The US military has been hit with coronavirus for the first time.

In a statement released Tuesday night, the US military command in South Korea announced that a 23-year-old soldier has contracted Covid-19, the disease caused by the new coronavirus. The service member was stationed at Camp Carroll near Daegu, the epicenter of South Korea’s major outbreak.

Since the soldier visited other locations before being diagnosed with coronavirus, US military officials in the country are checking to see if others have been exposed.

In the meantime, the statement notes, the US military is “implementing all appropriate control measures” to curb further infections among the ranks since the risk level remains “high.”

A USFK soldier stationed at Camp Carroll tested positive for COVID-19, marking the first time a U.S. service member has tested positive for the virus. We’re implementing all appropriate control measures to protect the force. https://t.co/kkfEIuW7Jb — U.S. Forces Korea (@USForcesKorea) February 26, 2020

This is a troubling development, not just for the soldier who has contracted the disease but for US troops stationed in South Korea.

The roughly 25,000 service members deployed there work with their counterparts in the country to improve the military-to-military relationship, but mainly to deter a potential invasion from North Korea. A weakened force is less able to do both of those things.

The news is also a scary moment for the hundreds of thousands of US service members around the world. America’s military might has little power against viruses, and in fact, the many hours spent in close quarters makes the US armed forces quite vulnerable to contagion.

That’s worrying, especially since a military heavily impacted by an outbreak will struggle if called upon. “Historically, infectious diseases radically impact military forces and can result in suspension or cancellation of military operations,” four experts wrote in the medical journal Clinical Infectious Diseases in 2007.

That’s precisely why no one should want the US military to lead a pandemic response, Ron Klain, who took charge of America’s Ebola response in the Obama administration, told me last year. If they do, and many get infected dealing with sick people, then the number of active troops starts to drop quickly.

What’s more, the armed services aren’t necessarily equipped or fully trained to deal with outbreaks. “Troops volunteer to take on great risks, but they don’t sign up to fight diseases,” Klain told me at the time.

Importantly, this infected soldier is abroad in South Korea, and it appears appropriate measures have been taken to minimize risks — but the potential threat to the US homeland remains.

If other service members in the area are contagious but don’t know it, they could bring coronavirus stateside to an American installation, or even to their homes as they visit family. At that point, the growing coronavirus crisis in the US might get worse.

It’s a good thing the US military in South Korea not only identified an infected service member but also informed the public of the situation. The concern, though, is that it may be just the first notification of many to come.