A startling new study adds to the growing body of evidence that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes COVID-19, the pneumonic illness now sweeping the world, was circulating in Brazil’s Santa Catalina as far back as November 2019. The finding, published on the preprint server medRxiv* in June 2020, shows that it has been causing infection in Brazil long before the first case was reported in the Americas, North and South, in January 2020, and certainly before the first case in this Brazilian region.
Novel Coronavirus SARS-CoV-2 Creative rendition of SARS-COV-2 virus particles. Note: not to scale. Credit: NIAID
The Beginning of the Pandemic
The first cases of atypical pneumonia attributed to the virus causing COVID-19, the SARS-CoV-2, were in Wuhan, Hubei Province, China. Investigators with the China CDC described three adults who were admitted to a hospital in Wuhan on December 27, 2019, with pneumonia cases of an unknown cause.
From there and spreading outwards across all international borders, the virus caused a brief but extremely harsh spell of disease and death in Europe and South Korea, before spreading to the Americas and Asia. At least, that was what most researchers thought.
However, early evidence was mounting that the virus had already been spreading around the world a few months prior to the first occurrence on January 21, 2020, in the USA. The first Brazilian case was diagnosed on February 25, 2020.
Respiratory and Fecal Positivity
The virus is a respiratory pathogen, with transmission being chiefly through respiratory droplets and by touch with contaminated surfaces. The virus is also known to infect gastrointestinal tissues, and fecal samples have shown high and sustained levels of the virus at up to 108 copies of the viral RNA per g of stool.
The use of sewage as a mode of monitoring the presence of SARS-CoV-2 has been applied in earlier research, demonstrating this to be a non-invasive tool to predict the imminence of an outbreak or an upsurge in an endemic infection.
The Study: Seeking the Virus in Sewage
The current study was based on the analysis of human sewage from Santa Catalina, Brazil, beginning from samples collected in late October and continuing until late March. The researchers collected samples of urban sewage in six separate sampling episodes.
The sewage was untreated and came from a sewage system in central Florianopolis, which served about 5,000 people. This system receives only wastewater. The sample consisted of 200 mL and was cultured for the viral load, as well as tested for the viral RNA.
Surprising Positivity of Sewage Before Earliest Known Case
The first two samples were on October 30 and November 6, 2019, and turned out to be negative. Thereafter, all samples were reported to be positive from the virus, beginning from November 27, 2019, to March 4, 2020. The viral load, overall, was 5.83 log10 copies L-1, which is similar to the viral loads in sewage studies in France and Spain, as well as the USA, during active infection.
The striking thing is that the first positive sample preceded the first diagnosed case in the American continent by 66 days and the first known case in Brazil by 91 days. In Santa Catalina, the first case was reported only after 97 days. In other words, the virus was being disseminated in the community months before the first case in North or South America was reported.
Prediction of Future Infection or of Rising in Infection Rates
These findings echo that of earlier Spanish and Italian sewage studies, where the presence of the virus in wastewater was retrospectively studied and found to be positive before the earliest reported cases. Another interesting feature is the relative stability of the viral load until the end of February 2020, at about 5.5 -5.8 log10 copies per liter.
However, on March 4, 2020, the viral titer jumped upward by about one log, to 6.7 log10 copies per liter. This date is significant as that of the first reported case in this region. Ten days later, the Brazilian lockdown came into effect, preventing further sampling, which means the later trends remain unknown.
Implications of the Findings
The researchers say that they have demonstrated that the virus was circulating unnoticed in the community before the number of cases spiked to pandemic levels, or was noticed as such.
Secondly, the viral load remained at a plateau until March 4, 2020, when it rose – at the same time as the first case in Santa Catalina.
The researchers sum up: “This study demonstrates that monitoring of SARS-CoV-2 in wastewater or urban sewage is an excellent tool for anticipating potential epidemiological outbreaks, and would be highly valuable in helping Public Health authorities to define protection measures.”
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.