Study Reveals Impact of Air Filters on Respiratory Virus Spread in Schools

Respiratory infections like SARS-CoV-2 and influenza are hard to control. These viruses mainly spread when people release tiny droplets from their mouths and noses. Recently, researchers have been paying more attention to very small particles called aerosols, which carry a lot of viruses during activities like talking and Coughing. Unlike larger droplets that fall to the ground quickly, aerosols can stay in the air for hours and travel far distances.

To reduce the spread of these infections, improving ventilation in indoor spaces is very important. Good ventilation helps lower the chances of virus transmission, especially in places like schools where students spend most of their time indoors. Portable Air Filters might also help, but it is not clear how effective they are in stopping the spread of Respiratory Viruses. Some studies have shown that schools using various ventilation systems, including air filters, report fewer cases of SARS-CoV-2.

Although air filters can lower particle levels in the air, it does not always mean they reduce the amount of virus that can infect people. Some studies show that air filters do a good job in hospital settings, but it is uncertain if they can do the same in classrooms. Most studies assume that if a virus is found in the air, it is infectious. However, recent findings suggest that viruses can lose their ability to infect over time.

We conducted a study to look at how respiratory viruses spread in a school setting without a pandemic going on. We also wanted to see how air filters might help. Our study took place in two secondary school classes in Switzerland during the winter of 2022 to 2023. We gathered a variety of data for seven weeks, which included measuring Air Quality, counting student absences related to illness, recording coughing sounds, and checking for viruses in both air and Saliva Samples.

#Study Details

#Setting and Design

Our research was conducted in two classrooms at a secondary school in Switzerland. We collected data from January 16 to March 11, 2023. Each classroom had one air filter placed in the front and another in the back. The classrooms did not have any active heating, ventilation, or air conditioning system, but teachers could open windows to let in fresh air.

#Study Intervention

We used a special study design where air filters were turned on and off at different times in each classroom to see how they affected air quality and virus spread. The air filters we used were portable and designed to remove small particles from the air. In tests of these filters in empty rooms, we found that they worked effectively but not quite as well as advertised.

#Data Collection

We gathered various types of data during the study.

#Environmental Data

We measured air quality continuously to track levels of carbon dioxide (CO2), number of small particles in the air, and particle mass concentrations.

#Epidemiological Data

At the beginning of the study, we collected data on the age and vaccination status of the students. Each day, we kept track of students who were absent due to illness and recorded their symptoms.

#Audio Recordings and Cough Detection

We used audio recorders to capture sounds in the classroom over time. An artificial intelligence algorithm helped identify how many times students coughed.

#Molecular Data Analyses

Students participated in regular saliva testing to check for respiratory viruses. We also collected samples of airborne viruses using a special device that sucked air into a collector during class time. Samples from the air filters were collected after each phase of using the air cleaners.

#Results

#Respiratory Virus Detection

Through our testing, we found a variety of respiratory viruses in students' saliva, including adenovirus, influenza B, and rhinovirus. Only a few cases of SARS-CoV-2 were detected. Most respiratory viruses were carried in tiny particles, which makes it hard to see how they spread in a classroom setting.

#Air Quality Measurements

We noted that the number of small particles in the air was much lower when air filters were used. Our analysis showed a significant drop in particle levels, indicating that air filters were effective in improving air quality in the classrooms.

#Illness Reports

We saw fewer cases of respiratory illness among students when air filters were in use compared to when they weren’t. The overall risk of getting infected seemed lower with the air filters. The data suggested a clear trend that using air filters helps reduce the spread of respiratory infections.

#Coughing Observations

Coughing, which is linked to the spread of respiratory viruses, was also less frequent when the air filters were on. Our findings indicated that air cleaners might help reduce coughing, which is a sign of respiratory illness.

#Saliva Sample Analysis

In total, we tested many saliva samples for viruses. The most common viruses detected were adenovirus and influenza B. The presence of the viruses varied by class, suggesting some classes had more infections than others.

#Discussion

#Implications on Virus Transmission

Our study shows that many respiratory viruses were present in students but rarely in the air. This indicates that while respiratory viruses can be detected, they might require close contact to spread effectively. Most infections may have come from outside the classroom rather than airborne transmission within it.

#Limitations

Our study does have some limitations. We can measure exposure to viruses through air samples, but we cannot say for sure how they transmit or prove that they spread from the air to people or vice versa. Also, some student absences may not have been accurately reported, and we could only make educated guesses about how long students were infected.

#Conclusion

A variety of respiratory viruses were detected among students, but SARS-CoV-2 was much less common. The low presence of respiratory viruses in the air suggests that close contact is often necessary for them to spread. Air filters can help reduce the risk of respiratory infections, but their effect at the individual level may not be very large. However, at a larger scale, the use of air filters could result in fewer illnesses and absences among students. Future research should look further into how effective air filters can be in places where large groups gather.