Virus World

Scientists say samples from Milan and Turin showed virus traces long before cases were confirmed. Italian scientists say sewage water from two cities contained coronavirus traces in December, long before the country's first confirmed cases. The National Institute of Health (ISS) said water from Milan and Turin showed genetic virus traces on 18 December. It adds to evidence from other countries that the virus may have been circulating much earlier than thought. Chinese officials confirmed the first cases at the end of December. Italy's first case was in mid-February.

In May French scientists said tests on samples showed a patient treated for suspected pneumonia near Paris on 27 December actually had the coronavirus. Meanwhile in Spain a study found virus traces in waste water collected in mid-January in Barcelona, some 40 days before the first local case was discovered. In their study, ISS scientists examined 40 sewage samples collected from wastewater treatment plants in northern Italy between last October and February. Samples from October and November came back negative, showing that the virus had not yet arrived, ISS water quality expert Giuseppina La Rosa said. Waste water from Bologna began showing traces of the virus in January. The findings could help scientists understand how the virus began spreading in Italy, Ms La Rosa said.

However she said the research did not "automatically imply that the main transmission chains that led to the development of the epidemic in our country originated from these very first cases". 

Italy's first known non-imported virus case was a patient in the town of Codogno in the Lombardy region. The town was closed off and declared a "red zone" on 21 February. Nine other towns in Lombardy and neighbouring Veneto followed and the entire country went into lockdown in early March....

Microbiologists at research institute KWR conducted a series of RNA-analyses at municipal waste water treatment plants (WWTP) in the Netherlands. The analyses showed the presence of RNA gene fragments of the COVID-19 virus in incoming sewage water. According to KWR the screening of the COVID-19 virus at municipal waste water plants can be used to signal new outbreaks in advance and play an important role to follow the evolution of the pandemic.

RNA-analysis is a method to measure the presence of viruses through capturing virus particles and detect specific gene fragments. The method does not discriminate between inactive and infectious particles. The KWR microbiologists say they have not yet been able to quantify the presence of these fragments. Their first findings indicate that the concentration of the virus at the WWTP is low.  Currently researchers are examining all samples multiple times and are looking at the reproducibility of the results. Furthermore, they double check and focus on fragments of multiple genes, to strengthen their results about the presence of the virus. The detection of COVID-19 in the sewage water at the Dutch WWTP does not really come as a surprise. Sewage water contains many viruses and the detection of the new coronavirus from human faeces was to be expected. Study results released by Chinese microbiologists in 2005 showed that SARS-CoV RNA had been detected in the sewage water of Chinese hospitals where SARS-patients were treated.

KWR suggests the use of the RNA-analyses of the SARS-CoV-2 in sewage water as a tool to measure the virus circulation in cities or smaller municipalities. The concentration level of the virus can be an indicator for the number of virus infections in the population and can signal in advance a new outbreak, for instance when a lock down is lifted. Similarly, these analyses can help monitor the effect of measures put in place to mitigate the spreading of the pandemic, according to KWR.

By sampling sewage across greater Paris for more than 1 month, researchers have detected a rise and fall in novel coronavirus concentrations that correspond to the shape of the COVID-19 outbreak in the region, where a lockdown is now suppressing spread of the disease. Although several research groups have reported detecting coronavirus in wastewater, the researchers say the new study is the first to show that the technique can pick up a sharp rise in viral concentrations in sewage before cases explode in the clinic. That points to its potential as a cheap, noninvasive tool to warn against outbreaks, they say.

“This visibility is also going to help us predict a second wave of outbreaks,” says Sébastien Wurtzer, a virologist at Eau de Paris, the city’s public water utility. Wurtzer and his colleagues posted the study, which has not been peer-reviewed, on the preprint repository medRxiv on 17 April. Sewers offer near–real-time outbreak data, because they constantly collect feces and urine that can contain coronavirus shed by infected humans. (Once excreted from the body, the virus degrades quickly, although scientists have found limited instances of infectious virus in fecal matter.) Polymerase chain reaction testing identifies fragments of RNA from SARS-CoV-2, the virus that causes COVID-19. Higher concentrations of virus in the wastewater corresponds to higher numbers of infected people who contribute to the sewer system.

For the Paris study, Wurtzer and his colleagues sampled wastewater from up to five Paris-area plants twice a week between 5 March and 7 April. They noted “high concentrations” of viral RNA several days before 10 March, the first day that Paris recorded multiple deaths from COVID-19. Concentrations continued to rise a few days ahead of an acceleration in clinical cases and deaths in Paris. “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,” says Laurent Moulin, a study co-author and a microbiologist also at Eau de Paris. He estimates it took between a half a day and 3 days for the sewage to move from toilets to the treatment plants.

Preprint available at medRXiv (April 17, 2020):

https://www.medrxiv.org/content/10.1101/2020.04.12.20062679v1