Introduction

Respiratory syncytial virus (RSV) is a common respiratory viral infection that causes mild cold-like symptoms in the winter. RSV can be classified into two strain types:¹

• RSV-A 
• RSV-B

Both strains can be differentiated depending on the proteins present on their surfaces. RSV-A is more prevalent than RSV-B, but there is no clinical difference between the two strains of viruses.¹

RSV is a global virus that infects the lower respiratory tract and affects all age groups. Symptoms of RSV usually show 4-6 days after infection and appear in stages. They include:

• Coughing and wheezing
• Sneezing and a runny nose
• High fever
• Decrease in appetite

Symptoms can vary depending on the age of the patient. Adults and older adults usually have mild symptoms, whilst infants and young children can have more severe symptoms. Most patients with RSV recover from the infection within a week without any medical treatment required, but there are some risk groups where RSV may cause complications. High-risk groups include:

• Premature infants
• Immunocompromised individuals, such as cancer patients who are taking chemotherapy drugs or HIV patients
• Individuals with chronic medical conditions
• Older individuals over 75 years old

In infants and younger children, initial RSV infection can cause severe bronchiolitis, which can be fatal. RSV also poses a threat to older adults, within whom there is more hospitalisation caused by RSV in patients aged over 65 years of age.

Transmission of RSV is caused by the spread of viral droplets that are released when an infected patient coughs or sneezes. The viral particle can then enter through the nose, the eyes or the mouth. It can also be spread through contact with infected surfaces, such as door handles, staircases, doors, and even clothes. RSV can therefore spread in schools and childcare centres like wildfire, infecting most school pupils due to close contact in high-density environments. This article will discuss the environmental factors (indoor, outdoor, social and behavioural) that contribute to RSV outbreaks in schools. Then, it will provide strategies to prevent them.

Indoor environmental factors

As mentioned above, RSV is spread by viral droplets released when an infected patient coughs or sneezes, called droplet spray transmission, and by touching infected surfaces. This is called contact transmission.² 

Temperature and humidity

Temperature and humidity are known to have an impact on the transmission of RSV in school outbreaks.² RSV peak outbreaks occur during winter because pupils spend more time indoors and in close contact with each other. This is the perfect situation for RSV to spread from one person to another. Moreover, during the colder months, the virus is more stable and can last longer on surfaces, increasing transmission. 

Humidity can impact the transmission of viral droplets in the air by affecting how stable the droplet is and its size.² Humidity is an important factor influencing how long the viral droplets stay in the air, affecting transmission rates. At lower humidity, viral transmission is more efficient, as the viral droplets will remain in the air longer, meaning there will be a higher chance of transmission.² During winter, schools are heated, creating a low-humidity environment, leading to more transmission of RSV, especially in a crowded place like a school.

Low temperature leads to changes in the immune system, such as reducing and impairing the mucosal clearances in the respiratory tract, which can lead to someone being more susceptible to RSV infection.² During winter, there is also seasonal nutritional deficiency of vitamin D when there is less sun, and this deficiency can also impair the immune system.

Air quality

The air quality of a classroom in terms of airflow and ventilation is an important factor that can impact an RSV outbreak. 

There is a lower rate of transmission of viral infection when there is good increased ventilation as the air is mixed with fresh air from outside, which removes the viral droplets. As there is a lower concentration of RSV viral droplets in the air, there will be less RSV infection, preventing RSV outbreaks. Inadequate and outdated ventilation systems can increase RSV outbreaks due to insufficient air exchange and poor airflow.² 

Indoor air pollution, such as dust, mould, and smoke, can contribute to respiratory infections. Studies have shown a strong correlation between increased air pollutants and higher viral infection rates. Air pollutants impact students' respiratory health as they can induce the release of pro-inflammatory cytokines by the immune system. An increase in these cytokines is associated with higher viral infectivity as the virus is able to adhere to the host cells and begin its viral replication.³ 

Surface contamination

As discussed earlier, RSV can be spread when an infected individual touches surfaces after coughing and sneezing. The frequency and methods of cleaning and disinfecting high-touch surfaces, like doorknobs and staircase handles, is an important factor that explains why RSV outbreaks frequently occur in schools. If the contaminated surfaces are not cleaned frequently and well, they will allow the virus to spread easily from an infected student to a non-infected one. Children are often in confined rooms, where high-touch surfaces and materials, such as paper or pens, are shared, allowing RSV to spread easily. 

Outdoor environmental factors

Seasonal changes

Weather patterns are a known environmental factor that can influence RSV outbreaks in schools.² The highest peak during the RSV season is December. During the cold and rainy weather, most students are kept in crowded rooms indoors and this proximity is responsible for increased RSV transmission. Crowded areas facilitate RSV to spread through viral droplets or by touching surfaces. In this season, the school heating is turned on and this causes low humidity in the rooms, which also increases the transmission. 

Environmental pollution

Outdoor air pollution is another factor that can impact respiratory health and exacerbate RSV and other respiratory infection outbreaks. Air pollutants include:⁴

• Particulate matter
• Ozone
• Nitrogen oxides
• Sulphur oxides
• Carbon monoxide

Higher exposure to air pollutants is associated with adverse health problems and can impact the respiratory system by:⁴

• Causing a deficit in lung function and growth
• Causing long-term respiratory damage
• Causing chronic respiratory diseases, such as asthma

Pollutants can impair the immune system and its response to a viral infection, allowing the virus to evade the immune system. The virus then reproduces without an immune response and can spread to other pupils in a school. 

Social and behavioural factors

Social and behavioural practices are other factors that can contribute to RSV outbreaks in schools. 

Hygiene practices

Washing your hands properly with soap and water can dramatically reduce the spread of RSV in schools. Poor school policies where hygiene education is neglected will mean there will be more RSV outbreaks. 

Covering one's mouth when coughing and sneezing can also reduce RSV outbreaks, but the importance of teaching and enforcing this practice is not done in schools. Neglecting teaching respiratory hygiene is a contributory factor to the outbreak of RSV in schools. 

Population density

Classrooms in schools are crowded places with many students in one room and this will allow for RSV to spread from one person to another with ease, either by droplet inhalation or by touching contaminated surfaces. Places like assemblies, sports clubs, and other community clubs and group activities also contribute to more RSV transmission. The larger the group, the higher the infection rate, as more people are interacting and infecting each other.

Mitigation strategies

There are a number of possible steps to take to mitigate the impact of RSV in schools. Here are some steps to prevent RSV outbreaks in schools.

Air quality must be improved to bring in fresh clean air inside. This can be done by maintaining the ventilation system and considering upgrading the air purification systems. It is important to change the filter in the system regularly and to clear the system properly

Controlling the temperature and humidity levels. Keeping the rooms warm and at a high humidity will prevent RSV outbreaks. It is recommended to use humidifiers in schools to prevent RSV outbreaks.

Implementing hygiene practices. It is important to understand and implement hygiene practices such as washing hands and covering faces when coughing and sneezing in both students and staff to prevent the spread of RSV in school. In addition, high-touch surfaces must be regularly cleaned with strong disinfectants to reduce RSV transmission. 

Summary

Respiratory syncytial virus (RSV) is a common respiratory viral infection that causes mild cold-like symptoms in winter. Transmission of RSV is caused by the spread of viral droplets that are released when an infected patient coughs or sneezes. The virus can also be spread through contact with infected surfaces. RSV can therefore spread in schools and childcare centres, infecting most school pupils due to close contact among them in a high-density environment. Environmental factors such as temperature, humidity, air quality, surface contamination, seasonal changes, and social behaviours can contribute to RSV outbreaks in schools. By choosing strategies that can mitigate these factors, the outbreaks of RSV in schools can be reduced.