The flu once started off something like covid 19, but the thing with coronaviruses is that they change quickly. The goal of a disease isn’t to kill its host (whoever it has infected), but to reproduce. How the virus reproduces and how it spreads is what causes people to get sick, as the process damages important parts of the body and processes in the body.

So when a virus is new, it is sometimes too aggressive and makes the host very sick or even die. This means the virus dies with the person. But over time as the virus spreads, it learns better ways to hop from person to person (transmit) and better ways to replicate while keeping its host well enough to spread the disease.

Variants like Delta and Omicron are the virus’s way of trying to become as transmissible as possible so it can infect lots of people. Remember, its goal is to spread, not to kill. There are two problems with this. 

The first is that the more transmissible a disease is and the more people catch it, it can increase the chances that vulnerable people catch it and are seriously ill. Some vulnerable people have hidden or underlying vulnerabilities they might not know about, so it’s not always older people or sick people who are the most vulnerable. Even if a disease seems mild to healthy people, it can be a serious risk to vulnerable people. So very transmissible diseases are a concern even if they don’t seem to cause serious illness.

The second problem is that when the virus changes, it doesn’t always get less deadly. Sometimes viruses can increase in transmission and in danger. This is a big problem because it increases the chances that more healthy people will get seriously ill too.

Scientists want to understand how coronavirus changes so they can understand how much of a threat it is, and so they can keep changing the vaccine and medicines to be more effective against coronavirus.

This section has been fact checked with GAVI. Gavi, the Vaccine Alliance helps vaccinate almost half the world’s children against deadly and debilitating infectious diseases. Gavi’s impact draws on the strengths of its core partners, the World Health Organization, UNICEF, the World Bank and the Bill & Melinda Gates Foundation, and plays a critical role in strengthening primary health care (PHC), bringing us closer to the Sustainable Development Goal (SDG) of Universal Health Coverage (UHC), ensuring that no one is left behind.