Derailing disease

UF researcher uses analytical modeling to understand and slow the spread of disease

By Laura Mize

Ira Longini, Ph.D.

Agent X is coming. No one knows when or where it will appear, or what it will do when it does. But that doesn’t mean we can’t be prepared.

Ira Longini, Ph.D., a professor of biostatistics in UF’s colleges of Medicine and Public Health and Health Professions, a member of the Emerging Pathogens Institute and co-director of the Center for Statistics and Quantitative Infectious Diseases, is working to ensure humanity is as ready for the debut of Agent X as we can be.

You see, Agent X is a nickname for the next new disease that will inevitably appear some day and begin to spread around the globe before we know much about it.

Nine years ago, Agent X turned out to be severe acute respiratory syndrome, or SARS. SARS emerged in Asia in February 2003 and killed 812 people by the time the World Health Organization declared it contained in early July. About 8,400 people contracted the disease, which scientists believe spread to humans from animals in China.

It spread in Asia and to Europe, Australia and North America, but quick actions by public health officials worldwide led to its containment in less than a year. The keys, Longini said, were gathering certain facts about the outbreak: when and where people had come down with the disease, and who had been exposed to it but not become ill. These factors, he said, allow investigators to understand how fast a disease spreads and possible ways to control it.

“That’s exactly what was done with SARS,” Longini said. “We had no treatment. We had no vaccines against SARS. But once we understood that it was spreading at a pretty slow rate and it had about a two-week or 10-day ‘serial interval,’ or time between one infection and another, and that every infected person was symptomatic, we controlled SARS with surveillance and containment.”

This strategy, called analytic modeling, also is helpful in studying familiar diseases. Longini and other UF researchers are members of Models for Infectious Disease Agent Study, a network funded by the National Institute of General Medical Sciences. They’re taking strategies similar to those that helped contain SARS and applying them to pathogens such as smallpox and anthrax. These diseases don’t plague the world today but could be used as weapons.

Longini and his collaborators also study diseases such as cholera, influenza, typhoid and dengue fever, which are prevalent in much of the world. Last year, the journal the Journal of the Royal Society Interface published an article authored by Longini and several other researchers explaining how Tamiflu-resistant influenza strains appeared, then became the dominant strains in just three years.

“Between September and April we have influenza epidemics in the northern hemisphere, and then between June and September, we have them in the southern hemisphere,” Longini said. “Throughout the tropics, we have sporadic influenza all year round. Basically, these resistant strains, by getting shuffled around the planet in kind of a random way, led to this quick buildup in resistance.”

The work will help researchers predict how fast other resistant strains will become dominant and how the spread of such resistance might be slowed.

“It’s just part of a larger effort to understand and control influenza and other emerging infectious diseases,” Longini said.