According to the CDC, the flu virus can live on moist surfaces for 72 hours. The number one rule is not to share your toothbrush anytime, but especially when you are sick.
You don't necessarily need to replace your toothbrush after you’ve been sick. Unless your immune system is severely compromised, the chances of reinfecting yourself are very low. If you’re still in doubt, throw the toothbrush out especially if you’ve had your toothbrush for 3-4 months.
Read the label before you pick up a bag at the drug store with an eye to avoid ingredients like fructose or corn syrup. Many cough drops contain sugar, and it is like sucking on candy. Sugar is a culprit when it comes to cavities. The longer you keep a sugary cough drop in your mouth, the more time cavity-causing bacteria has to feast on that sugar, which produces the acid that can leave holes in your teeth.
One unfortunate side effect of a stomach flu, among other illnesses, is vomiting. You might be tempted to brush your teeth right away, but it’s actually better to wait. When you vomit, stomach acids are coming in contact with your teeth and coating them. If you brush too soon, you’re just rubbing that acid all over the hard outer shell of your teeth.”
Instead, swish with water, a diluted mouth rinse or a mixture of water and 1 tsp. baking soda to help wash the acid away. Spit, and brush about 30 minutes later.
When you’re sick, you need plenty of fluids for many reasons. One is to prevent dry mouth which can put you at greater risk for cavities. The medications you might be taking for a cold or flu—such as antihistamines, decongestants or pain relievers—can also dry out your mouth, so drink plenty of water and suck on sugarless cough drops, throat lozenges or candies to keep that saliva flowing.
When it comes to your mouth and your body, water is the best and safest beverage to drink. Sports drinks are recommended to replenish electrolytes when you are sick, but drink them in moderation because they contain a lot of sugar.
Also, avoid adding lemon or sugar to your cold or warm drinks. Sugar helps to fuel cavity-causing bacteria and lemon is acidic.