Is it true that colds and flu are most contagious before symptoms appear?

The BabyCenter Editorial Team

People are sometimes contagious before they show symptoms of a cold flu, although that may not be when they're most contagious.

Depending on the virus causing the illness, you may be contagious before you even know you're sick – a day before coming down with symptoms, for example. In other cases, you'll be well aware of your illness before you have the opportunity to pass it along.

With some viruses, you're contagious for as long as you have symptoms or even beyond. With others, you continue to have symptoms after you’re no longer contagious.

Adults who have the flu are contagious for five days after first developing symptoms, while kids can stay contagious even longer. If you have a cold, you're most likely to give it to someone else during the first few days of having a runny nose, sneezing, and coughing.

All of this points to the importance of practicing good hygiene – including frequent hand washing – even when everyone seems perfectly healthy.