The length of time you're contagious for after having a viral infection depends on the type of virus involved. You can often spread the infection to other people before you start to feel unwell or notice a rash. The length of time that you can spread bronchitis varies, depending on its cause. In most cases, bronchitis is caused by the same viruses that cause the common cold or flu, and you're likely to spread the infection as long as you have cold or flu symptoms. You can spread
chickenpox from 2 days before the spots appear to until they have crusted over, usually 5 days after they first appeared. You can spread the common cold from a few days before your symptoms appear until all of the symptoms are gone. Most people will be
contagious for up to 2 weeks. Symptoms are usually worse during the first 2 to 3 days, and this is when you're most likely to spread the virus. If you have coronavirus (COVID-19), you can spread the virus to other people for up to 10 days from when your infection starts. But many people will no longer be contagious to others after 5 days. You can spread flu from 1 day before your symptoms start and for a further 3 to 7 days. Children and people with lowered immune systems may be contagious for a few days longer. Glandular fever is usually spread through direct contact with saliva, which is why it's sometimes called "the kissing disease". You can spread the infection from up to 7 weeks before you get symptoms until the symptoms are gone. There's no reason not to continue to go to school or work if you feel well enough. Symptoms of measles appear around 10 days after you become infected. You're most likely to spread measles from when your first symptoms appear to 4 days after the rash develops. First symptoms of measles include: Around 2 to 4 days later, a spotty rash develops that normally fades after about a week. MumpsMumps causes your salivary glands to swell. These glands are just below and in front of your ears. You're most likely to spread mumps from about 1 to 2 days before your glands swell until about 9 days afterwards. Rubella (german measles)People with rubella should stay off school or work, and avoid contact with pregnant women where possible, for at least 5 days after the rash first develops. ShinglesYou can't spread shingles to others. But people who haven't had chickenpox before could catch chickenpox from you. You can spread the infection while the rash oozes fluid. TonsillitisTonsillitis itself isn't contagious, but the viruses that cause it are. The length of time you can spread it will depend on the virus. Further information
Page last reviewed: 12 September 2022
 Editor's note: We've updated this popular flu and cold Q & A from December 2015 because, well, good advice is timeless. With flu season approaching and cold season already well underway, how can you dodge viral infections or limit their spread to colleagues and loved ones? For tips, we again turned to Dr. Steve Pergam, assistant member of the Vaccine and Infectious Disease Division at Fred Hutchinson Cancer Research Center and director of infection prevention at Seattle Cancer Care Alliance. He updated his advice from last year, took a strong stand on getting the flu vaccine and helped bust some common cold and flu myths, such as: 1. Can you catch a cold from being cold? I don’t think there’s any data to support that. It has more to do with being indoors, congregating in close proximity. Plus the winter season is when many major respiratory viruses circulate in the U.S., like influenza A/B and respiratory syncytial virus, or RSV, the cause of “croup” in young kids. 2. Is it true that people are most contagious before they know they’re sick? Respiratory viruses are best engineered to spread when you have physical symptoms. So the more symptomatic you are — the more you sneeze and cough — the more likely you are to spread an infection. You ever watch a sneeze in slow motion? I am a big fan of this video, which gives you a sense of what happens and all the particles you produce with a sneeze. That said, viruses are clever: You can shed virus that can infect others even when you are asymptomatic. 3. So how long are people contagious? For influenza, it’s one day before symptoms, and five to seven days after the onset of symptoms. It can be as long as 10 days. Young children and patients with altered immune symptoms can shed the virus for longer periods of time. Influenza can shed for months in high-risk bone marrow transplant recipients. 4. If you have just a mild cold, are you less infectious? Just because you have mild symptoms doesn’t mean the virus is mild. It may just mean that your immune system controls the infection. So it’s important to remember that even with minimal symptoms, YES, you can still infect others. Many of these “mild colds” can make other people really sick, especially if they have weakened immune systems. As I often tell people, a simple cold is rarely simple in high-risk patients. 5. What is the general radius that people can spread their cold or flu germs? If I’m in a work pod three feet from someone with a cold, am I toast? When you sneeze or cough, you’re producing thousands of particles of a size that can transmit influenza. A study done
at Wake Forest School of Medicine looked at the distance sneeze and cough particles can travel. It was about 6 feet. To infect someone, these particles don’t have to be breathed in, they just have to get into any mucosal surface — eyes, mouth or nose. In addition, drops spread by getting on surfaces such as door handles. That’s one of the reasons we tell people to cover their mouths when they cough or sneeze and to wash their hands frequently. Also stop touching your face!
Cough or sneeze into the crook of your elbow or preferably into a Kleenex, which you toss, and then wash your hands afterwards. If you sneeze into your hand and then touch something, you can spread the virus. I also encourage people to just stay home when they’re sick — the more you limit exposures, the less likely you are spread the virus.
7. Hands are bad, right? Washing your hands or using alcohol-based hand gel is a cornerstone of respiratory virus prevention. Your hands touch elevator buttons, public transport rails, all the different places you go on a daily basis, then you touch your face hundreds of times a day. I have a bottle of hand gel with me at all times. You can’t stop yourself all the time, but be more aware of whether your hands are clean before you start rubbing your eyes. 8. How far does avoiding touching bathroom doors get you? Although it’s probably less critical for respiratory viruses, it is important to prevent the spread of other diseases such as Norovirus, a gastrointestinal virus that leads to diarrhea and vomiting and is aptly known as “Winter Vomiting Disease.” You never know whether the person before you washed their hands or not. If you ever watch anyone wash their hands, it can be quite cursory. Sometimes they don’t even use soap or take just three seconds. Whenever you can, when you’re washing your hands, use a paper towel to turn off the sink, open the door, and then toss the towel away. That’s the ideal. 9. How long should you wash your hands? I’ve heard you should sing “Row, Row, Row Your Boat,” but I suspect I sing it too fast. Try “Happy birthday to you.” Sing it twice. Most people rub two hands together and think they’re done. We miss our thumbs, our wrists, under rings and jewelry, under fingernails, the backs of our hands. There are multiple steps. There are videos out there that show you how to wash your hands. It’s the same with hand gel. Make sure you get enough hand gel to cover your hands. 10. What about facial masks? Do they help at all? Although you often see people wearing a mask in public places to avoid getting the flu, it’s not clear that it provides a lot of benefit. We recommend that patients with active symptoms wear them in the clinic to prevent spreading respiratory droplets. But you have to wear them correctly. And their effectiveness is limited once they get wet from coughing, sneezing or the humidification in airways. Update: Masks and Respiratory Viruses Editor's note, Oct. 11, 2021: Since this story was first published, COVID-19 arose and mask-wearing became an important public health tool. So we asked Pergam to revisit his earlier comments on masks in this story. Here's what he had to say: The discussion around masks has changed dramatically over the last year and a half. Previously, if you had asked me, I would have been less pro-mask during respiratory virus season, but as the COVID-19 pandemic has spread, there are more data that masks provide additional protection. They aren't perfect and the protection varies by the quality of the mask (N-95/KN-95s are better than single-ply cloth masks) and how well the cover the face (they need to cover the nose and mouth) but, regardless, I think there is a role for protecting patients when in large gatherings or out in public spaces. What will be interesting will be to see if what has happened during the pandemic will continue for years to come. However, for cancer patients, I see potential advantages and few, if any, downsides to their use. 11. Why do people often get a cold after flying on a plane? When you’re sitting in close proximity to others for 12 hours, you’re more likely to be exposed to respiratory droplets. It’s really limited to the seats around you, not the whole plane. I sat next to somebody with a cold, and I was as careful as I could be — washing my hands, using hand sanitizer. After a 10-hour flight I was sure I was going get a cold — and I did. 12. In what way is having kids like flying on a plane? The majority of people get colds and flu from being in close proximity to someone with an active cold, who’s sneezing and coughing. That’s why with young kids in a family, the cold goes through the whole family. Also, kids are viral factories: They often have viral loads that are higher than adults. They often don’t cover their nose and mouth, don’t have good hand hygiene, they hang out together at daycare and school. They’re the starting and ending place for lots of respiratory viruses during the cold season. We see the season happening in kids first. 13. How can you tell if you’ve got a cold or the flu? Runny nose, sore throat, fever, sneezing, cough and muscle pain are common symptoms seen in a whole host of viral infections. But influenza is different from a bad cold. It often includes a fever and a feeling of malaise or muscle pains. You feel really wiped out. If you are concerned, see your doctor for a quick test to see if you have flu or if it’s beneficial to get treated. Certainly, if you are a cancer patient, see your doctor even if you have minor symptoms. 14. What about the ‘stomach flu?’ That’s not influenza. Really young kids can get nausea and vomiting with influenza, but there are always respiratory symptoms. When you hear “stomach flu,” nausea and vomiting, think Norovirus. It is very contagious so oftentimes it will run through the whole family. 15. Any idea what kind of flu season it’s going to be this year? Sporadic cases have been seen, but it is not really spreading dramatically in the U.S. yet. It usually starts on the East Coast and moves West. Getting your flu shot now is ideal because you need two weeks to develop a full immune response. 16. So it’s a good idea to get a flu vaccine? It is the best way to protect yourself from getting the flu. It isn’t perfect but it can often cut your chances of getting influenza by about 50 percent (depending on the season). Unfortunately, we don’t have vaccines for other respiratory viruses. But I get my flu shot every year, as do all the physicians at the Seattle Cancer Care Alliance — we all know how important getting the vaccine is to protecting our families, our friends and our patients. SCCA and Fred Hutch provide free flu vaccine for our staff. In addition, we provide vaccine for patients and give it free to family members and caregivers when they come with patients to the clinic. 17. What about the high-dose vaccine? A high-dose flu vaccine has been shown in studies to provide better protection for people 65 years and older. I recommended it to my own parents — who both get vaccinated. The one down side is it only covers three strains of influenza while the normal vaccine covers four. Future studies should help us better understand whether high-dose vaccine is beneficial for cancer patients. 18. Why did the CDC stop recommending flu mist for children? The flu mist, or live-attenuated flu vaccine, is a weakened form of the influenza virus that can be given through the nose. It was thought to work well in kids, but recent data suggests that it may not provide enough immune response to some strains of influenza. The CDC does not recommend it as an option for vaccination this year. The only option is the flu shot. 19. Can you get the flu from the flu vaccine? Absolutely not. The vaccine has components of the inactivated virus, but it’s not the virus. Minor side effects can be a little aching or arm swelling, but it lasts a day or two at most. As one of the most utilized vaccines in the world, it has one of best safety profiles of anything we do in healthcare. 20. What about claims that vaccines are linked to autism? This has been well studied and there are no links. We need to move away from blaming vaccines for a very serious disorder when science has, again and again, shown this not to be the case. Unfortunately, many still believe this discredited link. As for Guillain-Barre syndrome (a rare neurologic illness), you are more likely to get it if you get the flu than if you get the vaccine. Vaccines are well studied and very safe. I get mine every year and so does everyone in my family. 21. Does drinking orange juice or taking vitamin C help prevent colds and flu? What about Airborne products or zinc? There’s not great data. Is it vitamin C that provides the benefit or drinking lot of orange juice? Probably the liquids. Eating healthy foods and getting lots of rest are important, however. 22. Is there any treatment for a cold or flu? If you have influenza, there’s Tamiflu, or oseltamivir [prescription antiretroviral drugs]. We don’t recommend them for everyone but we do suggest them for people with chronic health conditions, cancer or for a transplant patient at risk for complications. I prefer that you never need medications — get the vaccine instead. For most other respiratory viruses, there are no treatments, so prevention and limiting transmission are key. 23. Is there anything you can do to treat a cold? The best things you can do are rest and get adequate fluids. Take it easy, don’t exert yourself. Cover your coughs and sneezing. And stay home so you limit exposing others to the infection. 24. What about chicken soup? If nothing else, it provides a variety of nutritional benefits, a fair amount of liquids, and it can be very soothing to take something warm. I know I love it when I feel sick — along with ginger ale. It reminds me of when I was a kid. There are no downsides to it. Have you been hit by a cold or flu this season? Tell us about it on Facebook. |
Are you still contagious if you have a cough
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