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.

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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.

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FIGHTING VIRUSES

How Do Vaccines Work?

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

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FIGHTING VIRUSES

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.

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FIGHTING VIRUSES

What Is Passive Immunization?

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

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Fighting Viruses

How Does Coronavirus Testing Work?

Accurate testing is necessary to better control the spread of diseases like COVID-19.

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Fighting Viruses

How Do Antivirals Work?

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

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How Does Disease Modeling Work?

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

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Ask a Caltech Expert

Professor Pamela Bjorkman on SARS-CoV-2

Pamela Bjorkman, Caltech's David Baltimore Professor of Biology and Bioengineering, answers questions from the public on viruses, antivirals, and vaccines.

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Terms to Know

Also known as immunoglobulin (Ig), a protein in the blood and component of the immune system used to fight pathogens (microbes that cause illness).

A test that looks for an antibody response to a specific pathogen, indicating that an individual has previously been infected. Learn more about antibody testing.

A foreign substance that triggers an immune response in the body.

A type of therapeutic used to treat a viral infection. Antivirals do not work against bacteria just as antibiotics do not work against viruses.

A process used to identify people who may have come into contact with a person infected with a disease and are thus at a higher risk of becoming infected themselves.

A family of viruses that have a crown-like appearance and cause illnesses ranging from the common cold to severe diseases such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV).

The disease caused by the novel coronavirus, SARS-CoV-2. COVID-19 is short for "Coronavirus Disease 2019."

A coordinated effort to slow the rate of new infections so that hospitals and other service providers have time and resources to respond to an outbreak. The "curve" refers to the shape, plotted on a graph or chart, depicting new infections over time.

Resistance to the spread of a contagious disease within a population as a result of a high proportion of individuals developing immunity.

The time between exposure to a virus and the emergence of symptoms or signs of illness. COVID-19 has an incubation period of two to 14 days. In most cases, symptoms appear about five days after infection. People can have COVID-19 and experience few to no symptoms.

One of a group of "nucleic acid amplification tests" that looks for the presence of viral genetic material in the body. They are used to diagnose active infections. Learn more about PCR testing.

In the context of disease, it is the act of isolating oneself due to the presence of symptoms. It is a means of controlling the spread of disease.

The practice of maintaining distance from or avoiding physical contact with others in an attempt to prevent the spread of disease.

Dive Deeper

Scientist Christopher Barnes seated at a lab bench and pipetting with gloves on
Images of Antibodies as They Neutralize the COVID-19 Virus
David Ho portrait with Coronavirus background
The Tip of the Iceberg: Virologist David Ho (BS '74) Speaks About COVID-19
SARS-CoV-2 artist's representation in lime green, fuschia, white, and yellow
Merkin Institute Catalyzes COVID-19 Research at Caltech