Component 1A: Surface Sampling

People infected with COVID-19 expel the virus in small droplets through coughing, sneezing, talking, and breathing, particularly early in their infection.

Why sample surfaces

Infected people can spread these tiny droplets containing the virus even if they have no symptoms; in fact, asymptomatic transmission is thought to be a major driver of the COVID pandemic. After floating around in the air for a while, these aerosolized droplets eventually settle on surfaces in the room where they are expelled, and on those surfaces traces of COVID-19 can be detected. Surface sampling is an easy and effective strategy to identify whether persons in a given classroom or indoor work space may be infected with COVID-19. 

Identifying potential infections

When a potential infection has been identified via environmental monitoring, schools should ensure extra precautions are taken until the positive person is diagnosed and isolated (Component 3B). This should include ensuring high levels of ventilation via HEPA filters, opening doors and windows, and engaging in double masking and/or utilizing higher quality and better fitting face masks such as N95s or certified KN95s. Schools may also choose to use outdoor teaching facilities at this time, if this is a viable option.

Transparent community engagement

We strongly encourage the broadest degree of transparency in this step.  This is important so that administrators can take appropriate actions and so that families know they should get tested. Notifying the broader school community – family and household members of students, teachers, and staff – and advising anyone with concerns or potential exposures to seek out COVID-19 diagnostic testing can help both quickly identify the source of a case on campus, and potentially prevent broader spread within the general community. 

How does it work?

At the end of each day of instruction, a staff member (teacher, custodian, office personnel, administrator – different SASEA pilot sites used each of these options) dips a swab in a barcoded vial with a detergent solution in it, and rubs the swab in a single location near the middle of the room, usually the floor. The swab is placed in the vial, the vial is placed in a small baggie and labeled with the date and room number. This process takes less than one minute. Detailed directions for surface swabbing are found here and a brief training video is found here. 

The sample is deposited in a central collection bin, usually in the office. That afternoon/evening, a courier service logs the samples and transports them to a partner lab that conducts PCR analysis on the samples to look for traces of the COVID virus. The lab notifies the site or SASEA coordinator of the results for each swab/room. A positive surface swab suggests that there is a COVID-infected person in the room where the swabbing was done.

Requirements

  1. Designated staff members to swab each day
  2. Materials: swabs, vials, baggies, gloves, collection bin
  3. Courier service to log samples and deliver them to a lab
  4. Lab to analyze samples and report results, ideally within 24 hours of receiving the samples
Sampling kit supplies: surface sample selection tube, sterile flocculated swabs, suspension buffer, and resealable bags.

Limitations

  • While a major advantage of surface swabbing is that it is room specific, that advantage evaporates if many students enter the room during the day, such as a cafeteria or a classroom in a typical secondary school schedule. 
  • In a room with good ventilation, such as many open windows and/or a highly efficient air exchange system (all of which are excellent COVID safety strategies), COVID particles expelled by an infected person may not settle on the surface that is tested.
  • If an infected person is wearing a well-fitting, highly effective mask at all times, then COVID aerosols are less likely to escape and settle onto surfaces for detection where they could be detected with a surface swab. However, masking at this level of efficacy also significantly reduces the risk of secondary spread in a classroom.

Costs

  • Materials (one swab/vial/baggie/pair of gloves per classroom per day)
  • Courier service
  • Lab analysis (similar to diagnostic test cost)
  • Coordinator

A classroom full of kids where there’s no way to social distance was a little bit daunting. I was a little nervous about doing it without dividers…and so when the results started coming in I just thought ok so there’s no [positive] swab this week for my floor …. that makes me feel comfortable. That makes me feel a lot better about it. And the fact you have it so quickly, that if there were cases it would be dealt with immediately …it just gives me security. It makes me feel safer at school.

Classroom teacher

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