By Alison Kopelman, M.D., I.B.C.L.C., F.A.A.P., F.M.A.A.P

How long is my child contagious? This is a question frequently asked by doctors, families, and daycare providers alike. Here’s the answer – for most illnesses, we don’t know because there is no definitive example.

For example, Respiratory Syncytial Virus (RSV) is most often contagious for 3 – 8 days, starting one to two days before symptom onset. However, some individuals can spread RSV for up to four weeks! Hand, Foot, and Mouth (HFM) can be contagious for weeks – well after symptoms end.

The way I approach this issue is by gauging the severity/risk of illness and time of peak contagiousness and then providing guidelines based on these factors.

Most viral colds, while making children miserable, do not endanger health in a meaningful way. Viral colds consist of runny noses, mild coughs, and low-grade fevers. General advice is that children are okay to be out and about, but do try to limit/clean up snot as much as possible. I encourage families to view these mild colds as opportunities to build immune systems.

More serious illnesses such as strep throat, HFM, and influenza are MOST contagious in the days right before symptom onset until 24 hours after fevers end. For this reason, I tell families that children should stay home until 24 hours after fevers end to limit the spread of more serious illness. This is not a guarantee that all illness will be stopped – but the illness spread will be minimized.

Stomach bugs or “flus” that cause vomiting and diarrhea also do not have a definitive timeline for contagion. Most of the viruses that cause these illnesses can be contagious from symptom onset to two weeks after symptom resolution. The time of peak contagion, however, is from symptom onset until 24 – 48 hours after the last episode of vomiting or diarrhea.

When thinking about how contagious an individual is, it’s helpful to think about how viruses spread. There are three major modes for viral spread:

  • Hand contact – when one touches a contaminated object and then touches their own face. This is the most common way viruses are spread! (Think of all those adorable toddler hands touching EVERYTHING)!
  • Inhalation of viral droplets in the air (think uncovered coughing and sneezing).
  • Deposition of viral droplets directly onto one’s mucous membranes (think uncovered coughing and sneezing).

Good hygiene – consisting of frequent handwashing with soapy water, steering coughs away from others, and frequent nose wiping – is the best way to prevent the spread of illness. At home, or in daycares, wiping all surfaces frequently with a diluted bleach solution drastically cuts down on viral spread. If you want to prevent serious disease, stay home for 24 hours after your child’s fever, vomiting, or diarrhea has resolved and focus on continuing good hygiene.

Dr. Ali Kopelman is a local, board-certified Pediatrician and International Board Certified Lactation Counselor. She recently started a private practice, allowing her to practice relationship-based medicine. She has several interests, from Breastfeeding Medicine and support of new families to children with behavioral and mental health concerns of all ages.