the CDC, reached about $778 million during a period spanning 1999 to 2012.

“There are two reasons I study these diseases: One is the public health impact and the other is the intellectual challenge,” Dr. Brown said.