With home Covid-19 tests in high demand and their effectiveness questioned, health departments from California to Massachusetts are turning to sewage samples to get a better idea of ​​the extent of the coronavirus spread in communities and what might be in store for health care systems.

Experts say wastewater holds the key to better understanding the public health of cities and neighborhoods, especially in underserved areas that do not have equal access to care.

“Every time an infected person uses the toilet, they throw that information down the toilet, where it is collected, aggregated and mixed with the poo of thousands of other people,” said Newsha Ghaeli, co-founder and president of Biobot. Analytics. , a Massachusetts-based wastewater epidemiology company.

“Even if you can’t get to a test, you’re still pooping,” Ghaeli said. “It doesn’t depend on your access to health care or health insurance. “

Wastewater monitoring can also measure other public health issues, such as obesity, opioids and even polio, said Sheree Pagsuyoin, associate professor of civil and environmental engineering at the University of Massachusetts Lowell. The pandemic has ushered in a new era of wastewater analysis, once a disparaged discipline, to inform public health policies.

“It’s a bit like mapping a trend,” Pagsuyoin said, adding that there has been a “paradigm shift” as more cities turn to wastewater analysis to better understand the local challenges.

A recent analysis of sewage from various sources across the country indicates an unprecedented rise in infections at a time when millions of people are forced to reconsider their travel and vacation plans.

According to Biobot Analytic’s wastewater dashboard, the levels of Covid-19 detected in wastewater samples across the country are higher now than at any time prior to the pandemic.

Recent sewage samples in Houston, for example, show that there has been a sharp increase in the amount of coronavirus detected in the city’s sewage. As of December 20, Houston’s viral load, or the amount of virus found in samples, was 546% and the positivity rate was 14%, according to the city’s Department of Health Wastewater Dashboard. . Viral load is up from 142% last week and 76% the week before.

More than 700 city workers have contracted the virus, Mayor Sylvester Turner said on twitter. As a result, Turner announced the opening of two additional megasites that will offer free testing to residents.

Dr Amesh Adalja, Principal Investigator at the Johns Hopkins Center for Health Security, said: “Wastewater is going to be a leading indicator of what is going on in any given community.

“It will also give an indication of what is to come, as not all cases of Covid are clinically reviewed – many cases are mild or asymptotic,” he added. “But the point is, people who are infected will excrete the virus in their stool. “

Sewage monitoring also shows that the number of cases is increasing in parts of California, Colorado, Idaho, Massachusetts, Missouri and North Carolina, as well as in Canada, Spain and the United States. UK.

A team of researchers from the University of Missouri worked with the Department of Health and Seniors Services and the Department of Natural Resources to track the virus in wastewater.

Researchers in Missouri separate the virus from larger particles of waste and extract its genetic material. They can also amplify genetic material and study it in more detail through a process known as the quantitative reverse transcription polymerase chain reaction. In addition to detecting the presence of the virus that causes Covid-19 in human waste, researchers are also able to identify specific variants.

New data shows that the highly contagious variant of omicron is spreading rapidly throughout the state.

Extensive testing on Dec. 20 found mutations associated with the omicron variant in 32 of 57 sewage samples collected statewide, Jeff Wenzel, who oversees the water monitoring program, told The Associated Press. used for the state health department. Tests carried out the previous week found the mutation in 15 of 63 test sites.

Pagsuyoin is part of a Massachusetts team developing a wireless sensor that could detect SARS-CoV-2, the virus that causes Covid-19, in the air and wastewater days before an epidemic hits happen. Researchers will undertake a three-year study using data from three monitoring sites, two of them in Massachusetts and one in the Philippines.

“People are becoming a little more open to using wastewater data to find out where a disease is supposed to come from,” she said. “We can use this technology to more effectively monitor the health of the population. “

Wastewater testing is more effective as an early warning signal between surges – especially because people don’t test as often when rates are dropping – and in tracking when the waves start to dissipate. . It can also help fill in some gaps during waves when testing is insufficient and serve as a way to compare waves, said Dr Albert Ko, professor of public health, epidemiology and medicine at the School of Public Health. from Yale University.

“What’s useful is looking at trends over time and comparing, say, ‘Are we as bad at transmitting this wave compared to the last? Such comparisons.

Ko said wastewater monitoring is best used as part of a larger analysis of an outbreak that takes into account other data points, such as testing.