7 cold virus and flu myths and questions debunked

A rundown of what doctors and scientists recommend to prevent and treat the common cold during cold and flu season.

People assume a cold will be gone within a few days, but doctors disagree

For most people, a cold lasts seven days. But colds can also trigger attacks of asthma and other serious respiratory illnesses. (BSIP/UIG/Getty)

Early sunsets and chilly temperatures signal a shift from the itchy, watery eyes and sneezing associated with pollen allergies to the runny noses and coughs of winter cold and flu season.

But just how long should these respiratory bugs last? And how long are you contagious? Here are some answers.

Are coughs from colds lasting longer now than before?

Probably not.

"What I see doing pediatric clinics is that once a child gets a cold-like illness, like a runny nose and cough, is that people presume that it will all be gone within a couple of days," said Dr. Jonathan Gubbay, a medical microbiologist and pediatric infectious disease physician in Toronto.

That's not exactly right.

"For most of us, it's a seven-day thing and it's gone," said David Proud, a professor of physiology and pharmacology at the University of Calgary. "We whine and complain, but [the cold infection] is really self-limiting."

Proud studies people infected with cold viruses as part of his research into how colds can trigger attacks of asthma and chronic obstructive pulmonary disease (COPD). He said that in a "tiny" percentage of people, colds can have side-effects such as otitis media, or middle ear infections, which can be worse in those with a tendency to sinusitis.

How long are people infectious?

Gubbay said people are infectious for the first few days after symptoms start, particularly the period with a fever. Health guidelines generally recommend keeping kids home from school until the fever is gone for 24 hours.

What treatments are recommended?

"The old joke that we have is, you can take all the best available current medications to treat it and it'll go away in a week. Or you can do nothing and it will go away in seven days," Proud said.

The reason, Proud said, is there's not much clinical trial evidence, which is the gold standard, to tell if over-the-counter cold medications help.

Hand hygiene is key to preventing the spread of cold and flu germs. (Photo illustration by Ute Grabowsky/Photothek/Getty)

Even so, fever can be uncomfortable for children and adults and fever reducers can help, said Dr. Michelle Murti, a public health physician and Gubbay's colleague at Public Health Ontario.

"Warm, hot liquid can help make the mucus less sticky and help it drain a little bit better," Murti said. "That's why having that steam or a nice hot water or hot tea can be a soothing thing."

Murti added that honey can also help with coughs. One important caution: Children under the age of one shouldn't have honey because of the risk of botulism.

Cold vs. influenza

Murti said adults don't tend to get a fever with a cold. Now that flu season has begun in every province and territory, if an adult has a fever and cough that comes on suddenly, consider influenza.

At the end of December and early January, Murti said Canadians will probably see more flu, with a sudden onset of cough, fatigue, muscle aches and "feeling like you got run over by a truck."

Health officials recommend flu vaccines. "That's really the best prevention measure that we have," she said.

Gubbay said lab testing for influenza isn't recommended for patients outside of the hospital, because it takes days to get the results, which is too late to decide on giving patients antiviral medications.

What about coughs after colds?

OK, you're no longer going through boxes of tissues. But then the cough sets in … and keeps going.

"We have a physician here who has a chronic cough clinic precisely because … people don't really understand, if you've never experienced it, how miserable it can make life," said Proud, who also holds the Canada Research Chair in inflammatory airway diseases. "It's actually quite irritating for people, to say the least, not to mention disruptive."

No one knows why such coughs occur. "We think it may have something to do with [people's] nerves and their sensitivity to various kinds of irritants, but that's really not much more than an educated guess," Proud said.

Gubbay suggested saltwater sprays or drops can help dry up the nose to prevent such coughs.

The good news is that after a couple of weeks of a prolonged cough, people generally aren't infectious, because they're not bringing up the same level of virus as earlier, Murti said.

When is a cough more serious? 

Murti said concerning symptoms of a cough include:

  • Coughing to the point where you can't breathe.
  • Throwing up from a cough.
  • Difficulty with underlying respiratory conditions, such as asthma or COPD.

A prolonged, more severe, wheezing cough could be from whooping cough, also called pertussis, a bacterial infection.

Gubbay said respiratory illness in an infant, particularly in the first few months, is worth having checked out by a health-care practitioner. Ditto for a fever in an older child that's lasted more than 48 hours, or if there are symptoms beyond a runny nose and cough. These include looking lethargic with low energy levels, breathing quickly or requiring a lot of effort to breathe.

How to prevent spread

Murti said cold viruses can last on your skin, including your hands, for a couple of hours after a cough or sneeze. That's why it is important to wash your hands with soap and water often in the first five to seven days of a cold, and to use hand sanitizer. 

Public health experts also recommend sneezing into the elbow of your sleeve instead of your hands.

With files from Amina Zafar