Nasty epidemic, neat science
by Eric Sorensen | © Washington State University
Dennis Garcia had good reason to be nervous.
Flu season was just a few months away, and in the summer of 2009, outbreaks of the H1N1 virus known as “swine flu” were popping up around the world. It was a novel virus, so rare that humans had yet to start developing immunity to it. A similar scenario was in place for the Spanish flu of 1918, an H1N1 outbreak more deadly than the Black Death bubonic plague.
By late August, as the first wave of students returned to Washington State University’s Pullman campus, the World Health Organization had seen the virus in scores of countries, with nearly 3,000 deaths worldwide.
“We were really worried about it because we knew it was coming, we knew we weren’t going to have a vaccine, with the previous novel infection killed thousands of people during World War I,” says Garcia, who was serving as assistant director of the WSU Health and Wellness Services medical clinic at the time. “Being the optimist that I am, I said, ‘Well, we’re dealing with 18- to 24-year-olds, they’re healthy, and modern medicine is leaps and bounds ahead of what it was in 1918. Hopefully we’ll be OK.’”
The fall semester hadn’t even started when the first cases came in—11 one day, and just two days later, 47. Not two weeks later, the clinic’s doctors and nurses saw 164 H1N1 patients, attending to a total of nearly 1,000 sick people, plus hundreds more by phone. They ran out of Tamiflu, an antiviral medication. Garcia set aside an area in the clinic just for the flu cases. At one point, school officials considered cancelling the first home football game, against Stanford.
But as game day approached, Garcia noticed the flu wasn’t as intense as he feared. One young man was hospitalized with bilateral pneumonia, but for the most part people felt awful for three or four days and were close to normal within a week. No one died. The Stanford game went on, with the spectators warned of the Pullman outbreak ahead of time.
Still, WSU took on an unwanted national distinction as having had one of the largest H1N1 outbreaks at an American college. In retrospect, Garcia sees some circumstances that made College Hill an ideal environment for passing germs.
“All of the freshmen females that want to be in a sorority are here on campus and they’re all in groups of 40—close, tight—going from one sorority house to another,” Garcia recalls. It’s a hugely social occasion. The women are shaking hands, hugging, “and they’re provided refreshments as they walk into the door that are hand-poured and hand-delivered. The opportunity for spread was optimal. And it spread.”
The Pullman epidemic also served up something of an ideal phenomenon for scientific study. At the time, Elissa Schwartz, an assistant professor of both math and biological sciences, was teaching students about the behavior of epidemics in a closed population. Right here in Pullman, she realized, was a living example. “The students didn’t like it at all at first because they were so sick of hearing about swine flu,” she says.
She had her students search the scientific literature looking for studies that tracked actual epidemics in closed populations, which have no movement in or out. They found very few. They had a fairly closed population in Pullman, more specifically, College Hill, where many students live, often in shared housing. When they do leave the house, they’re on campus, in close proximity to more people. With the exception of semester breaks and the occasional road trip, they rarely leave.
“We thought, ‘Oh, if we can get data on this, then that will be real live data, not simulated data, on the actual number of infections in this community,’” Schwartz says. “And it turned out that the Health and Wellness Services was tracking it, which was great.”
To analyze the numbers, Schwartz used a computer model called FluTE, which can simulate the transmission of an influenza virus across a population and tease out things like how many become infected, how many symptoms-free carriers first had it, and what strategies would make the biggest difference in containing its spread.
Transmissibility is measured by the R0, or R naught, the average number of people infected by one person in a fully susceptible population. Schwartz pegged the R naught for the Pullman outbreak at 2.2, meaning one sick person ended up passing his or her infection on to roughly two others. That’s close to the rate attributed to the 1918 pandemic.
Schwartz’s analysis also suggests the outbreak was started by as few as 20 people initially infected by the virus. It’s a remarkably low number of people given the number of people who ultimately got sick.
“But given that it was spreading as fast as it was,” Schwartz says, “and people were living in close proximity as they were, which means the contact rate is really high, then perhaps it wasn’t low.”
Finally, Schwartz wondered what strategy might have worked best to contain the outbreak, from vaccinations to isolation and quarantines, or all of the above. Sick people were asked to isolate themselves from others, but that is difficult, Schwartz says. A sick person can still share a bathroom with others. But a quarantine, which would contain both sick and potentially exposed people, might be hard to enforce if people felt the symptoms were mild enough.
“I think what this does say is vaccination, to say the obvious, is probably the best way to control these types of infection,” says Schwartz, whose study was published last year in the Journal of Biological Systems.
Garcia agrees, for more anecdotal reasons.
For some four decades of flu seasons, he figures, he was vaccinated regularly. While flu strains tend to vary from year to year, antibodies created in response to one vaccine can often provide what’s called a cross-protection to other, similar strains, including novel viruses. As it happened, some 40 Health and Wellness workers were in the trenches helping sick students. Only two—young people with fewer vaccines under their belt—got sick, says Garcia.
“I often tell my students now, ‘This is why you should get the flu shot,’” he says. “‘It will protect you when you’re 40 in the event that something like this ever happens again. And it will, because this influenza virus mutates every year.’”
Comments are temporarily unavailable while we perform some maintenance to reduce spam messages. If you have comments about this article, please send them to us by email: email@example.com