Environmental Monitoring for Disease Surveillance is Here to Stay 

At the start of the COVID-19 pandemic tactics for measuring community levels of SARS-CoV2 were predominantly reliant on diagnostic testing and screening of the public. Fast forward two years, we’re still dealing with COVID, but our approach to disease surveillance has expanded beyond human testing, to air and wastewater.

^{This article is posted on our Science Snippets Blog} 

How to Track Down a Virus

The new normal has arrived. Armed with vaccines, antivirals and at-home tests, people are less inclined to visit the clinic for COVID testing. While this helps to reduce the burden on healthcare systems, it also means we are undercounting COVID cases. In fact, the Institute for Health Metrics and Evaluation estimates that we are missing as much as 93% of positive cases in the US due to home testing. 

This has created a shift towards capturing community-level snapshots of disease prevalence by sampling from indoor air and municipal wastewater treatment plants. These approaches take advantage of the natural shedding of pathogens in exhaled air or into wastewater systems. In both scenarios, specialized protocols and equipment are used to collect samples at regular intervals. Next, the sample is processed to isolate genetic material for molecular testing, such as RT-PCR, PCR and genome sequencing.

Benefits of Environmental Monitoring 

While clinical testing is still important, it is more costly and logistically complicated to implement in every setting. Environmental monitoring can complement public health efforts by addressing some of the gaps in testing and offering many benefits:

• Provides unbiased sampling; including asymptomatic cases
• Easier to implement and coordinate than mass testing
• Tracks the rise and fall of case numbers during an outbreak
• Enables early detection of pathogens and new variants
• Allows tailored response based on local case counts
   

  Application Note: Sampling of Human Pathogenic Viruses from Air by Gelatin Membrane Filters and Subsequent Detection by PCR Analysis

Air Monitoring for Airborne Pathogens

Some pathogens spread via tiny droplets, or aerosols, that enter the air when someone exhales, coughs, sneezes, talks or sings. Aerosols can linger for hours without proper ventilation, exposing others who share the air. Once it was established that SARS-CoV-2 spread via aerosol transmission, there was a greater focus on ventilation in classrooms, offices, hospitals, public transportation, and other crowded indoor spaces. 

Air monitoring tells us what microorganisms are in the air and serves as an early warning system of air quality. There are many factors to consider when designing an air sampling study. For example: where to collect air sample and how often? How much air volume to collect? Will the sample require storage prior to analysis? How will the sample be analyzed? And importantly, which air sampler to use?
 

Choosing the Right Air Sampler

The design and efficiency of the air sampler can have a big impact on the study’s success. In general, compact and portable air sampling devices are most practical for field work. Dependence on an electrical outlet is also inconvenient, so cordless devices with a long battery life are ideal.
  
Sartorius’s MD8 air samplers have been used extensively during the COVID-19 pandemic to monitor patient rooms, ICUs, waiting rooms, and other public areas in health care facilities. The water-soluble gelatin membrane filters really simplify the workflow and provide the highest retention rates for bacteria, viruses, spores, and phages. They also maintain the viability of sampled microorganisms, which is necessary for viability and infectivity assays.   

In a recent collaboration, an Indonesian-based microbiome and microbial diagnostics company successfully tested an MD8 air sampler to detect SAR-CoV-2 in a mosque, cinema and school.
 

  Validation of an Airborne SARS-CoV-2 Surveillance System in a Controlled Space, Cinema, and Mosque in Indonesia

Wastewater Monitoring for Microorganisms

Wastewater testing is another effective method for early detection of outbreaks in a specific region, for example a city, neighborhood, or building. This approach has been instrumental in tracking SARS-CoV-2 and its variants during recent surges. 

In a typical protocol for SARS-CoV-2, sample is collected before sewage is treated at the treatment plant. Next, the sample is pre-treated and processed via filtration and concentration steps to isolate viral RNA for RT-PCR analysis. Sample preparation using reliable ultrafiltration products and fast-flow membranes helps to speed up the process and produce high-quality sample.

^{Note: Vivaflow®️ Tangential Flow Filtration Cassettes for high-recovery virus concentration.}

Environmental Testing Is the Future

There is mounting evidence in favor of environmental monitoring as part of an effective public health strategy during an outbreak, or for tracking future infectious disease trends. Over the last two years, Sartorius has worked extensively with customers to develop effective solutions for environmental monitoring, not just for COVID-19, but also other microorganisms —and that’s a good thing, since air and water testing is here to stay.