With coronaviruses like SARS, MERS, and now COVID-19 thought to have originated from bats, the question arises how these mammals carry the virus without getting sick themselves. While these diseases have proven fatal for humans, it has not affected the bat population. In fact, bats neither get rid of the virus nor do they get sick. Now a group of Canadian scientists may have found the answer to this mystery. According to their research, published in Nature Scientific Reports, the reason could be ‘super immunity’ in these mammals, which allows them to carry the virus without any harm. 
To understand the virus’s interaction with its host, the team established a long-term infection model by persistently infecting bat cells with MERS-CoV. These infected cultures were maintained and studied for at least 126 days. The team studied the infection progress and pattern in bat cells. They found that stress to their immune system causes disruption in the virus balance in their body, allowing the latter to multiply.
The bat cells then adapt. But instead of triggering inflammation that results in sickness, the infected bat cells respond through a natural antiviral action. The MERS virus also starts adapting to the host. It starts mutating one specific gene. This dedicated balance can exist long-term till a disruptor, such as a disease, upsets it. The team found that bat cells that were infected persistently developed resistance to superinfection by wildtype virus.
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