The COVID-19 virus spreads mainly from person to person when someone with the virus coughs, sneezes or talks. The virus sends out tiny, disease-causing particles into the air. These particles can land on other people’s hands, noses or mouths. They can also go into a room or building and infect people who are nearby. These people will probably have cold-like symptoms and may have a sore throat or cough. They will be contagious to other people for two to 14 days.
A blood test can show if you have been exposed to the virus or have the virus in your body. But it takes at least 12 days after exposure for the antibodies to show up on a blood test. Only then can you be sure that you have the active infection, which can cause serious illness.
Some COVID-19 variants are more dangerous than others because of changes in their ability to spread and make people sick. These are called “variants of interest” or “variants of concern.”
Scientists study COVID-19 variants to learn more about how they work and how to protect people from them. They look for changes in a protein on the surface of the virus that helps it attach to and infect cells. They also look for mutations that let the virus evade protective antibodies induced by previous infection or vaccination or detection by testing methods.
The most widely circulating variant is Omicron, which has been very difficult to eradicate. It is highly mutated and has several mutations in the spike protein that allow it to escape from vaccine-induced, natural, and hybrid antibodies.