There was an interesting interview with Microbiologist Jenny Rohn about how long we are contagious after an illness. She points out that it not only varies from virus to virus but also from person to person. That said, there are some general statistics that may help you avoid passing around an illness.
Common Cold: First, they aren’t common. There are many rhinoviruses, even if most of them have similar symptoms. If you have a cold, don’t go out the first day you feel better. You are still contagious for a day or two after the symptoms abate.
The Flu: There are going to be lots of variations to this, even more so than a cold. That’s because the virus mutates quickly. One thing that doesn’t change; you are contagious a full day before symptoms appear. You will remain contagious for up to seven days after symptoms appear. Children may remain contagious longer.
Measles: As the outbreak grows this is important information. You are contagious four days prior to the rash appearing and for four days after the rash appears. This disease is so contagious that 90% of those not immune will catch the illness from just one case nearby.
Strep Throat: If you have strep throat you are contagious until you’ve been on antibiotics for a minimum of 24 hours. Some are still contagious until 48 hours after antibiotics are in use. The most likely age range for strep throat is five years to fifteen years, but anyone can catch it.
There are other diseases, some with long contagious periods. A man who survives ebola can pass it along for up to nine weeks after recovery. It’s important to ask your doctor when you are ill so that you know how long to avoid contact with others.
There are other things you can do, both to prevent catching one of these diseases and to prevent passing it along. Two of the four mentioned have vaccinations available. As they can both have serious complications, it is recommended that you get vaccinated, especially if there is an outbreak in your community.
Many of these diseases are droplet spread. That means talking, sneezing, coughing and so on sends virus particles out for others to breathe in. Those who are ill should cough into their elbow rather than the hand. This could help prevent the spread.
Remember that stair rails, shop doors and grocery carts are touched by a lot of people. You don’t know whether the last person touching one of these items was ill or not. While I don’t generally recommend using antibacterial products, the cart wipes are a good idea.