Most people are not aware that they are regularly infected with hundreds of viruses, because the vast majority cause no illness at all. For example, studies of autopsies have demonstrated that around 30 percent of people have live measles viruses in their brain at the time of their death. About the same number harbor the cytomegalovirus and/or herpes viruses.

In addition, a large percentage of elderly people are infected with the chickenpox virus. But unless the virus is activated, they remain completely unaware of its presence. (When it is activated, the viral infection called shingles develops.)

Viruses can directly damage and even kill cells by a number of mechanisms. But in most instances, the greatest damage is not caused by the virus itself, but by our own immune system’s reaction to the infectious agent.

To kill a virus, the immune system must act quickly to prevent it from replicating so fast that it overwhelms the immune system. In fact, studies of COVID-19 have found that those who died had very high titers (number of viruses) early in the course of the disease, compared to those who survive or have few or no symptoms.

The higher the titer of viruses, the more intense the immune attack that is required to kill the invaders.

Because speed is everything, our immune system was designed to offer several layers of protection that operate at different speeds.