To fully understand the scope of a pandemic, there needs to be testing.
Counting confirmed clinical cases provides an important view into the scope of this pandemic, but case counts are a dramatic underestimate due to limited access to clinical testing.
Moreover, asymptomatic patients or those with mild symptoms may never seek out testing in the first place, but they are potentially still contagious.
One company is starting to look at a different type of testing - sewage.
Biobot, a company whose mission is to transform wastewater infrastructure into public health observatories, is starting to test major metropolitan area's sewage to try to track COVID-19.
SARS-CoV-2 is shed in stool and has been detected in sewage in the U.S., and in the Netherlands by the KWR Research Institute.
Biobot recently published their first study and the results are shocking. They collected sewage samples from a large metropolitan area in the state of Massachusetts.
On March 25, the area represented by the sample had approximately 446 confirmed cases of Covid-19. Based on our sewage analysis, we estimate that up to 115,000 people are infected and shedding the SARS-CoV-2 virus.
The reason for the discrepancy is not yet clear, however, and until further experiments are complete, these data do not necessarily indicate that clinical estimates are incorrect.
At this time, there’s much work to be done to improve the accuracy of wastewater testing for COVID-19. Beyond technical limitations, there are possible explanations why sewage is giving a higher number of infected people, as compared to confirmed cases:
- People with mild symptoms may not go to the hospital, or get tested,
- There is growing evidence that Covid-19 could have a large asymptomatic population,
- Limited access to clinical testing, and
- A lag in reporting confirmed cases.
However, if successful, this data will give communities a dynamic map of the virus as it spreads to new places.
Data from sewage will enable communities to:
1. Measure the scope of the outbreak independent from patient testing or hospital reporting, and include data on asymptomatic individuals,
2. Provide decision support for officials determining the timing and severity of public health interventions to mitigate the overall spread of the disease,
3. Better anticipate likely impact on hospital capacity in order to inform hospital readiness and the necessity of public health interventions,
4. Track the effectiveness of interventions and measure the wind-down period of the outbreak, and
5. Provide an early warning for reemergence of the coronavirus (if it does indeed have a seasonal cycle).