Schools may have had more Covid-19 infections before Christmas than previous research showed, based on data from a pilot study that public health experts believe could provide a crucial early warning system against future outbreaks.
Covid was present in the sewage of 80% of 16 primary and secondary schools in England during December, and researchers detected the virus about a week before community testing, according to Mariachiara Di Cesare, senior lecturer in public health at the University of Middlesex, who led the study.
“In the first weeks, it was around 20% [of schools]”She said.” Starting in late November, we saw an increase in the percentage that tested positive. And that was in line with a week delay before what was happening in the community. “
Di Cesare and other researchers from Term, a collaboration involving universities and the Joint Center for Biosafety, saw a steady increase to 50% and then 80% of the schools participating in the project, at a time when cases to national level seemed to be declining. “We were very concerned, but the samples were consistent across the school and other schools in the area, so we could see that the virus was circulating,” he said.
Di Cesare wanted to emphasize that the study, which took samples every five minutes from each school’s sewer pipe for eight hours a day, had attempted to show that sewage could be used to discover Covid outbreaks, rather than its scale or how. it could be the transmission. happening.
“This is not data that we would expect to be used to close a school,” he said. “One of the problems we are working on is how to communicate the data to public health teams.”
The small sample size also means that the study may not be representative of schools in England. A study conducted by the Office for National Statistics of 105 schools in November, using PCR tests, found the virus in 55% of schools on a test day, although he also said that the data cannot be used to extrapolate to all of England.
However, because sewage appears to provide early signs of Covid infection, public health officials believe it is better and cheaper than relying on PCR or lateral flow testing.
Maggie Rae, president of the School of Public Health, said that having an effective early warning system was vital to preventing new outbreaks. “Test and trace is not cost effective and it is not an early warning system,” Rae said. “The tests do not tell us how many people have contracted the virus, only those who have come forward for a test,” he added.
“The sewage can give you a very good idea of unknown infections that you can then track down.”
Public health teams from local authorities could identify an area where Covid could be about to break out and go door-to-door offering advice, support and testing kits, he said.
Water supply and sewage systems have been used for public health since John Snow, a London physician, demonstrated in 1854 that cholera was spreading from a well in Soho.
The National Wastewater Epidemiology Surveillance Program began analyzing last summer whether Covid could be reliably detected in wastewater, taking samples at 96 treatment plants in England, Wales and Scotland.
Andrew Singer, who runs N-WESP, said they were able to detect Covid in the sewer system when at least one in 10,000 people is infected – about 15 people in a city the size of Oxford.
The growth of new variants of Covid is also detectable, he said. “You can get an early look at the variants of interest and quickly assess how concerned we should be about them.”
The program is expanding to more than 200 sites in England, covering 80% of the population. Wastewater is routinely screened in Australia for Covid outbreaks, and before pandemic wastewater testing was part of UK polio and norovirus screening.
“We have the oldest sewer network in the world, practically. If you compare it to the one in Australia, which has pipes that are 20 years old and documentation showing where they are, to be honest I’m envious of how easy it is. “
George is Digismak’s reported cum editor with 13 years of experience in Journalism