With health officials trying to prevent and prepare for the spread of the coronavirus in the United States, there is much panic and confusion and many questions. Here are some key terms and facts to know:

Coronavirus: This term refers to a family of seven known viruses that can infect people. They range from coronaviruses that simply cause a common cold to the form that causes severe acute respiratory syndrome (SARS-CoV), which emerged in Asia in 2002, and the even deadlier Middle East respiratory syndrome (MERS-CoV), which appeared in 2012. The name comes from the fact that under a microscope, the virus looks like a blob surrounded by crown-like spikes, a corona.

Covid-19: People are using the term coronavirus, covid-19 and SARS-CoV-2 interchangeably, but those who nitpick will tell you they actually refer to different things. The new coronavirus itself is officially named SARS-CoV-2. The disease the virus causes in people — the fever, coughing, shortness of breath and in severe cases pneumonia and death — is named covid-19. So SARS-CoV-2 causes covid-19, in the same way that HIV causes AIDS.

Zoonotic: The new coronavirus is zoonotic, meaning it was transmitted from animals to people. The SARS coronavirus came from civet cats, and MERS came from camels. It’s not known which animal caused the current coronavirus outbreak. It is a mystery scientists believe they must solve to prevent a future outbreak. The prime suspect so far is the pangolin — an endangered creature that looks like a cross between an anteater and an armadillo.

Community transmission: This refers to cases in which a disease is circulating among people in a certain area who did not travel to an affected area and had no close link to another confirmed case. This is a key indicator for which U.S. health officials are looking out, because it would suggest the virus is spreading in a location in ways that health officials have trouble tracking and containing. To date, almost all cases in the United States have been imported — Americans infected with coronavirus in Wuhan or on a cruise ship in Japan and repatriated to be treated. Or they have been cases of secondary transmission, where a patient from abroad infected a spouse or someone in close contact. But U.S. officials have identified at least one person in California with the virus who did not travel to regions hit by the outbreak or come into contact with previously known patients.

Outbreak: A sudden increase in the number of cases of a disease in a particular place and time.

Epidemic: A large outbreak, one that spreads among a population or in a region.

Pandemic: An epidemic that has become rampant in multiple countries and continents simultaneously. While the word “pandemic” evokes fear, it is mostly a description of how widespread an outbreak may be, not a description of its deadliness. So far, the World Health Organization has held off declaring the current crisis a pandemic, but many experts think the virus’s geographic spread is already at that level or will be before long. A pandemic declaration would be an acknowledgment that this new disease can no longer be contained and that countries need to shift their efforts to minimizing spread and treating the sick.

Fatality rate: Compared with previous epidemics of SARS and MERS, this virus is relatively mild, but it is more severe than seasonal influenza. More than 80 percent of confirmed coronavirus cases are not severe, according to a large study from China using the best numbers available so far. But more than 2 percent of people who are infected die. Some experts think the fatality rate may actually be lower than the estimated 2.3 percent because some cases of the infection are so mild they aren’t being counted. SARS had a 9.6 percent fatality rate, and it was 34.4 percent for MERS. Influenza has a fatality rate of about 0.1 percent, but because it is so widespread, it has already killed as many as 41,000 people in the United States in the 2019-2020 flu season.

Asymptomatic transmission: Asymptomatic carriers of the virus are people who show no signs of being sick but have the virus and can spread it to others. It is unclear how common asymptomatic transmissions are with the new coronavirus, something experts are desperate to determine, because if asymptomatic transmissions are occurring, detecting the virus and stopping its spread will be much harder. And it will mean that testing has to be done on a much larger scale in countries such as the United States.

Isolation: Keeping those who are sick or infected away from those who are not is referred to as isolation. Hospitals have taken strict measures to isolate coronavirus patients using isolation wards, ventilators that prevent air from circulating more widely and heavy protective gear for health workers.

Quarantine: Restricting the movement of people who seem healthy but may have been exposed to the virus is referred to as a quarantine. Americans who were evacuated from Wuhan and cruise ships, for example, have been kept in strict quarantine on military bases for 14 days, which is what experts think is the virus’s incubation period.

Containment: In the early phases of an epidemic, countries often use this strategy of trying to corral and beat back the advance of a virus in hopes of limiting its spread and possibly stamping it out. They restrict movement of people, enact travel bans and quarantine. To use a military analogy, it is treating new cases like a beachhead invasion and surrounding and beating back each new beachhead.

Mitigation: Once it’s clear we are dealing with widespread transmission that will be difficult if not impossible to contain, authorities begin focusing instead on wider preparations, such as getting hospitals ready to handle the influx of patients, stockpiling materials and enacting social distancing policies.

Vaccine: Vaccines are one of the most effective ways to prevent disease. They work by teaching the body’s immune system to recognize and fight specific viruses and bacteria. Unfortunately, that won’t help in the immediate future. Companies are racing to develop vaccines for the new coronavirus in record time. One company, Moderna, hopes to start clinical trial in April and have results ready by July or August. Vaccines may prove critical to preventing a recurrence of coronavirus outbreaks.

Anti-viral medicines: Drugs that fight against other viruses in the body have a better chance of helping with the current outbreak. The drugmaker Gilead Sciences is conducting clinical trials in Wuhan of the antiviral drug remdesivir as a possible treatment for the new coronavirus. The U.S. National Institutes of Health said the drug’s effectiveness will also be studied on some American patients in Nebraska who were returned from overseas. One reason experts are interested and hopeful is that a man hospitalized in Washington state was treated with the antiviral drug and experienced an improvement of his symptoms.