In recent years, there have been several serious viral infectious diseases, including SARS, MERS, Ebola, Marburg and the current COVID-19 virus, and the origin of these viruses is closely related to bats, so bats are called “poison kings.” According to research, human influenza viruses basically come from poultry. It is difficult for viruses from oviparous animals to infect mammals, but bats have broken the boundaries of this species, and bats are the only mammals that can fly.
Scientists have found that the body temperature of bats is higher than that of other mammals, similar to birds, reaching 38-41 degrees Celsius. When the human body is sick, in order to prevent the survival and reproduction of the virus, our immune system will actively increase the body temperature of the human body, so that the virus cannot reproduce, and even achieve the purpose of killing the virus. The body temperature of a bat is exactly the body temperature of a human being with a high fever, so when the virus encounters a bat, the high temperature will prevent the virus in the bat from reproducing on a large scale. Therefore, although bats carry many viruses, these viruses can “live in harmony” with them.
On the other hand, researchers at the University of California, Berkeley found that bats do not kill viruses, but shut down cells and expel the viruses. It is understandable to excrete viruses in order to survive, but the process of bat detoxification enhances the infectivity and toxicity of viruses to humans (Corona virus outbreak raises question: Why are bat viruses so deadly? Science Daily, 10 February 2020).
The virus must invade the cell to survive and reproduce. Studies have found that when the virus enters the bat, the cell responds quickly to the virus infection, shuts down the cell, and prompts the virus to escape from the cell. Although this can protect bat cells from a high number of virus infections, it also induces the virus to replicate and multiply faster, making the bat itself a reservoir for rapidly multiplying viruses. The bat immune system can also trigger the “interferon-α” signaling molecule, thereby reducing inflammation related to the antiviral immune response. After humans suffer from new coronary pneumonia, the immune response is easily out of control and fiercely attacks normal lung cells, resulting in an outbreak of inflammatory factors.
Although the bats that are “one foot taller” successfully resist the virus, the viruses that are “one foot taller” have also gained higher toxicity. When these viruses that have been “experienced” by the bat’s immune system enter animals (such as humans) that lack a rapid immune response system, they will quickly and completely occupy the host cells, resulting in high mortality. Researchers say that the destruction of bat habitat by humans puts pressure on bats, prompting them to release more viruses in their saliva, urine and feces, which may infect other animals.
Viruses in bats are generally transmitted to humans through animal vectors. Therefore, close contact between animals and people in enclosed spaces should be avoided. For example, the farmer’s markets in the past were all open-air, but now they are basically indoors, and the air flow is not smooth, which may make the vegetable market one of the reasons why the virus originated. Viral infections generally disappear on their own within a certain period of time. One reason is that the virus rapidly mutates to coexist peacefully with the human body, and the other reason is climate change. In fact, patients with the new coronavirus in a ventilated environment are more likely to heal, indicating that the microclimate in the personal environment is also important for preventing and controlling viral infections.
