A new Tel Aviv University study rejects assertions that the origin of the COVID-19 outbreak is in bats. According to the study, the species did not transmit the first strain of the virus to humans because of its highly effective immune system that easily fights viruses considered lethal for other mammals.
Many viruses carried by bats cannot infect humans without first undergoing evolution, meaning that they carry the ancestral virus and not the human pathogen. Therefore, another animal had to have transmitted the virus from bats to humans.
Bats are known as natural reservoirs – a living species inside which a pathogen survives, often without causing disease to the organism itself – and have been thought to transmit numerous infections to humans. Although it had been believed that they have transmitted over 100 infections to humans, the researchers found that an identical and viable pathogen was never isolated from the species in around 50 per cent of the viruses.
For example, bats are often accused of being the reservoirs of Ebola. But studies have found that they do not permanently host the Ebola virus, and that the prevalence of antibodies in the bat population is very low, at three per cent. In comparison, the prevalence of avian flu in birds, another reservoir species, is much higher.
“In general, bats are mistakenly conceived of as reservoirs of many contagious disease, only due to their being serologically positive; in other words, in possession of antibodies, which means that bats have survived the disease and developed an immune response,” said Dr. Maya Weinberd, the researcher who led the study.
“After that they overcame the virus altogether and disengaged from it; hence, they are no longer its carriers. Nevertheless, in many cases, a virus similar to a human pathogen is liable to be found in bats; however, it is not pathogenic to humans, and is not sufficient to use bats as a reservoir.”
“The comprehensive study we’ve conducted raises serious doubts regarding the possibility of bats being the origin of the COVID-19 outbreak.
“The findings give rise to the opposite perspective, according to which we must study in-depth the immunological anti-viral capabilities of bats, and thus obtain new and effective means of coping in humanity’s struggle against contagious disease, aging and cancer.”