Flu is the holiday ‘gift’ nobody wants. Here are strategies to stay well.

If it seems as if everybody you know is coughing and sneezing or moaning about flu aches, you’re not imagining it, infectious disease experts said. But you can’t blame your holiday visitors for bringing their flu viruses along with them; federal health officials say elevated levels of flu-like illness are happening all over the country.

Flu activity, as officials call it, is now considered widespread and rising. And along with influenza viruses, respiratory syncytial virus (RSV), and 100 varieties of cold-causing rhinovirus come out to party — just as we do.

Some of this has nothing to do with the holidays. These bugs thrive in cooler, drier winter air. ‘Tis their biological season.

So a lot of us would get sick in December or January even if our friends and family weren’t giving viruses a free ride from, say, Dallas or Chicago or Paris to Philadelphia International Airport and then into our dining rooms.

» READ MORE: Does the cold make you catch a cold? The truth on 7 common beliefs about germs

Are we doomed or are there ways we can protect ourselves from that sick guy on the plane or that runny-nosed nephew?

The single best thing you can do to protect yourself from flu is to get a flu shot, experts agree. The shot is only about 60% effective against getting sick but it does reduce symptoms if you do catch something, which means it is better at preventing hospitalizations and deaths. Even if you’re healthy and the flu is more of a nuisance than a serious threat, getting a shot can protect babies too young for inoculation and other people whose weakened immune systems prevent a strong response to the shot. That includes people with cancer and the elderly.

As of mid-December, reports the Pennsylvania Department of Health, 144 flu-associated hospitalizations and seven flu associated deaths have occurred so far this season.

Yet lots of people don’t get the flu shot and there are no shots against RSV and cold viruses. RSV is underappreciated as a danger for children and older adults. All these germs are spread through droplets in the air that sick people expel with coughs and sneezes. We get sick by breathing them in or, more often, touching something contaminated and then touching one of the viral portals on our face: the eyes, nose, and mouth.

Anne Norris, an infectious-disease specialist at Penn Medicine, said that colds tend to be the lead-off hitter in the fall-winter viral onslaught. You can thank the return of young children to school for that. Kids, she said, spread the highly contagious virus through “direct contact with basically snot on the fingers.” When it comes to rhinovirus, which causes more than half of common colds, “children are clearly the vectors,” she said.

Flu tends to start later, with the average flu season lasting 13 weeks between December and March. Currently, Louisiana is the only state reporting high activity. The Centers for Disease Control and Prevention report minimal flu in New Jersey and Pennsylvania. RSV and flu often coexist. (You’ll probably know you have flu because it hits fast and hard with aches and fever. The respiratory symptoms tend to be less pronounced than in a cold or RSV.)

Norris said planes are not as bad for spreading germs as many fear. Ventilation systems have improved and studies have shown you’re most at risk if you are sitting directly beside or in front of someone who’s sick. Some people, she said, recommend choosing a window seat because you’re exposed to fewer passengers there than in an aisle seat.

She always leaves the overhead air on to improve air circulation. Yes, that can make her seat frigid, so she also always brings socks, a sweater, and a blanket.

Kevin Morgan, a nurse practitioner with MinuteClinic in Center City, goes a few steps further. He said germs can live for hours on surfaces that might not be thoroughly disinfected between flights. He recommends travel packs of disinfecting wipes to clean the tray table, arm, and headrests, and seatbelt buckles. At your hotel, wipe down the TV remote and light switches. A travel-size bottle of hand sanitizer is also a good idea, he said.

Many holiday travelers take long trips on buses and trains this time of year. Transmission is not as well-studied on those forms of mass transit, but you’re clearly at higher risk when packed in with lots of other people than you are in a room by yourself.

As for the sick travelers who show up at your house, well, science mostly fails. As Daniel Mueller, an infectious-disease doctor at Temple University Hospital, puts it: “You’re not going to tell grandma or grandpa to go back home.”

Norris also sees little way out, except maybe keeping some physical distance between you and a sick guest. “You’re socially constrained here,” she said, “but I would avoid prolonged face-to-face contact with someone who was expelling infectious particles.”

If you’re pretty sure you’ve been exposed to flu, Norris and Mueller said, your doctor might be willing to prescribe a prophylactic dose of an antiviral medicine such as Tamiflu.

Even if you manage to avoid germs from fellow travelers and guests, these pathogens are everywhere. The grocery store. The day-care center. The mall. And, the office.

A new economic paper from researchers at Emory and Ball State Universities and the University of Alabama-Birmingham found that higher employment and flu transmission rates go together. A 1% increase in the employment rate correlated with a 16% increase in influenza-related doctor visits. The trend was strongest in the retail and health-care sectors, where there is a lot of interpersonal contact. (There was no change among construction and manufacturing workers.)

This brings us to what sick people can do for the rest of us. First of all, stay home if you’re sick, particularly if you’ve got a fever over 100 degrees or so. Wait till the fever has been gone a day to interact with healthy people. People are less likely to stay home with colds, which typically don’t cause fevers, but Norris wishes they would. “They’re leaving rhinovirus all over the place for the rest of us,” she said.

If your job has skimpy sick days or a culture of show-up-no-matter-how-bad-you-feel, then at least try to protect the common air and surfaces by coughing into your arm or shoulder. Throw your tissues away after one use. Use hand sanitizer every time you blow your nose. Take a cough suppressant. You could even wear a surgical mask.

We can all try not to touch our faces. Good luck with that. Norris said there’s no good evidence that extra vitamins will help most of us ward off infection.

The best source of protection is easy and cheap: Wash your hands. A lot. Wash them after using the bathroom. After flying. After riding a train or bus. After shopping. Especially before you eat.

“In every study of every kind,” Norris said, “hand-washing makes a difference.”