At Sandia Lab research is being conducted on predicting the effects of an epidemic on a given population, using algorithms and computers that seem to correlate well with past outbreaks.
[Jaideep] Ray says that characterizing diseases requires observations of real outbreaks and then building computer models around them. He did this for a 1979 anthrax outbreak in Sverdlovsk (called Yekaterinburg, after the fall of the Soviet Union), a city of about 1.2 million people in central Russia. Initially the Soviets said the victims contracted the disease by eating anthrax-contaminated meat or having contact with dead animals. At the end of the Cold War American physicians reviewed documents published by pathologists who performed autopsies during the epidemic, confirming the pathogen was airborne. Records showed that 80 humans were infected, most of them by inhaling the pathogen. A total of 68 died of the disease.
Using the computer program, Ray ran the data obtained from hospital records of people who became sick in the early days of the epidemic. The program automatically tried many combinations of the unknown number of infected people, time and dose of anthrax exposure until it got as close to the real observation as possible. In the final runs, using data from the first nine days of the 42-day outbreak, the model inferred that almost certainly less than 100 people had been infected, with the most probable number around 55.
That was “pretty close,” to the real event, he says. The program, which also estimated the time of the release and the dose of anthrax inhaled, took 10 minutes to run.
“If they had had this program in 1979 the Soviet officials would have known that this was going to be a small outbreak,” Ray says. “Instead they got into a panic and vaccinated 50,000 to 60,000 people — the whole southern end of the city.”
Nigerian smallpox epidemic
After proving the software actually works, he turned his attention to communicable diseases, specifically smallpox. He modeled a documented smallpox outbreak in Nigeria in 1967, which broke out in a fundamentalist sect (Faith Tabernacle Church, FTC) in the town of Abakaliki. The sect consisted of 120 people who lived in nine different compounds, along with 177 of their nonsectarian brethren. The FTC members mixed strongly in their compounds and across compounds at church four times a week and social visits.
A small girl first introduced the disease into the population. It spread rapidly in her compound and jumped to other compounds via the church and social visits. The sect members refused medical treatment and did not quarantine the sick and contagious members. While the World Health Organization (WHO) monitored the outbreak and kept records of who got sick and when, it did not record the dates of recovery or deaths of the infected people.
Of the 32 people who became infected during the epidemic, 30 were FTC members.
Full story: Sandia researcher develops inference technique that estimates how many people will fall sick in an epidemic