Foreign Policy recently reported that an ISIS laptop computer captured in Syria includes instructions on how to weaponize bubonic plague. Yes, the plague. The plague that caused the Black Death pandemic that killed roughly 25 million Europeans in the 14th century.
But is a plague weapon even possible? How crazy is it to think that plague could be found and turned into a usable weapon? Here's a rundown:
The plague is still hanging around
You don't have to go to a medieval graveyard to find the bacteria that causes plague: Yersinia pestis.
The bacteria is still around because plague never really went away, although its burden on humanity has lessened significantly over time. Today, most plague cases are in rural areas, where people get the disease from infected fleas associated with wild rodents such as squirrels.
In recent years, human cases of plague have appeared across the world, even here in the United States. The bubonic type of the disease, named after its characteristic painful lymph nodes, is the most common kind seen today.
But bubonic plague is also very treatable
Here's the good news: people who come down with bubonic plague generally get diagnosed, get treated, and get better. Only about 11 percent of US cases from 1990–2010 have been fatal.
So why isn't plague killing like it used to? Unlike in the Middle Ages, we now have antibiotics that treat it — and those antibiotics tend to be pretty effective. On the downside, however, there's no commercially available vaccine in the US to prevent plague infection.
However, there's one type of plague infection that's very deadly: pneumonic plague
Now, there's one big exception here. If plague bacteria gets into your lungs, it can cause what's called pneumonic plague. And pneumonic plague is highly lethal. The World Health Organization calls it "one of the most deadly infectious diseases."
Pneumonic plague is fatal in almost all cases if not treated with antibiotics. And it can kill within 24 hours, which means that people with symptoms absolutely need to get treated immediately. And people with pneumonic plague can also transmit the disease to others by coughing up the bacteria from their lungs into the air, where someone else might breathe it in.
"They expel respiratory droplets, and it can go person to person to person to person, which is one of the things that has made the use of plague for bioterror very scary," says Ken Gage, who oversees flea-borne diseases at the CDC.
Pneumonic plague is what gets bioterrorism experts worried. One frequently cited 1970s World Health Organization worst-case-scenario estimate predicts a death rate of about a quarter of cases. The US Centers for Disease Control and Prevention classifies pneumonic plague as a Class A bioterrorism agent, its riskiest category, which also includes smallpox, anthrax, and viral hemorrhagic fevers such as Ebola. The risk evaluation is based on factors such as how easily it can be transmitted and its death rate.
It's not easy to make a pneumonic plague weapon
To make a pneumonic plague weapon, you'd have to aerosolize the bacteria and get it into people's lungs. This is much harder than simply throwing it into a spray bottle. Bacteria are living things with needs, and they have to be kept alive through the aerosolization process, otherwise they won't be able to infect anything.
It's not impossible to do. Both the United States and the Soviet Union developed plague-aerosolization capabilities during the Cold War. But ISIS would need both people with such expertise and probably also a sophisticated laboratory where it could develop and test such a weapon without accidentally killing the experts creating it.
Professionals who work with aerosolized plague virus in the US are required to do so in a biosafety level three laboratory (out of four levels — four being the highest), which has special air filtration and requires personal protective equipment such as gowns and sometimes respirators.
There are limits to how much a plague weapon could do
Plague bacteria can be treated with antibiotics, although even early antibiotic treatment is not expected to save everyone with pneumonic plague.
Plague bacteria also don't last long in the air — about an hour, depending on the exact conditions — and can be killed by heat and sunlight. So it's unlikely that environmental contamination would be a problem contributing to its spread.
The main problem would be being near someone with pneumonic plague, that person coughing, and then those tiny droplets of plague getting into your lungs. "You really need close face-to-face contact to transmit with high frequency," Gage says.
There are known, standard hospital procedures to prevent such kinds of transmission in health-care environments. And people with known exposure to plague bacteria might be given antibiotics as a preventative measure.
"In a developed country, I think we can interrupt that chain of transmission through the use of appropriate masks and those sorts of things," says Gage. "That first wave of infection is really the biggest problem."
Should a plague attack ever happen, the CDC says it has antibiotics on hand that it can ship to wherever necessary within 12 hours.