Overview: Whether you have a common cold, virus, bacterial infection or influenza, it's important to know how long you're contagious for your own health and the safety of others.
When it comes to being sick, we’ve all heard someone say, “Don’t worry, I’m not contagious anymore.” However, they may still be spreading germs even after their symptoms pass. Understanding the different contagious periods will help you feel confident about keeping you and your loved ones healthy.
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What is a contagious period?
A contagious period is the timeframe an illness is transmittable from one person to another.
The incubation period, or time before symptoms are visible, can differ among illnesses and affect the contagious period. While you, and the people around you, may not have symptoms, you may still be contagious.
You can help yourself and others stay healthy with frequent handwashing, keeping physical distance between yourself and others, regularly disinfecting surfaces and covering your cough and sneeze. If you're actively ill and contagious, consider wearing a mask to prevent the spread of germs.
Viral vs. bacterial infections
When you feel ill, you should be tested by your primary care provider to diagnose whether you have a virus or a bacterial infection to ensure you're prescribed the correct treatment plan.
Viral infections: Viruses are small germs that use your cells to reproduce.
When you have a virus, you'll not be prescribed antibiotics, as they only kill bacteria and won't work on a viral illness. Rest, fluids, over-the-counter pain and cold medicine and time to recover are the best prescription for returning to good health. For Covid-19, anti-viral treatments are helpful if started in the first few days of experiencing symptoms.
Common viruses
Common cold (rhinovirus):
- Symptoms come on gradually, and you can spread this virus one to four days before you feel sick. These may include a runny nose, sore throat and mild fever.
- When you have a cold, you’re most contagious during the first few days when your symptoms are at their worst.
- You’ll remain contagious if your symptoms are present, which could be two weeks.
Influenza A and B:
- Influenza (flu) A infects humans and animals, while flu B only infects humans.
- Symptoms are similar, with sudden high fever, chills, cough, sore throat, muscle aches and fatigue.
- Flu A peaks in fall and winter, and flu B usually peaks in late winter and spring.
- Flu A changes rapidly from year to year, but flu B mutates more slowly.
- An annual flu shot protects against both strains.
- The incubation period for flu A and B ranges from one to four days, and the contagious period can last up to two weeks.
- You’re most contagious during the first three to four days when your symptoms are at their worst.
Norovirus and rotavirus:
- Both viruses are often referred to as “stomach flu.”
- Norovirus is more common in adults, and rotavirus in children.
- Symptoms of norovirus and rotavirus include diarrhea, vomiting, nausea and stomach cramps.
- With norovirus, you’re contagious 10 to 50 hours before you experience symptoms and remain contagious for up to three weeks.
- With rotavirus, you’re contagious for 24 to 72 hours before experiencing symptoms and remain contagious up to three weeks.
Covid-19:
- You’re contagious period starts one to two days after exposure and lasts up to 10 to 20 days.
- This virus is different than others, in that some people have no symptoms, while others may become very ill. Symptoms often vary and may include fever, cough, shortness of breath, congestion, body aches, headache, sore throat, loss of taste and smell, nausea, vomiting and diarrhea.
- The CDC recommends isolating until your symptoms improve, and you’ve been fever-free without medication for 24 hours.
All of these viruses are spread through airborne droplets that come from things like a cough or sneeze, which are then left on surfaces. This is why handwashing is vital to helping you stay healthy.
Bacterial infections
Bacteria are harmful, single cell microorganisms that multiply and damage your body. Bacterial infections include strep throat, urinary tract infections (UTIs), skin infections, pneumonia, bronchitis, conjunctivitis (pink eye) and others. When you have any infection, you'll be prescribed antibiotics to kill the bacteria.
Some infections aren't spread by human contact. However, there are several that spread from human contact or contaminated surfaces. Infections like pneumonia or sinus infections aren't contagious themselves, but the symptoms leading up to those illnesses can spread and make you ill.
Once you're prescribed antibiotics, your contagious period shortens to just a few days. Even if you begin to feel better on the medication, it's important to finish the entire prescription, because stopping early can allow the bacteria to bounce back in your system.
Bacterial infections spread through:
- Air or droplets: Contaminated dust, droplets of water or mucus
- Direct or indirect contact: Skin, mucus or contaminated surfaces
- Vector: Mosquito, tick or flea bite
- Vehicular: Contaminated food or water
Protect yourself and others
Whether you've been diagnosed with a viral or bacterial infection, it's important to follow the treatment plan recommended by your provider. To avoid becoming ill, resting, maintaining good nutrition and hygiene habits help to support your immune system.
At the first sign of symptoms, schedule an appointment with your primary care provider for a diagnosis and get back on the road to good health.
This blog was medically reviewed by a MercyOne provider.
