Why talk about the most common infections in schools and how to prevent them? Because, in school and college settings, infections can spread fast. Close quarters, shared spaces, and group activities make classrooms fertile ground for infections to spread. The most common being respiratory and gastrointestinal (GI) infections.
It started with a single student sneezing into her sleeve during second period. By the end of the week, half the class was out sick. Sound familiar? When the sniffles start in one classroom, they often ripple through an entire school. Whether it’s a coughing preschooler, a vomiting fifth-grader, or a college student with pink eye, infectious illnesses are a regular part of educational life and crowded places.
But which ones strike hardest and when? Understanding what’s circulating, and who’s most vulnerable, is key to prevention and response.
This guide explores the most common infections, grouped by respiratory and gastrointestinal (GI), so you can recognize and prevent them more effectively.
Respiratory Infections: Meet the Usual Suspects
1. Influenza (Flu)
Flu is a respiratory illness that is common in all age groups. In K12 setting there is a notable high absenteeism in middle and high school.
Symptoms: Seasonal flu causes fever, fatigue, cough, and body aches.
Spread/Transmission: Flu is highly contagious. It spreads through coughs, contaminated surfaces/dirty hands, shared water bottles, locker rooms, to mention some common modes of transmission. This virus can commonly be found on palms of hands
Season: Flu spikes in winter.
Impact: Flu can sideline entire classrooms or teams causing wide disruption. Flu outbreaks often start in classrooms and make their way through sports teams, school buses, and families.
2. Respiratory Syncytial Virus (RSV)
RSV is most common in preschool and early elementary (ages 0–6).
Symptoms: Teachers of pre-K and kindergarten may see waves of coughing, wheezing, and fever. RSV can lead to serious illness in younger children that can even lead to hospitalizations.
Spread: RSV spreads through coughing, sneezing, or contaminated surfaces.
Season: RSV infections occur most commonly during fall and winter months. Indeed, RSV is a major reason for winter absences, i.e. absenteeism in young children.
3. The Common Cold (Rhinovirus)
The common cold is the most common respiratory infection in K–8 students.
This is a perennial visitor that thrives in elementary schools, because that is where kids are still learning basic hand hygiene. As a matter of fact, common cold is nearly constant in early childhood classrooms.
Symptoms: Symptoms are usually mild and include a runny nose, sore throat, sneezing, and mild fever.
Spread: Though usually mild, the common cold spreads easily through hands, sneezing, coughing, doorknobs or shared toys and school supplies. This virus can commonly be found on palms of hands.
Note: It is interesting to note that kids may have 6–10 colds per year (even with normal immune system!)
4. Strep Throat (Group A Streptococcus)
Strep Throat is most common in elementary and middle school.
Symptoms: Strep Throat is known for sudden onset sore throat and fever.
Spread: Strep throat spreads rapidly through close contact. It spread easily during lunch or recess.
Impact: Without treatment, strep throat can lead to complications, so awareness is key.
5. Mycoplasma pneumoniae (“Walking pneumonia”)
Mycoplasma pneumoniae is most common in teens and young adults.
Symptoms: This is a sneakier illness, that causes fatigue and persistent dry cough. It is common in high school and college environments where students may delay seeking care.
Spread: Mycoplasma spreads through shared air in classrooms and on sports teams. Notable trait: it often goes undiagnosed for days.
7. Adenoviruses
Adenoviruses are group of about 50 types of viruses that can infect humans. They are most common in children younger than 5 years old but can infect older children and college students as well. In 2018, Adenovirus Type 7 killed a college student at University of Maryland and 11 deaths in children at the Wanaque Center for Nursing and Rehabilitation in Haskell, New Jersey.
Symptoms: Most adenovirus infections are mild and include cold-like symptoms with cough, fever, runny nose, sore throat. In addition, it can mimic flu.Furthermore, it can cause pink eye and ear infections.
Spread: Adenovirus spreads easily in babies and daycare centers, especially through shared toys and objects. In addition, lack of proper handwashing is a contributing factor. In adults, spread can occur in crowded environments like dorms, or hospitals and nursing homes. If someone has weakened immune system, they are more likely to get seriously ill from adenovirus infection (causing pneumonia).
Adenovirus infections occur throughout the year, but they tend to peak in the winter and early spring.
GI Infections: The Other Side of the Hallway
1. Norovirus
Norovirus affects all age groups, including rapid outbreaks in cafeterias and dorms.
Symptoms: This notorious “stomach bug” causes sudden onset of vomiting, stomach cramps and diarrhea. Norovirus is one of GI viruses. Other GI viruses include: rotavirus, astrovirus, adenovirus, sapovirus to mention few.
Spread: Norovirus is highly contagious. It is known ans the “Ferrari of Viruses” because of hos fast and easy it spreads. It is often transmitted by touching contaminated surfaces (including those that were NOT cleaned properly), eating shared food, and poor hand hygiene. In college, dorm kitchens and shared bathrooms make outbreaks nearly inevitable. his virus can commonly be found on palms of hands.
Impact: Norovirus can sweep through a school or college in days if not contained. It is spreading very fast. One sick child can cause a whole classroom to fall ill.
2. Rotavirus
Rotavirus is most common in preschool and early elementary students, especially where handwashing is inconsistent.
Symptoms include fever, vomiting and watery diarrhea. Symptoms usually start 2 days after exposure to the virus with fever and vomiting, followed by 3-7 days of watery diarrhea.
Spread: fecal-oral route (which means from poop to mouth); from toys, bathroom handles, or food.
Note: Vaccines help, but outbreaks still occur where handwashing is inconsistent – emphasizing the importance of good handwashing in prevention.
3. Salmonella
Salmonella is the most common form of bacterial food poisoning in the U.S.
These diarrheal infections are common in middle school to college and beyond.
Symptoms include diarrhea (sometimes bloody), fever and severe stomach cramps.
Spread: This is a foodborne illness (which means it spreads through contaminated food). An infection usually happens when students: 1. Touch contaminated surface and then put their dirty fingers in their own mouth; 2. Eat contaminated food, water, meats, eggs, unpasteurized milk etc. 3. Have contact with infected fecal material transferred to food area through unwashed hands. In schools, these foodborne bacteria can strike after a contaminated school lunch or potluck school events.
Scenario story: “The Macaroni Mishap”
At a high school potluck, one student brought homemade macaroni salad but left it unrefrigerated for hours. Two days later, over a dozen students were home sick with diarrhea and cramps. The culprit? Salmonella.
The school acted quickly: suspending food-sharing events, deep-cleaning surfaces, and launching a food safety workshop. In addition, students and staff with Salmonella infection were excluded until diarrhea was gone. It became a turning point in how students thought about hand hygiene for infection prevention and leftovers.
4. E. coli
E coli is short for Escherichia coli, a group of bacteria that normally live in the intestines. Yes, E.coli normally cohabitate in humans! While most E.coli are harmless, some can make people sick from food poisoning. E. coli 0157:H7 is the most common culprit.
Symptoms: most common symptoms are diarrhea (sometimes bloody); abdominal cramps, and vomiting.
Spread: E coli can spread by eating contaminated food (especially undercooked beef, raw milk, contaminated fruits and vegetables). In addition, the common mode of transmission is direct person to person transmission via contaminated (dirty) hands. This bug can be found on fingertips and under the nails.
Interesting fact: about 1/3 of infected children can carry (and transmit) the bacteria for 3 weeks.
4. Giardia
Giardia is most common in: elementary school and college students (especially post-travel)
Symptoms: This waterborne parasite causes bloating, foul-smelling greasy and long-lasting diarrhea, and fatigue. These symptoms can last for weeks.
Spread: Giardia spreads through contaminated, dirty water or poor hand hygiene, especially after international travel or camping trips.
5. Clostridium difficile (C. diff)
C. Diff is rare but possible in students who recently took antibiotics. This infection is more present in vulnerable populations, adults, or healthcare training programs.
Symptoms: Watery diarrhea, abdominal pain
Though rare in the general student population, C. diff is worth watching for in vulnerable groups or students training in clinical settings.
Spread: Fecal contamination in shared bathrooms or medical training sites.
Other infections not mentioned here include pink eye (conjunctivitis), hand-foot-and-mouth-disease (HFMD), Covid19, parainfluenza (croup) head lice, chickenpox, meningitis, mononucleosis or “kissing disease”.
Prevention: Where Stories Turn Into Success
When Ms. Lopez, a middle school principal, noticed a spike in GI absences after a school dance, her team sprang into action: intensified cleaning protocols, handwashing campaigns, and communication with parents. The outbreak was contained in 72 hours.
Her success was not luck. Her success was preparedness, based on understanding the infections that schools are most likely to face.
Best Practices for School & College Health
Here are some suggestions for the best practice for school and college health.
First of all, keep emphasizing and reinforcing proper hand hygiene, especially before meals and after bathroom use. Second, provide good ventilation particularly in older buildings and crowded rooms. To avoid students and staff attending school while contagious, it is important to have flexible sick-day policy. Lastly, communication is important, especially to update families during outbreaks.
Final Words: Learning to Stay Well
From preschool sniffles to college GI bugs, infections are an expected part of life in educational settings. But with the right mix of knowledge, communication, and basic hygiene habits, schools and colleges can stop outbreaks before they start— and create safer, healthier places to learn.
By matching prevention to age and environment, schools can turn vulnerable moments into opportunities to teach health, hygiene, and resilience. These are the skills that last long after the school bell rings. These are skills for life.
Dr. Jasminka Vukanovic-Criley MD, FACP, FHM is a multiple award-winning physician, internist, hospitalist, healthcare & education innovator & Associate Clinical Professor of Medicine at UCLA. She is a career mentor & advisor to numerous undergraduate, graduate & postgraduate students & faculty. As a researcher, Dr. Criley received awards from the National Institutes of Health & the U.S. Department of Education Her work focuses on creating research-driven #edtech games & digital media to improve health, civics, science education & promote healthy habits. Dr Criley is also a sought-after speaker & a founding Board member of Physician’s Weekly. She can be reached on X at @criley_md and at www.linkedin.com/in/jasminka-criley-md