Winter’s here, and you feel lousy: You’re coughing and sneezing; your muscles ache; your nose is an active mucus volcano. These symptoms — so familiar at this time of year — can mean only one thing: Tiny fanged snails are eating your brain.

No, seriously, brain snails are involved only about 35 percent of the time. More likely what you have is a cold or flu. (The word “flu” is short for “the flu.”)

Colds and flus have plagued humanity for millions of years, but in primitive times, nobody knew what caused them, because everybody was stupid. Then, in the 17th century, scientists began to suspect that colds were caused by a small creature called a “germ” living inside human nasal passages. But they never found it, although they searched relentlessly, using a painful procedure that involved a feared instrument called the “nostril torch.”

The big breakthrough came in the 1930s, when scientists invented a device called the electron microscope. At least they claimed they invented it. Laypersons would come around to look at it, and they’d say, “Where’s the electron microscope?” And the scientists would roll their eyes and — in the tone of voice you’d use to talk to a Labrador retriever — they’d say: “You can’t SEE it, for heaven’s sake! It’s made of electrons!” And the laypersons, out of pure embarrassment, would give the scientists funding. (This is also how scientists paid for the “radio telescope.”)

Using their electron microscope, scientists discovered that colds and flus are caused by “viruses,” which are invisible organisms that originate, via a process that biologists call “spontaneous combustion,” on doorknobs and Power Ranger action figures. From there they travel into a human body, where they reproduce via a process that biologists call “having sex.” Afterward they smoke tiny cigarettes (this is what causes fever) and then exit the human body by causing it to either sneeze or blow its nose, a process that biologists call “playing the snot trombone.”

Once out of the body, the viruses travel through the air, and — by a process that is still not understood — find their way, over thousands of miles of unfamiliar terrain, to a tiny area in the mountains of central Mexico.

No, sorry, that’s the monarch butterfly. The viruses just go back to the doorknobs and Power Rangers, where they lurk in wait for their next victim.

So we know how viruses operate; what we don’t know is how to kill them. After trying many unsuccessful methods, including tiny hammers, medical researchers determined that the only sure way to kill a virus is to heat it to 7,000 degrees. This led to an experimental cold-and-flu treatment known as the “microwave sauna,” which produced a 100 percent cure rate, but had the unwanted side effect of turning the patients into human corn dogs. At that point, medical researchers gave up on curing colds and flus, and devoted all of their efforts to making sure there is no available parking within 1,000 yards of any hospital. This is where we stand today.

But that doesn’t mean there’s no hope for cold and flu sufferers. Go to any drugstore or supermarket, and you’ll find a vast array of cold and flu products that, for your safety, you must stab open with a knife. These products work by attacking the cold or flu virus with large chemical names such as “acetaminophen,” “dextromethorphan,” “pseudoephedrine,” “phenylpropanolamine,” “diphenhydramine,” and “chlorpheniramine,” which, when they get into your bloodstream, break apart into smaller chemical units called “syllables,” which roam around until eventually your body turns them into fat.

Clinical studies show that if you take these products as recommended your cold will be gone in two to three weeks; whereas if you DON’T take these products, your cold could linger for as long as two, or even three, weeks. In other words, these products have no effect whatsoever, but you should buy them anyway, because otherwise the multibillion-dollar cold-and-flu-remedy industry will collapse, and there will be nothing propping up the economy except telemarketers.

But your best plan is to not get a cold or flu in the first place. According to the American Society of Medical Doctors Who Cannot See You Now, you should take these basic precautions during cold and flu season: 1. Drink plenty of fluids (“fluids” is the medical term for “beer”).

2. Remove all doorknobs from your home and office.

3. If you have children — especially small children who attend preschool with other small children — ship them to New Zealand.

Also, just to be safe, you should get a snail shot.

Dave Barry is a humor columnist for the Miami Herald.