Please, please, please work from home.

It's cold and flu season, and you're already on high alert. You have a tickle in your throat, Janet in Finance is coughing all over the coffee machine, and someone on the subway just sneezed on you (yuck). (See: How to Avoid Getting Sick During Cold and Flu Season)

The common cold is particularly contagious, and can be more than a pesky nuisance that costs you a couple of sick days (or keep you form your workout). Let's take a look at how long a cold is contagious, exatcly, and how to keep from getting one in the first place.

How Long Is a Cold Contagious?

Pre-cold: Fun fact: Your contagion period starts before you even have symptoms. Specifically, you can share cold germs one day before symptoms begin, according to Rajsree Nambudripad, M.D., an integrative medicine specialist with St. Jude Medical Center in Southern California.

Mid-cold: You could have light symptoms or you could feel like you're ~literally~ dying. Either way, if you're symptomatic, you're contagious.

"If you're having low-grade fevers, body aches, headache, sore throat, cough, nasal or sinus congestion, then it's safe to assume you're contagious!" said Dr. Nambudripad.

Post-cold: You're period of contagiousness continues five to seven days after your symptoms begin, even if the symptoms have subsided. This means that during cold and flu season, those who don't even know they have the cold virus can spread it to you. Scary. (More here: The Step-By-Step Stages of a Cold—and How to Recover)

Also, that coworker with a cold who said they don't feel too bad and came into work anyway? They're likely still contagious—they just have a stronger immune system. "Some people with strong immune systems do not come down with full-blown colds," said Dr. Nambudripad. "They just have slight body aches for a day or so. But because their body is still fighting an infection, they may still be contagious, and may be able to spread the virus during that time frame."

This is why it's always a good idea to stay home and rest to prevent the spread of the virus to others. And, of course, to recover.

If You're Super Sick, Are You Super Contagious?

Not necessarily. Though excessive coughing and sneezing certainly increases the rate at which you spread bacteria particles, you're not any more contagious if you're feeling extra crummy.

"The severity of your symptoms is often a reflection of your immune system, rather than the severity of the virus," says Dr. Nambudripad. "The same virus can cause completely different symptoms in different people. What might be a minimally bothersome cold to you may become severe viral bronchitis in an immunocompromised or older person." (But maybe make sure you have a cold and not the flu...and if you do have the flu, here's how long it will last.)

That said, if you're feeling particularly run down, it's probably a good idea to see a doctor. Specifically,  you should consider seeing your primary care doctor, "if you develop a fever, localized pain in your ears or sinuses, or if your symptoms last for more than a week without getting better," says Bertie Bregman, M.D., NYC family medicine doctor and co-founder of Qwell.

How Is the Cold Virus Spread?

Seeing as how most common cold symptoms result in you launching bacteria into the space around you (coughing and sneezing), it's easy for the cold virus to spread through the air. "You can spread common upper respiratory viruses through respiratory droplets when you sneeze or cough, so be sure to cover your mouth with your elbow when you cough or sneeze and wash your hands frequently," says Dr. Nambudripad. "Sometimes it's helpful to cough into a scarf or tissue to prevent spreading infected respiratory droplets to your coworkers." (Ahem: How to Sneeze Without Being a Jerk)

The common cold isn't just transmitted through air particles. "Anything that has saliva or respiratory droplets can be contagious," says Dr. Nambudripad. "That's why it is important not to share cups or utensils." That goes for kissing, too (obviously). "Also be sure to disinfect and wipe down any shared computer keyboard, mouse or phone, and wash your hands before shaking hands or touching other people." (Here's exactly how long cold germs can survive on things like doorknobs and subway poles.)

How Can You Prevent the Spread of a Cold?

It's easier than you might think. "Strengthen your immune system and follow basic contact precautions," says Dr. Bregman. In terms of fortifying your immune system, start with the basics. "Make sure to get enough sleep and exercise, and eat a healthful diet full of fresh vegetables." (Try these 12 foods that boost immunity.)

And please, wash. your. hands. "Washing your hands or using hand sanitizer periodically—and after you have come into contact with someone who has a cold—is a good idea," says Dr.Bregman. "But no need to go overboard; being exposed to everyday germs actually builds your immunity." (See: How to Clean Your Skin Without Getting Rid of Good Bacteria)

Clean your workspace and disinfect any shared areas (especially keyboards and phones), and keep a nice distance from people who may be contagious. While traveling, try not to touch the TSA bins, as they're rife with respiratory viruses and bacteria. (And do all these other things to boost your immune system.)

If you start to feel symptoms, act immediately. "The first thing you should do the second you feel a hint of illness is to drink plenty of water, get rest and sleep, and take some immune-boosting supplements that can help your body fight viruses," said Carrie Lam, M.D., a board-certified family medicine doctor in Loma Linda, California. "These steps can protect against illness and reduce the severity once it starts."

Above all, keep germs to yourself (read: stay in bed and work from home, please). "The best thing you can do is stay home and rest," says Dr. Nambudripad. "You will be doing yourself and your coworkers a favor." Ask for work from home days for the sake of public health.

But if you absolutely have to go out in public, "be sure to cough and sneeze into tissues and wash your hands frequently," she said.