How did the Covid-19 start?
Who or what is to blame for Coronavirus pandemic? There have been several theories regarding the emergence of Covid-19. From the conspiracy theories of it being deliberately manufactured in a lab in China, escaping from a lab to coming from Chinese wet food markets. Many of these theories all involve bats in one way or another.
Indeed this wouldn’t be the first time that coronaviruses from bats have spilled over into human populations. This has occurred several times in the past. it’s likely that this won’t be the last time that this occurs. The Covid-19 outbreak has become a worldwide public health problem so it is not surprising that people are seeking an answer to just where Covid-19 came from.
Are Bats To Blame for Covid19?
Nature Reviews Microbiology, published a study into bat coronaviruses. They looked at the ecology and evolution of coronaviruses and how they could spillover from bats to other hosts, including humans.
Distribution of bat coronaviruses
- Coronaviruses have been detected in 16% of bat species.
- There are 21 bat families, and alphacoronaviruses and beta coronaviruses have been detected in 14 bat families in at least 69 countries across six continents.
- The apparent absence of coronaviruses in particular bat families is likely due to insufficient sampling rather than true absence.
- Viruses with high sequence similarity to the three recently emerged human coronaviruses have all been identified in bats. These include severe acute respiratory syndrome coronavirus (SARS-CoV), SARS-CoV-2, and Middle East respiratory syndrome coronavirus (MERS-CoV).
Do bats suffer from Coronavirus?
Coronavirus infection in bats
There has only been a few studies into the effect of coronavirus infections in bats themselves. Some of those studies showed mild tissue damage, swelling of the nasal mucous membrane, and lung infections in the bats. The virus or viral RNA could be detected in the respiratory tract and/or intestines. However, the infected bats did not exhibit evident clinical signs of infection.
Do bats get an immune response to coronavirus infections?
There are very few studies, and bats do not always produce antibodies against the virus after infection. Bats have limited humoral responses, making it difficult to use serum antibody levels to identify infections by certain pathogens. In bats, coronaviruses may have the ability to infect the respiratory tract and the gastrointestinal tract.
Several in vitro studies provide insights into the spillover potential of specific viruses, but they provide limited insight into bat susceptibility at the organismal level. Moreover, studies making such inferences should be interpreted with caution because whether those viruses cause persistent infections in bats cannot be predicted without in vivo studies.
Are coronaviruses common in bats?
To prove that coronavirus is present in bats it is necessary to detect the viral RNA in fees or oral swabs. Studies have shown that this varies through the year and in differing locations. In China it is primarily in summer or autumn. in Central Africa and Asia it is highest in dry seasons yet in West and SE Africa it is higher in wet seasons.
The incidence is likely influenced by the age and species of bats and the colony size. Different species of bats often roost together. If the roost size is dense then infection and spillover are higher. It is not uncommon for bats to suffer from more than one coronavirus species at a time.
Do bats give Coronavirus to humans?
The evidence of bats giving the virus to humans is not conclusive. In most cases bats and humans mixing happens in rural areas and often in poorer countries. It is possible that infections go undetected because they are not investigated. As the recent pandemic has shown the effects vary from one individual to another and can be asymptomatic.
It could be that other animals are acting as intermediate hosts to transfer the infection to humans. These intermediate hosts can allow for the virus to evolve and increase in load making the transmission to humans more likely.
Previous studies into Coronavirus transmission looked at SARS-CoV-2 and how that was transmitted to humans. The first SARS-CoV-2 transmission event may have happened directly from bats or through a bridging host. Most likely, it was a direct bat-to-human transmission.
We shouldn’t forget that humans can also act as bridging hosts. Humans have infected domestic cats and dogs with SARS-CoV-2, potentially acting as reservoirs for new variants. More recently it was shown that a pet owner in the UK gave Covid to their pet dog.
While some of the evidence is not proven it seems probable that bats are responsible for the transmission of Covid-19 to the human population. Whether a market or a lab was responsible for the initial event may never be resolved.
However, if you are looking for someone to blame for Coronavirus it is hard to remove bats from the equation as a likely source.
