Snapshot from sewage

Wastewater surveillance is a cheap and effective way to map the spread of infection, be it COVID-19 or any other pathogen

- TARAN DEOL

LAST YEAR, as the world was inching closer to the possibillity of returning to normality after fighting the pandemic for two long years, the emergence of Omicron, with its 32 mutations on the spike protein, dampened all hope. The US was among the first few countries to ban travel from South Africa, which first reported the COVID-19 variant, and its neighbouring nations. Despite its efforts, the US on December 1 reported its first case of Omicron through clinical testing.

However, just a few days later, a routine wastewater surveillance being conducted by the US' Centers for Disease Control and Prevention (CDC) showed that Omicron may have been present in the country well before being reported in December. The surveillance provided a clear snapshot of the spread of the variant in California, Colorado, New York City (New York) and Houston (Texas).

Sewage samples collected from these areas between November 21 and December 16 showed that "the detection of Omicron-associated mutations in community wastewater provides strong early evidence that the Omicron variant was likely present or more widely distributed in these communities than originally indicated by clinical testing," says CDC. The National Wastewater Surveillance System (NWSS), established by CDC in September 2020, collects over 34,000 samples every day, representing an estimated 53 million American citizens. "These data are uniquely powerful because they capture the presence of infections from people with and without symptoms, and they are not affected by access to healthcare or availability of clinical testing," Amy Kirby, program lead for NWSS, said in a media report in early February.