Andrew Kelly / Reuters

October, as it turns out, is not an optimal time to start sealing yourself into a tin can of humanity twice a day after years of riding the subway only occasionally.

I just got a new job at The Atlantic, and before that, I worked from home. Writing online doesn’t necessarily involve a lot of leaving the house, and most of the friends I see regularly live within walking distance of me, so for the past two years, I was, at most, a very occasional public-transit user. Because The Atlantic is an august establishment with an office and free snacks, starting this job meant I’d have to return to the subway-commute schedule that I abandoned in 2016.

Silently, I braced for the cold I feared that might bring, should my stay-at-home immune system not adjust quickly enough to its get-on-the-train future. And then, for a week, I took Amtraks and subways and shook hands with many incredibly kind strangers, all ready to welcome me into their professional lives.

Reader, I got a cold. And then I got this assignment.

The idea that public transportation will make you sick is an incredibly durable bit of pop-science wisdom, especially when you consider the relatively meager actual data on the topic, according to Stephen Morse, a professor of epidemiology at the Columbia University Medical Center. He says I was right that my newfound commute was a potential culprit, but not necessarily because of its newfoundness.

“I think it’s fair to say that in general, the flu and colds and other things are spread person to person,” Morse told me. “There’s no question that the more contact you have with people, the greater likelihood you are exposing yourself to infection. If you are a hermit and presumably have no contact with people, you are at very low risk.”

As with so many things in my past, leaving my house, in general, is probably where I went wrong. Before we get too finger-pointy at the subway, though, Morse cautions not to assume causation where mere correlation might be at hand. The main risk factor for contagion is proximity to other potentially sick people, no matter whether those people are on the train, in your office, or standing in line to get a lunchtime chopped salad just like you. So all those smiling faces, welcoming me to my new job with a firm handshake? One of them could have very easily been patient zero for my clogged sinuses, and how I got from my apartment to their cubicle or conference room wouldn’t have mattered at all. Cold and flu season is other people.

And in temperate regions like the northeastern United States, it really is a season—tropical and subtropical areas don’t experience the winter-specific cold and flu explosion that places with cold winter weather typically have, according to a 2016 study. So my big mistake might not have been getting on public transit or meeting my new coworkers, but instead, doing all that in the first chilly month of the year in New York. There have long been theories about why cold weather is a breeding ground for rhinovirus. It could be because you socialize more in close quarters when it’s cold out. A 2017 study from researchers at Yale University suggests the decreased temperature itself could be to blame. The study was conducted on mice, but it found that even a 7-degree dip in temperature was enough to suppress their natural immune response to infection.

If you’re feeling immunologically smug because you’ve been riding public transit to work every day for years and assume that’s built up your general resistance to illness, I hate to burst your bubble, but you have the same likelihood of coming down with the sniffles on any given day as anyone else who ventures along a similar path. People in this situation might be conflating their supposed resistance to the common cold with the hygiene hypothesis, according to Morse, which is the idea that allergic and autoimmune reactions are made worse when people are kept away from irritants, depriving their immune systems of the chance to build up a response. “The evidence on that is mixed,” Morse says. “And with colds and viruses, there are so many of them. If you ride the subway often, you’re likely to be exposed to more of them, and you may be getting colds more often.”

My two-year break from office work had not put me at an elevated risk for infection when I left the house—it had actually insulated me from a lot of small, daily potential exposures to illness. But now I have this job, which has been great so far, with the exception that getting to it requires me to star in my own low-budget remake of Contagion. Is there any way to fight back against the necessary health scourge of my own career, beyond becoming an independently wealthy and mysterious recluse? I spoke with Katherine Harmon, the senior director of category intelligence at the risk-management firm WorldAware, to see what she’d advise for both employers and employees looking to mitigate cold-weather risks. She told me to use hand sanitizer after I touch elevator buttons, and although I hadn’t ever really thought about how dirty those probably are, now I will think of nothing else for the rest of my life.

But according to Harmon, the biggest differences can be made by employers. “Making sure that people stay out an appropriate amount of time when they’re feeling ill is probably the single most important thing a company can do,” she says. And the best way to do that is for employers to let sick people take the time off they need and to let people work from home, in jobs where that’s feasible. (Lucky for me, I’m in one of those jobs.)  “If somebody says they’re sick and they know they can work from home, there’s less of a risk of ‘presenteeism,’ which is when people who are sick come to work anyway because they’re obligated to be there,” says Harmon.

So if you want to stay healthy during cold and flu season and help others do the same, the answer is pretty simple: Stay home when you don’t feel well if at all possible, and bully (okay, “encourage”) your sniffly co-workers to do the same. You might not just be saving yourself, but also saving a woman on your train who doesn’t yet know the procedure to get permission to work from home at her new job.

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