Campaigning at the best of times takes a toll on the body. Between the lack of sleep, poor diet, and stress — not to mention hand-to-hand exposure to hundreds of strangers every day — keeping a candidate healthy is always an uphill battle.

That was the case before the novel coronavirus reshaped American society and politics. Now, with a global health emergency at our door and the three main presidential candidates remaining all in the highest-risk age group (Joe Biden, Bernie Sanders, and President Trump are all in their 70s), the lifestyle of a politician is even more risky.

Huge amounts of a campaign present problems in the context of a pandemic — for the politician, his campaign and his supporters. Both the Biden and Sanders campaigns canceled rallies in Ohio this week, but that could only be the first of many changes.

Coronavirus spreads through close contact with infected people, and the Centers For Disease Control is recommending people in high-risk groups, including older adults, avoid things like close contact with strangers and large gatherings. In other words, all that hand shaking and baby kissing is not ideal. Huge, crowded rallies where a septuagenarian leans in close for photos with hundreds of strangers is a huge risk.

“It’s the antithesis of the recommendations,” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center. “However, it’s important to remember that these are recommendations. Nobody expects these recommendations will apply 100 percent of the time to 100 percent of the people.”

Schaffner said everyone should evaluate the importance of an event before attending. His wife, he said, has stopped going to bridge club, for example. The candidates, however, are playing a game with slightly higher stakes.

“It must be obvious that our political leaders — whether they’re the Democrat candidates or the White House — consider political activity pretty essential,” he said. “I trust that their aides are giving them lots of good hand sanitizers because there’s a lot of gripping and grinning that goes on there.”

All that gripping and grinning puts candidates and their staff at risk. Research has shown that shaking hands is an extremely effective way of transferring microbes. In a 2014 study, researchers found that shaking hands transferred 10 times more microbes than a fist bump when they tried the different greetings after dipping their gloved hands into E. Coli. And the more people a candidate is interacting with, the higher the risk of infection, Schaffner said. “Your chances of catching a fish increase the more times you throw your line into the pond.”

But those hand shakes are a huge part of a daily campaign. Erick Sanchez, who worked as traveling press secretary for former candidate Andrew Yang, said the Yang campaign would regularly stop at four to five events per day, and that Yang would end up shaking “hundreds” of hands a day.

“I’m a firm believer — and I feel like a lot of folks in the industry are firm believers — that these types of conversations are helpful,” Sanchez said, pointing to public Q&A events and local press briefings as key to a campaign.

Even when politicians aren’t campaigning they’re at risk. Several Republican politicians put themselves in self-quarantine in the past week, after someone who had attended last month’s Conservative Political Action Conference tested positive for coronavirus.

Also, a campaign has to think about more than just the candidate’s wellbeing. Anyone attending large gatherings where they’ll be in close contact with strangers in an area where coronavirus is spreading is at risk of infection. It’s why Ohio’s governor asked for groups to consider cancelling large gatherings, a request the campaigns decided to heed, or why people who attended business conferences where an attendee later tested positive for the virus have voluntarily offered to isolate themselves. Campaigns that continue to host mass gatherings, whether attended by the candidate or not, are putting their supporters’ and their communities’ health at risk.

There are also many other campaign functions that depend on increasing person-to-person contact — indeed, that’s the point of most of them. “Beyond just those in-person rallies, you’re thinking about things like canvassing. Is it safe for canvassers to be out knocking on doors? It pretty much affects most pieces of the operation,” Sanchez said.

For now, both the Biden and Sanders camps are being cautious about making predictions for future campaign events, saying they will consult with public health officials and make calls on a case-by-case basis. Trump has also refused to stop shaking hands with the public amid the outbreak (even though the self-proclaimed germaphobe has previously talked about how easy it is to catch infections in this way and called handshaking “barbaric”). But as coronavirus continues to spread, more local health officials and politicians may follow Ohio’s lead.

“It’s probably not the worst thing in the world for septuagenarian candidates to cut back on rallies and travel,” said Lis Smith, the senior communications advisor for former candidate Pete Buttigieg, who also spoke out this week about rethinking campaign norms during an outbreak. “But now the hard work will fall to campaigns to figure out how they reach voters. This is a moment without precedent and it will be interesting to see what campaigns rise to the challenge of meeting it.”