Sewage Measurements Predict COVID-19 Trends
A recent blog posting reported that
researchers in the Netherlands were the first to find that the
SARS-CoV-2 coronavirus, which appeared in late 2019,
could be detected in municipal wastewater systems before cases were
officially detected and reported by public health systems.
Soon afterward, researchers in France found that the levels of
viral genetic material in untreated sewage closely tracked
increases and decreases in case loads.
Actually, it anticipated clinical case trends.
France had a rapid rise in cases, and then aggressive lockdown and
social distancing caused the new case rate to drop.
Their measurements of SARS-CoV-2 genetic material in the Paris sewage
clearly showed what was about to happen in public health numbers.
The SARS-CoV-2 coronavirus
was spreading world-wide in early 2020.
It causes the severe acute respiratory syndrome
known as COVID-19.
The general public and the media referred to both the virus and the disease
COVID-19 can lead to a life-threatening pulmonary condition
similar to pneumonia.
If the patient's immune system over-reacts,
as happens in the worse cases, the lungs begin to fill with fluid.
A Paris sewer tunnel.
Musée des Egouts de Paris
or the Museum of the Paris Sewers
takes you into this subterranean realm of science and Jean Valjean.
How the Virus Spreads
SARS-CoV-2 is spread by people shedding viral particles in their breath,
when coughing or even just breathing, within a range of two meters or less.
The primary human-to-human transmission mode is by respiratory droplets,
and also via fomites (skin cells, hair, clothing, bedding).
Unfortunately, infected people are contagious well before becoming symptomatic.
A significant fraction of patients shed the viral RNA in feces.
That hasn't been a significant vector of transmission,
but it can allow us to detect it.
The New Paper
Science has a nice
Or, you can read the actual preprint at medRχiv.
Experts expect a second wave of outbreaks, as lockdown and isolation
is prematurely ended.
Monitoring of SARS-CoV-2 genetic material would predict that.
Sewers collect feces containing coronavirus shed by infected humans.
Once outside the human body, the virus degrades quickly.
The virus is encased in a lipid outer layer, so soap will kill it.
Or, given that a virus isn't alive in the literal dictionary sense,
Detergents coincidentally mixed into the sewage will
start breaking down virus particles.
This sewage surveillance work, like other projects,
looks for fragments of viral RNA.
This project collected samples of both raw and treated wastewater
from three major wastewater treatment plants.
These plants treated waste flows from three to four million
residents of the Paris area.
The viral load was reduced by a factor of about 100 in the treated material.
The lipid coat had been destroyed and the viral RNA broken down.
They detected high concentrations of viral RNA for several days
leading up to 10 March 2020, the first day that Paris recorded
multiple deaths caused by COVID-19.
These concentrations rose for a few days before an acceleration in
clinical cases of COVID-19 and deaths in Paris.
A study co-author said:
"We have a very clear curve that precedes the curve in numbers of
clinical cases, and now with confinement, we see a flattening
of that curve."
Researchers estimate that it takes from a half a day to three days
for sewage to move from residential toilets to the treatment plants.
Given the delay between infection and presence of symptoms,
detection of SARS-CoV-2 genetic material still provides a few
days advance warning of the coming symptomatic trends.
In the U.K., Cranfield University's Water Science Institute is developing
a low-cost test for SARS-CoV-2 in sewage.
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