You Think It’s Funny, but It’s Snot: Infection Prevention in Schools

As the autumn days grow colder, many families gather indoors to share meals, exchange hugs and kisses, and bask in the indoor warmth of the cooler season. These cherished traditions, however, also create ideal conditions for the spread of respiratory and gastrointestinal illnesses.

Then comes the winter break. When schools reopen after break, students and staff may return not only with stories from the holidays but also with viruses in tow. Protecting school environments from illness is no simple task—it’s a complex challenge that demands a science-based, proactive approach to indoor air quality, hygiene, and public health practices.

On May 17, 2024, the CDC released consolidated, evidence-based guidance for preventing the spread of infections in K-12 schools.¹ The CDC guidance includes everyday actions that schools can take to prevent and control the spread of respiratory and stomach viruses, such as influenza and norovirus, and bacterial illness, like strep throat.

The goal of the CDC guidance is to maximize school attendance while minimizing the spread of infectious diseases because being in school offers critical benefits, including consistent learning, social interaction, and emotional development.

The CDC strategies are based on research and expertise gained from decades of work to prevent disease transmission in school settings, as well as lessons learned from the COVID-19 pandemic. The Department of Education’s infection control guidelines also align with CDC recommendations. They both outline practices that schools should follow to prevent the spread of infectious diseases among students and staff, including regular hand washing, proper cough etiquette, cleaning and disinfecting surfaces, and procedures for managing suspected cases of communicable diseases within the school setting.¹

How Microbes Spread in Schools

Many factors can increase the risk of transmission of communicable diseases in schools. Factors such as close contact with others, sharing of objects, inadequate personal hygiene supplies or practices, and students or staff who attend school while sick.

The types of infectious diseases commonly found in schools are²:

• The common cold: Spread by cough, sneeze, and contact with objects that microbes have landed on.
• Diarrheal illnesses: Spread by fecal-oral contact, consuming food or drinks contaminated with feces, touching diarrhea or vomit, or breathing air from the same room in which someone has just vomited.
• Mononucleosis: Spread by mouth-to-mouth contact, sharing drinks, drinking cups, and other objects.
• Strep throat: Spread by cough, sneeze, and contact with objects microbes have landed on.
• Influenza: Spread by cough, sneeze, and contact with objects on which microbes have landed.

Microbes depend on people, animals, the environment, and/or shared objects to move about. The spread of microorganisms can be prevented by adhering to evidence-based practices and having plans in place that can help reduce illness and illness-related absenteeism by preventing the spread of common infections.

The mode of transmission is particularly important because it describes how microorganisms are transmitted from one person or place to another. (Figure 1)

Close contact between students is a significant factor in the spread of microbes across the school environment. The main modes of organism transmission in schools are contact transmission—both direct and indirect, eg, shaking/holding hands, coughing/sneezing, vomiting; and indirect (fomites)—touching contaminated surfaces or people.

Fomites are inanimate objects, environmental surfaces, or food and drink that can carry and spread disease and infectious agents. Surfaces that multiple people frequently touch pose the most significant risk, including door handles, tables, desks, restroom surfaces, eating and drinking utensils, writing utensils, shared electronic devices, and toys.³ Fomite transmission is usually associated with the transmission of respiratory and gastrointestinal disease.

School-age children who require diaper changes, assistance with toileting, or those who don’t wash their hands adequately after toileting or cleaning up after a child has had a soiling event can also spread infection via the fecal–oral route, through both direct and indirect contact. Poop is considered direct contact when someone comes into direct contact with feces. Indirect contact occurs when someone ingests contaminated food or water or touches contaminated objects or surfaces. Feces can spread organisms like Shigella, Norovirus, and Salmonella, all of which cause diarrhea. Feces can also spread respiratory infections, such as adenovirus and hand, foot, and mouth disease. Contact with animal feces, like the classroom guinea pig, can also spread microorganisms if hands aren’t washed.

Some organisms can also be transmitted through blood. This type of transmission in school settings is rare. Always follow your facility’s plan for blood exposures. (Figure 2)

Layered Prevention Strategies: A Blueprint for Healthier Schools

Studies from the COVID-19 pandemic have shown that robust, layered infection prevention and control everyday actions can help schools operate to minimize the spread of infections, even during a pandemic. These everyday actions involve taking steps to improve air quality and enhance ventilation, including cleaning, sanitizing, and disinfecting, as well as practicing proper hand hygiene, respiratory hygiene/cough etiquette, and getting vaccinated.⁴

IPC in schools requires focus on each of these areas or “layers.” Think of each layer as a slice of Swiss cheese—each has holes (limitations), but when stacked together, the holes are covered by other layers. They block more pathways for infection. No single measure is foolproof, but combined, they contribute to reducing the risk of transmission.

This Swiss Cheese Model of defense helps reduce reliance on any single measure. It provides backup if one layer fails, and adapts to changing conditions (eg, during flu season or a new outbreak).² (Figure 3)

Example: Good ventilation reduces airborne virus particles; however, if someone sneezes on a desk, cleaning and proper hand hygiene are necessary to prevent the transmission of viruses to surfaces.

Here's a breakdown of how these layers work together and why they matter:

Cleaner Air and Better Ventilation

Microorganisms spread more readily between people indoors than outdoors. This is particularly concerning, given that humans spend the majority of their time indoors, where air quality is often poorer than it is outdoors. These factors have a significant impact on human health and well-being.

The primary indoor environment for most people is their home. For the average American adult, the workplace is the second most frequented indoor space. In contrast, for school-age children and teenagers, that space is typically the classroom.

Understanding how indoor environments impact health is crucial for enhancing public health outcomes, particularly in areas where people spend a significant portion of their day. The indoor environment in schools plays a critical role in the health and safety of students and staff.

Given how much time children spend inside school buildings, improving indoor air quality (IAQ) and ventilation is not just a health precaution—it’s a critical component of educational infrastructure. According to the Environmental Protection Agency (EPA), about 46% of all public schools suffer poor indoor environmental quality. And 50% of schools self-report unhealthy indoor air quality.⁵ These figures highlight a widespread issue that directly affects student health, concentration, and academic performance.

Ventilation reduces infection risk by diluting airborne contaminants (including viruses, bacteria, and allergens); removing stale air and replacing it with fresh outdoor air; and lowering the concentration of infectious aerosols, especially in crowded or poorly ventilated spaces.

Effective ventilation strategies to improve IAQ include⁴:

1. Natural ventilation: Open windows and doors when weather and safety allow. Hold some activities outdoors.
2. Mechanical ventilation: Ensure HVAC systems are functioning properly and meet the recommended air exchange rates; upgrade systems to enhance air exchange.
3. Portable air cleaners: Use HEPA-filtered units or air purifiers in classrooms and common areas.
4. CO₂ monitoring: High CO₂ levels can indicate poor ventilation—monitoring helps identify problem areas.

Improving IAQ isn't just about preventing illness—it's also about enhancing cognitive performance, as studies show that students perform better in well-ventilated classrooms. Improving IAQ also reduces absenteeism because fewer illnesses mean more consistent attendance. It can also help promote equity by targeting improvements that can help close health gaps in underserved communities that often have older school buildings with poor ventilation.

Cleaning, Sanitizing, and Disinfecting

Surfaces in schools—especially high-touch areas—can become reservoirs for infectious microorganisms. While surface transmission is less common than airborne transmission, it still plays a role in spreading illnesses such as norovirus, influenza, and the common cold. Maintaining clean surfaces helps reduce overall microbial load and supports a healthier environment.

Up to 15,000 microbes can be found on surfaces and objects in a typical school, according to ABC News.⁶ A study published in the Journal of School Nursing found that Influenza A virus was detected on up to 50% of student desktops; Norovirus was found on up to 22% of high-touch surfaces, such as stair handrails.⁷ Commonly contaminated surfaces in schools are desktops, faucet handles, paper towel dispensers, water fountain handles, pencil sharpeners, and keyboards.

Schools are high-risk for fomite transmission due to several factors:

1. Shared objects: Students frequently share supplies, desks, and equipment.
2. Close contact: Crowded classrooms increase the chance of cross-contamination.
3. Young age group: Children are less likely to follow hygiene protocols consistently.
4. Long exposure times: Students and staff spend 6–8 hours daily in the same indoor environment.

As in health care, the most important places to clean and disinfect are frequently touched surfaces, particularly during flu season or a virus outbreak. Ideally, frequently touched surfaces should be cleaned and disinfected on a daily basis. Common “high-touch or frequently touched surfaces” in schools are surfaces that are touched by many different hands.¹⁰

Common “frequently touched” surfaces in schools include computer equipment, musical instruments, doorknobs, elevator buttons, light switches, door push bars, handrails, water fountains, lockers, library tables, restrooms fixtures, and lounge and vending machines. These should be managed for infection control.¹⁰

There are also common “high-risk” areas in schools. These are areas that are more concerning for possible transmission of disease because there is an increased likelihood of skin-to-skin, object-to-mouth, or fecal-oral contact. Areas like the Athletic department, bathrooms, kitchens, lunchrooms, the nurses’ office, and childcare and preschool centers.¹⁰

Also considered “high-risk” are areas where food is prepared, sick or preschool children are cared for, or special events or incidents (such as blood or body-fluid spills) occur. Implementing surface cleaning strategies enhances safety, reducing the risk of infectious disease transmission.¹⁰

Layered infection prevention and control (IPC) measures for surface hygiene in schools include routine cleaning and disinfection of high-touch surfaces multiple times a day, the use of EPA-approved disinfectants, especially during flu season or outbreaks, education and training for custodial staff and teachers on proper cleaning protocols, and encouraging student involvement to promote hand hygiene before and after touching shared surfaces.

The impact of improved hygiene in classrooms cleaned daily with disinfecting wipes was evident, as students were 2.32 times less likely to report illness-related absenteeism. Targeted cleaning of desks and shared surfaces has been shown to reduce absenteeism by up to 50%.⁹

Hand Hygiene

Hands are one of the most common pathways for the transmission of germs. Whether it's touching contaminated surfaces, sharing supplies, or eating lunch, students and staff constantly use their hands, making hand hygiene a frontline defense against the spread of infectious diseases, such as colds, flu, norovirus, and COVID-19. Proper hand hygiene can reduce the incidence of respiratory illnesses by 21% and gastrointestinal illnesses by 31%.⁸ Schools that implement hand hygiene programs see lower absenteeism and fewer outbreaks.

Key steps to implement in hand hygiene programs in schools include¹:

1. Frequent handwashing: Encourage washing hands with soap and water for at least 20 seconds, especially before eating, after using the restroom, after coughing, sneezing, or blowing your nose, after touching shared objects, and when handling and caring for classroom pets.
2. Hand sanitizer station: Place alcohol-based hand sanitizers (containing at least 60% alcohol) in classrooms, entrances and exits, cafeterias, gymnasiums, and near high-touch surfaces.
3. Education and training: Teach proper handwashing techniques using posters, songs, or demonstrations. Reinforce with visual cues near sinks.
4. Modeling behavior: Encourage teachers and staff to model good hand hygiene to reinforce habits among students.
5. Accessibility: Ensure sinks are stocked with soap and paper towels, and that sanitizer dispensers are regularly refilled.

Respiratory Hygiene and Cough Etiquette

Respiratory droplets expelled during coughing, sneezing, or even talking can carry viruses like influenza, COVID-19, and respiratory syncytial virus. These droplets can land on surfaces or be inhaled by others, making respiratory hygiene a key layer in preventing the spread of infections, especially in crowded school environments. Promoting respiratory hygiene can significantly reduce the spread of respiratory viruses in schools. Combined with hand hygiene and surface cleaning, it helps create a culture of health and safety.

Key steps to implement Respiratory Hygiene and Cough Etiquette programs in schools include¹:

1. Cover coughs and sneezes: Teach students to use a tissue or their elbow, not their hands, to cover coughs and sneezes.
2. Provide supplies: Ensure classrooms and common areas have tissues, no-touch disposal bins, and hand sanitizer readily available.
3. Encourage mask use: During outbreaks or periods of high transmission, promote the use of well-fitting masks, especially for students or staff who are experiencing symptoms.
4. Educate and reinforce: Use posters, announcements, and classroom discussions to reinforce proper respiratory hygiene/cough etiquette.
5. Stay home when sick: Encourage students and staff to stay home when experiencing symptoms such as coughing, sneezing, or fever.

Vaccination

Vaccines are one of the most effective tools for preventing infectious diseases. Vaccines play a vital role in keeping children healthy and schools functioning smoothly. They not only protect the individual but also contribute to community immunity, reducing the overall spread of illness in schools. For diseases such as influenza, measles, and COVID-19, vaccination can significantly reduce the risk of outbreaks and minimize disruptions to learning.

Why Vaccines Matter for Kids in School Settings:

1. Provide protection against serious illnesses: Vaccines shield kids from diseases like measles, mumps, rubella, and whooping cough—illnesses that can cause severe complications or even be life-threatening.
2. Community immunity: When most students are vaccinated, it creates a protective barrier called herd immunity. This helps safeguard classmates who can’t be vaccinated due to medical conditions.
3. Fewer disruptions to learning: Vaccinated children are less likely to get sick, which means fewer absences and less chance of outbreaks that could shut down classrooms or entire schools.
4. Saves time and money preventing illness: Vaccination reduces healthcare costs and avoids missed workdays for parents and missed school days for kids.
5. Meets school requirements: Most schools require certain vaccinations for enrollment to ensure a safe learning environment for all students.
6. Builds lifelong health habits: teaching kids the value of vaccines helps instill responsibility for their own health and the well-being of others. Vaccination promotes equity, especially when access is facilitated through school-based programs.

Key steps to implement vaccination programs in schools include¹:

1. Promote routine childhood vaccinations: Ensure students are up to date on required immunizations (eg, MMR, DTaP, varicella). Provide reminders to families about state requirements and schedules.
2. Encourage COVID-19 and Influenza vaccinations: Recommend annual flu shots and COVID-19 vaccines for eligible students and staff, especially during peak seasons.
3. Host school-based clinics: Partner with local health departments or providers to offer onsite vaccination events. This increases access and convenience for families.
4. Educate families: Share accurate, science-based information about vaccine safety and effectiveness through newsletters, websites, and parent meetings.
5. Track and monitor: Maintain up-to-date immunization records and follow up with families whose children are missing required vaccines.
6. Address vaccine hesitancy: Provide clear and empathetic communication about vaccine benefits and risks. Offer Q&A sessions with health care professionals. Respect concerns while reinforcing the importance of protecting the school community.

Schools play a crucial role in preventing infectious diseases and ensuring the health and safety of students, staff, and the broader community. Developing a science-informed plan is the first step in playing this critical role. Everyday actions in the “layered” approach to IP in schools give the most protection against infectious illnesses. Remember the “cheese.”

References

1. Children and school preparedness. CDC. October 24, 2024. Accessed July 25, 2025. https://www.cdc.gov/children-and-school-preparedness/php/interventions/index.htm
2. Rose L, Westinghouse, C. Cleaning for healthier schools: infection control handbook 2010. Accessed July 25, 2025. https://portal.ct.gov/-/media/departments-and-agencies/dph/dph/environmental_health/eoha/pdf/cleaningforhealthierschoolsfinal2411pdf.pdf
3. Hendron, K. How germs are transmitted—and how to protect yourself. Updated June 15, 2025. Accessed July 25, 2025. https://www.verywellhealth.com/droplet-transmission-3956438#:~:text=Some%20germs%20can,may%20be%20contaminated
4. School preparedness. Everyday Actions for Schools to Prevent and Control the Spread of Infections. CDC. May 14, 2025. Accessed July 25. 2025. https://www.cdc.gov/children-and-school-preparedness/php/interventions/everyday-actions-for-schools.html
5. Romano, S. How school building conditions and indoor air quality impact education. January 3, 2022. Accessed July 25, 2025. https://iaq.works/indoor-air/how-school-building-conditions-and-indoor-air-quality-impacts-education/
6. ABC News. Schools can be a hotbed of bacteria. September 17, 2006. Accessed July 25, 2025. https://abcnews.go.com/GMA/OnCall/story?id=2455073&page=1
7. Bright KR, Boone SA, Gerba CP. Occurrence of bacteria and viruses on elementary classroom surfaces and the potential role of classroom hygiene in the spread of infectious diseases. J Sch Nurs. 2010 Feb;26(1):33-41. doi: 10.1177/1059840509354383. Epub 2009 Nov 10. PMID: 19903773. https://pubmed.ncbi.nlm.nih.gov/19903773/#:~:text=Abstract,infection%20and%20thus%20student%20absenteeism
8. Science brief: prevention and control of respiratory and gastrointestinal infections in kindergarten through grade 12 (K12) schools surface cleaning, summary of findings. CDC. Accessed July 25, 2025. https://www.cdc.gov/orr/school-preparedness/infection-prevention/docs/IPC-Science-Brief_508.pdf
9. Hernandez, M. Effects of classroom cleaning on student health: a longitudinal study. Journal of Exposure Science and Environmental Epidemiology, 2022. doi:10.1038/S41370-022-00427-8. https://www.academia.edu/127902113/
10. About hand hygiene in schools and early care and education settings. CDC. October 25, 2024. Accessed July 25, 2025. https://www.cdc.gov/clean-hands/prevention/about-hand-hygiene-in-schools-and-early-care-and-education-settings.html

More information:

A study published in the Journal of School Nursing found viral contamination on surfaces within school settings. Specifically, Influenza A virus was detected on up to 50% of student desktops, while Norovirus was found on up to 22% of high-touch surfaces such as stair handrails. This study suggests a link between classroom hygiene and student absenteeism due to illness. Source information

Title: Occurrence of Bacteria and Viruses on Elementary Classroom Fomites

Journal: Journal of School Nursing

Publication Details: While the exact year isn't explicitly stated in all snippet results, it can be found as 2010. It is worth noting that a study with similar findings was published on PubMed in 2010.

1 https://www.cdc.gov/children-and-school-preparedness/php/interventions/index.html

2 https://www.cdc.gov/orr/school-preparedness/infection-prevention/index.html