skip to main content

What Are Virus Variants?

Learn how viruses mutate to create variants, such as Delta and Omicron, and how vaccines work against variants.

What is a Virus?

Viruses occupy a gray area between the living and nonliving realms. Scientists have identified more than 200 virus species with the potential to infect humans.

How Do Viruses Infect Our Cells?

New viruses are discovered every year, and some, such as SARS-CoV-2, cause disease. Explore the mechanics behind infection.

How Do Viruses Spread?

Learn about the multiple pathways through which virus transmission can occur and how SARS-CoV-2, the virus that causes COVID-19, is spread between people.


How Do Masks Work?

While face coverings primarily prevent the wearer from spreading the disease, they also can protect the wearer from others. Two lines of evidence support the effectiveness of face coverings in reducing the spread of COVID-19.


How Do Vaccines Work?

Vaccines are powerful and effective tools for preventing and slowing the spread and reducing the severity of disease.


How Are Vaccines Developed?

Careful testing is necessary to ensure new vaccines are safe and effective. Learn how scientists create vaccines, and why the process takes as long as it does.


What Is Passive Immunization?

Find out how antibodies from other sources can be used to provide short-term protection against infection.

How Does COVID-19 Testing Work?

Accurate testing is necessary to better control the spread of diseases like COVID-19. Learn the difference between PCR, antigen, and antibody tests.


How Do Antivirals Work?

Antivirals are medications used specifically to treat viral infections. Learn how scientists develop treatments for diseases such as COVID-19.

How Does Disease Modeling Work?

Models help policymakers forecast the spread and severity of disease. How do researchers create them?

Ask a Caltech Expert

Experts in immunology, aerosols, materials science, and more answer the public's questions about science-based solutions to the coronavirus pandemic. Learn about booster shots, antibody treatments, and masks.

Terms to Know

Dive Deeper