The leftovers of coronavirus that were found in the sewage water ‘fit’ suspiciously well on the cells of rats and mice, except for human cells. That is yet another indication that the coronavirus can hide in animal populations from which, in altered form, it can at some point reinfect humans.
Also with the omikron variant, one of the hypotheses is that it is a variant that ended up in mice or rats, developed there under the radar, and then jumped back to humans. In Denmark and the Netherlands, among others, the virus, mutating and well, went around among minks. It would turn corona into something like the flu: a virus that periodically fires new variants from the animal kingdom at humans, for which the immune system is not yet well prepared.
In the Netherlands, too, people are considering further research into whether the corona virus circulates in rats, says virologist Marion Koopmans. ‘It’s an interesting hypothesis. But to prove it, you would also have to take samples from the animals. In any case, this research just shows what fascinating things you can find by studying sewage water.’
Building instructions
For their study, virologist John Dennehy of the City University of New York and colleagues spent months collecting samples of the wastewater from 14 sewage treatment plants in the city. There they found, among other things, the genetic building instructions for corona protrusion proteins that they did not yet know. In May and June, when the epidemic was at a low ebb, the secretive variants made up the majority of what was found in coronaviruses.
This may indicate that there are still undiscovered variants circulating among humans. But since the ghost variants keep appearing at the same sewerage installations, have not yet been found anywhere in humans and were also abundantly present when there was hardly any corona in humans, it is also quite conceivable that ‘these virus families originate from an animal host, for example a rodent’. , as the team cautiously puts it in trade magazine Nature Communications.
Follow-up experiments in the lab grew four of the puzzling protrusions of fake virus particles to better understand their function. Two of the protrusions turned out to be able to shake off antibodies completely, two others partially did. That makes them “potentially dangerous to human health,” Dennehy said.
Rat versions
Koopmans finds the new research ‘fascinating’ and ‘super interesting’. After the first corona wave, Koopmans’ group found also unknown pieces of mutated coronavirus in the Dutch sewer. That does not necessarily mean that there are ‘rat versions’ of corona, she emphasizes. It is much more obvious that these are mutated human coronaviruses that have simply not yet been discovered.
But it does indicate how useful it can be to flea the sewer molecularly, says Koopmans. Together with international colleagues, her group is working on a so-called ‘virome’ of the world’s sewers, a sample card that indicates roughly which sewer contains which viruses. Hopefully that can one day work as a radar, to detect new germs earlier.
Omikron variant
It is striking that some of the ghost viruses from the New York sewer look suspiciously like the omikron variant. This could indicate that evolution in completely different places on the globe is sometimes ‘pushing’ the coronavirus in the same direction, a well-known phenomenon.
What argues against the rat theory is that no remnants of corona have yet been found in rat feces or in blood samples from the animals in New York. “Maybe we just haven’t researched the right animals yet,” Dennehy told US journalists.