New information about how COVID-19 behaves is constantly emerging, so we are learning more about how the virus spreads every day. According to the Centers for Disease Control and Prevention, it is mainly transmitted by respiratory droplets from person to person in close proximity via talking, coughing, or sneezing. Knowing when you are contagious can greatly reduce the risk of transmission to others.

Even if you do not have or show any symptoms of the disease, such as fever, fatigue, or shortness of breath, you can still spread COVID-19, according to the agency. However, while it is most likely transmitted when people are in close proximity, the CDC acknowledges that the infectious virus can linger on in the air or on surfaces, meaning it can be inhaled even if an infected person has left the area. Less commonly, a person can become ill by touching a contaminated surface and then touching their mouth, nose, or eyes.

According to Harvard Health Publishing, if you come into contact with the virus, it takes from two to 14 days from the time you were exposed to COVID-19 to the time you develop symptoms. During this incubation period, you can still transmit the virus to others, say experts, and people are thought to be the most contagious 48 to 72 hours before they start showing symptoms, which is why public health officials urge everyone to wear face masks and stay away from others.

The Harvard experts warn that some people do not develop any symptoms at all, and may be even more likely to spread the illness because they are not aware they have COVID-19. Researcher Daniel Oran co-authored a study on the prevalence of asymptomatic SARS-CoV-2 infection and found that 32% of cases in England and 33% in Spain were asymptomatic.

By the 10th day after COVID-19 symptoms subside, people are thought to be no longer contagious, according to Harvard Health Publishing. Even those who are asymptomatic but test positive for the virus should not be infectious after this time, although there have been rare cases to contradict this.

“A full 14-day quarantine remains the best way to avoid spreading the virus to others after you’ve been exposed to someone with COVID-19,” write the Harvard experts, acknowledging that the CDC guidelines now say you can end your quarantine after 10 days if you don’t have any symptoms, or after seven days if you have a negative COVID-19 test two days before you plan to finish quarantine.

The CDC also suggests that even if you have tested negative for COVID-19, you should quarantine if you have an encounter with someone who has the virus. “By self-quarantining for 14 days, you lower the chance of possibly exposing others to COVID-19,” says the agency.

Those who have been exposed to COVID-19 or tested positive should also be very careful to reduce the risk of transmission to family members.

Home may be where the heart is, but it is also the most likely place to spread COVID-19. The CDC released a report that found “household transmission of SARS-CoV-2 is common and occurs early after illness onset.” The CDC warned that people should “isolate immediately at the onset of COVID-like symptoms as a result of high-risk exposure, or at a time of a positive test result, whichever comes first.” The CDC added that all members of the household should wear masks within shared spaces of the infected individual.

According to Eat This, Not That!, the CDC researchers found it took less than a week for one family member to transmit the virus to another no matter if that individual was a child or an adult. According to CNN, the study, published in a recent CDC Morbidity and Mortality Weekly Report, suggested that family members who believe they are infected should stay in a separate bedroom and use their own bathroom if possible.

The researchers noted that 53% of people who lived with someone with COVID-19 became infected, and 75% of these secondary infections occurred within a week, according to CNN.

Here are tips on how to safely quarantine your home if someone develops COVID-19.

If you have already had COVID-19, new data from a study of 11,000 healthcare workers in the U.K. found that people who have been infected with COVID-19 may have immunity from symptomatic infection for at least six months.

According to the Daily Mail, the researchers said: “We conclude that SARS-CoV-2 infection appears to result in protection against symptomatic infection in working age adults, at least in the short term.”

A previous U.S. study from the Icahn School of Medicine at Mount Sinai found that 90% of people who recover from COVID-19 have immunity for at least five months. Professor Florian Krammer, a virologist at Icahn who lead the study team, said in a statement that “more than 90% of people who were mildly or moderately ill produce an antibody response strong enough to neutralize the virus, and the response is maintained for several months,” according to CNN.