How does coronavirus spread? When will a vaccine be available? Your COVID-19 questions, answered

While COVID-19 has been commonly known as a respiratory illness, many patients experience a wide range of different symptoms that the CDC says can appear anywhere from 2 to 14 days after exposure.

"COVID-19 can look different in different people," it says. "For many people, being sick with COVID-19 would be a little bit like having the flu. People can get a fever, cough, or have a hard time taking deep breaths. Most people who have gotten COVID-19 have not gotten very sick. Only a small group of people who get it have had more serious problems."

According to the CDC, symptoms may include:

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Fatigue
• Muscle or body aches
• Headache
• Loss of taste or smell
• Sore throat
• Congestion or runny nose
• Nausea or vomiting
• Diarrhea

The CDC cautions this list "does not include all possible symptoms," and will continue to be updated as more becomes known about COVID-19.

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"The virus that causes COVID-19 is thought to spread mainly from person to person, mainly through respiratory droplets produced when an infected person coughs, sneezes, or talks," the CDC says. "These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. Spread is more likely when people are in close contact with one another (within about 6 feet)."

A growing number of scientists and public health experts also warn that there is some risk of airborne transmission from tiny respiratory particles that may drift farther than 6 feet, although it is still unclear how much of the spread happens this way. 

The CDC updated its guidelines in October to advise that people who are more than 6 feet away from each other can become infected from small particles that linger in the air, especially in enclosed spaces that have poor ventilation.

Evidence shows most COVID-19 transmission occurs from people who are symptomatic, the World Health Organization (WHO) says. 

Nevertheless, multiple studies have found that people who aren't showing any symptoms can unknowingly spread the virus to others, and a number of "super-spreader events," where many people were infected, have been linked to asymptomatic transmission.

"COVID-19 can be spread by people who do not have symptoms and do not know that they are infected," the CDC says. But WHO notes that more data is needed to better understand transmission.

"WHO is working with countries around the world, and global researchers, to gain better evidence-based understanding of the disease as a whole, including the role of asymptomatic patients in the transmission of the virus," it says. 

The CDC says people can also become infected when they touch a surface with the virus and then touch their mouth, nose or eyes. 

The CDC says it is not yet known when "viral shedding" – the release of the virus from an infected person – begins following infection, or exactly how long it lasts.

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Most known COVID-19 cases are among the adult population. And early research suggests that fewer children than adults who do get the virus end up developing a fever, cough or shortness of breath, according to the American Academy of Pediatrics.

"Few children with COVID-19 have had to be hospitalized," the group says. "However, severe illness has been reported in children, most often in infants less than a year."

Doctors believe there's growing evidence that a rare, mysterious illness appearing in children may be linked to the virus. The illness, commonly known as Multi-System Inflammatory Syndrome in Children (MIS-C), may develop in children some time after they were exposed to the coronavirus.

Symptoms have been compared to those of Kawasaki disease and toxic-shock syndrome, but the illness is being recognized as a "new entity," according to Dr. Luiza Petre, a cardiologist and professor of cardiology at Mount Sinai's School of Medicine in New York.

"What we're seeing is the immune system is actually going into overdrive, impacting the body in a negative way," Dr. Jake Kleinmahon, a pediatric oncologist in New Orleans who has treated several children for the illness, told CBS News in May. "Some of these patients are having inflammation of their coronary arteries, and you can have basically a heart attack."

The American Academy of Pediatrics says children with MIS-C "may become very ill with signs of inflammation in many or all of their internal organs, such as the intestines, heart, lungs, and kidneys." It urges people to contact a pediatrician right away if a child has any of these symptoms:

• Fever lasting more than 3 days
• Abdominal pain, diarrhea or vomiting
• Neck pain
• Rash or changes in skin color
• Bloodshot eyes
• Seems extra tired
• Trouble breathing
• Pain of pressure in the chest that doesn't go away
• Becoming confused
• Unable to wake up or stay awake
• Bluish lips or face

The American Academy of Pediatrics notes that the association between COVID-19 and MIS-C is "not well understood" and wants to "reassure parents that very few children get severely ill from the virus that causes COVID-19."

"In addition, most diagnosed with MIS-C have recovered after getting medical care," it says.

The CDC says pregnant people might be at heightened risk of getting severely ill from COVID-19. "Additionally, there may be an increased risk of adverse pregnancy outcomes, such as preterm birth, among pregnant people with COVID-19," it says. 

"Therefore, if you are pregnant, be mindful about reducing your risk of getting sick. If you are caring for children, you can teach them everyday steps (such as proper handwashing) to help them stay healthy and, in turn, help protect yourself and your family."

A CDC report found that pregnant women accounted for about 9% of lab-confirmed COVID-19 cases in women of childbearing age, even though only about 5% of women of childbearing age are pregnant at any given time.

The report showed that pregnant women had higher rates of hospitalization, of admission to a hospital intensive care unit and of winding up on a breathing machine vs. young women who weren't pregnant. There was no clear evidence of a higher death rate among pregnant women, however.

It's not completely surprising, said Dr. Denise Jamieson, chair of obstetrics and gynecology at the Emory University School of Medicine. Pregnant women have been found to be at higher risk from other infectious respiratory diseases, likely because the lungs decrease in the volume as the uterus grows, Jamieson said.

The CDC urges those who are pregnant to not skip prenatal care appointments but also limit interactions with people as much as possible. It advises keeping a 30-day supply of any needed medicines on-hand and take precautions when interacting with others.  

"Seek care immediately if you have a medical emergency," it says.

-CBS News/The Associated Press

People who are older or have underlying health conditions are at heightened risk of getting severely ill from the virus.

"As you get older, your risk for severe illness from COVID-19 increases. For example, people in their 50s are at higher risk for severe illness than people in their 40s. Similarly, people in their 60s or 70s are, in general, at higher risk for severe illness than people in their 50s," the CDC says.

"The greatest risk for severe illness from COVID-19 is among those aged 85 or older," it says.

But no matter a person's age, the CDC says the following conditions increase a person's risk of severe COVID-19 illness: 

• Chronic kidney disease 
• COPD (chronic obstructive pulmonary disease) 
• Obesity (BMI of 30 or higher) 
• Immunocompromised state (weakened immune system) from solid organ transplant 
• Serious heart conditions, such as heart failure, coronary artery disease, or cardiomyopathies 
• Sickle cell disease 
• Type 2 diabetes 

The CDC also lists these conditions as potentially increasing a person's risk of severe illness, but says more research is needed:

• Asthma (moderate-to-severe) 
• Cerebrovascular disease (affects blood vessels and blood supply to the brain) 
• Cystic fibrosis 
• Hypertension or high blood pressure 
• Immunocompromised state (weakened immune system) from blood or bone marrow transplant, immune deficiencies, HIV, use of corticosteroids, or use of other immune weakening medicines 
• Neurologic conditions, such as dementia 
• Liver disease 
• Pregnancy 
• Pulmonary fibrosis (having damaged or scarred lung tissues) 
• Smoking 
• Thalassemia (a type of blood disorder) 
• Type 1 diabetes 

COVID-19 has also taken a disproportionate toll on Black, Hispanic and Native American communities.

Related:

• CDC expands list of people at high risk of severe illness from COVID-19

It is still unknown whether people who have recovered from COVID-19 are able to get reinfected with the virus. The question hinges on antibodies, and the immunity they may, or may not, provide. 

Studies of other coronaviruses, like SARS and MERS, have shown that people are immune to contracting those viruses for a period of time after their initial infection — but that their immunity is not permanent. 

According to Dr. Lee Riley, chair of the Division of Infectious Disease and Vaccinology at UC Berkeley, people who had SARS have shown to have a few months to about a year of immunity, and people with MERS have shown up to two years of immunity.

Since the virus that causes COVID-19 shares characteristics with those viruses, scientists are looking at them for guidance, but not definitive answers. As a new virus, only time will tell what kind of immunity people have to it.

Dr. Theresa Madaline, a healthcare epidemiologist and assistant professor of infectious diseases at the Albert Einstein College of Medicine in New York, said a study in South Korea showed that people who had previously been infected with coronavirus had positive nasal swabs weeks after having the virus, but it's unclear whether those positive results were from new active virus, or "dead remnants from the original virus."

There's still a lot that we don't know about the coronavirus, including the weight that should be given to positive antibody tests. Dr. Madaline stressed that people who test positive for antibodies should continue to wear masks, wash hands frequently, and social distance.

"It's not a passport for them to move around freely," she said.

Cloth face coverings help prevent an infected person from spreading the coronavirus to others by helping to keep respiratory droplets contained, the CDC says. It recommends that people older than the age of 2 wear face coverings in public "as a simple barrier."

Coverings like masks help prevent respiratory droplets from dispersing into the air when someone talks or raises their voice, or coughs or sneezes. They are "most likely" to reduce COVID-19's spread when people in public widely use them.

Dr. Anthony Fauci, the nation's top infectious disease official, told CBS News in a recent interview, "The best way to protect yourself and to prevent acquisition of and spread of infection is to avoid crowds. Avoid crowds. If in fact, for one reason or other, you feel compelled to do that, which we don't recommend, then wear a mask at all times."

Surgeon General Jerome Adams urged Americans "Please, please, wear a face covering when you go out in public. It is not an inconvenience. It is not a suppression of your freedom. It actually is a vehicle to achieve our goals, it adds to your convenience and your freedom. … When you do not wear your face covering, we see higher spread and have to close places."

The CDC notes that COVID-19 can be spread by people who do not have symptoms and don't know that they are infected: "That's why it's important for everyone to wear cloth face coverings in public settings and practice social distancing (staying at least 6 feet away from other people)."

About a dozen different vaccines are in various stages of testing worldwide, including in Britain, China and the United States. 

In December, Pfizer and Moderna became the first two companies to receive emergency use authorization from the FDA for their vaccines and begin distributing them in the U.S. The companies say clinical trials show their vaccines are safe and have an efficacy rate of about 95%.

The Pfizer and Moderna vaccines each require two doses several weeks apart. Plans for an ambitious nationwide vaccination program are ramping up, with frontline health care workers among the first in line, along with nursing home residents and other high-risk groups.

Health officials have said most Americans who want the vaccine should be able to get it by the second quarter of 2021.

-CBS/AP

Health experts say there's a lower chance of getting the virus outdoors than gathering inside. But sunbathing and swimming in the ocean with other people is not risk-free. 

"Even though staying outdoors is safest, we know that a crowded beach can put you at much higher risk of COVID infection," Dr. Shoshana Ungerleider, an internal medicine physician, said on CBSN.

She said it's important to keep your distance from other people on land and in the water and that if it gets too crowded, "it's important to leave the area."  

"I like to say at least 10 feet away from others just to give yourself a buffer, and don't swim up next to other people where they could cough or spit or their breath could get on you," she said.

Ungerleider recommended going with a small group "that you know and that you trust."

"The larger the group, the greater your risk," she said.    

Ungerleider recommended bringing two face masks in case one gets wet and suggested bringing your own chairs and toys, as well as disinfectant wipes and hand sanitizer.

"Consider that everything that you touch could be contaminated," she said. 

The CDC warns that any "travel increases your chances of getting and spreading COVID-19."

Henry Harteveldt, a travel industry analyst at the Atmosphere Research Group, says flying is a safe option for travelers, "but it is not a risk-free option."

According to Harteveldt, airports have taken steps to protect travelers like cleaning with greater frequency, installing plexiglass shields at check-in counters and hand sanitizing stations throughout the building. 

But unlike airports, which tend to follow local regulations, safety precautions vary once you're on a plane, he said. Some airlines have temporarily stopped filling middle seats to increase distance between passengers. Passengers must wear masks on flights, and some food and beverage service is being curtailed.

But American Airlines recently announced that it will begin booking flights to capacity on July 1 instead of leaving vacant seats for social distancing.

CDC Director Dr. Robert Redfield told a Senate committee hearing there was "substantial disappointment" with American Airlines' decision to fill planes. "We don't think it's the right message," he said, adding that it is under "critical review" by the CDC.

Harteveldt urged travelers to familiarize themselves with an airline's COVID-19 precautions before booking a flight. He recommends passengers pack: 

• Multiple face coverings, especially for long flights, as they may not be provided to you.

• Hand sanitizer for every person traveling with you. TSA is now allowing passengers to bring 12 oz. hand sanitizers, as opposed to the previous 3 oz.

• Disposable gloves and sanitizing wipes. Even if the airline is cleaning planes between flights, wiping down your seat, tray table, and window shade can eliminate germs.

• Your own food. Most airlines are not selling food on domestic flights, and many airport restaurants are closed.

Before you get to the airport, Harteveldt said travelers should also download their airline's app and check in ahead of time to reduce contact with other people. And, to further avoid passing germs, hold onto your phone when TSA scans your boarding pass.

If you can avoid checking your bag, do so, he said. And whether or not you've checked a bag, wipe it down before you leave the airport. 

"You can't be too careful," he said.

The CDC recommends that before getting on a plane, travelers first scrutinize their destination. If COVID-19 is spreading where you are going — which you can determine on the CDC's COVID tracker map — the agency warns travelers that they could become infected while away from home. 

Harteveldt echoed that advice, saying that travelers should be most concerned about the status of cases and available hospital beds in the place they are headed. Special consideration should be taken if you are traveling to states like Texas, Arizona, Florida, or California where cases are on the rise. 

The same scrutiny should be given to where you are leaving from. The CDC urges travelers to ask themselves if COVID-19 is spreading in their community before departing. "Even if you don't have symptoms, you can spread COVID-19 to others while traveling," reads its website. 

Dr. Theresa Madaline, a healthcare epidemiologist and assistant professor of infectious diseases at the Albert Einstein College of Medicine in New York, said she would not travel right now "given the amount of COVID activity in the country." 

"I personally will not be flying on an airplane anytime soon," she said.

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Whether or not it is safe to go to the gym during the coronavirus pandemic depends on where you live and the precautions you and the gym take.

If cases of COVID-19 are poorly controlled where you live, experts say it's best to stay away. But if you live in an area where the spread is being contained, there are ways to minimize risk when going for a workout.

To ensure everyone stays at least 6 feet apart, gyms should take steps such as moving machines, blocking off areas and limiting the number of people allowed inside, said Dr. Marybeth Sexton, an assistant professor of infectious diseases at Emory University.

Avoiding the locker room, bringing your own water bottle and using hand sanitizer also helps reduce risk, Sexton says.

The U.S. Centers for Disease Control and Prevention also suggests checking in online, rather than in person, and seeking activities that are outdoors instead of indoors when possible.

Gym staff should be cleaning exercise machines between uses and regularly wiping down other frequently touched areas with products that kill viruses. And experts said face coverings should be worn at the gym whenever possible.

Sexton also suggested bringing a backup mask. If the one you're wearing gets really damp with sweat, she said it might not be as effective.

Even for those being careful, gyms pose a risk. Many are indoors, where ventilation is limited and social distancing can be challenging. In an ongoing pandemic, if you can manage to break a sweat without returning to the gym just yet, that's the best option, according to Sexton.

"If you can exercise by yourself outside, that's safer than being at the gym," she said. 

The CDC says "it may be possible" for someone to get COVID-19 by touching a surface containing the coronavirus and then touching their eyes, nose or mouth. But it says that isn't the main way the virus spreads.

Outside of the body the virus weakens and dies over time, although studies suggest it is able to survive on surfaces for periods ranging from hours to days. The length of time depends on the temperature and the type of surface, as well as other factors. 

"For instance, a small amount of the new coronavirus is still detectable on plastic surfaces for up to three days, on stainless steel for up to two days and up to one day on cardboard, but it's at less than 0.1% of the starting virus material," explains Johns Hopkins Medicine.

"So far, evidence suggests that the virus does not survive as well on a soft surface (such as fabric) as it does on frequently touched hard surfaces like elevator buttons and door handles."

As Johns Hopkins Medicine notes, evidence suggests the coronavirus doesn't survive as well on fabric and other soft surfaces as it does on "frequently touched hard surfaces" like door handles and elevator buttons.

The CDC doesn't say you need to wash your clothes when returning from routine errands like grocery shopping. 

But it does have recommendations when it comes to handling the clothing of someone who is sick, including not shaking that person's dirty laundry. "This will minimize the possibility of dispersing virus through the air," the CDC says. 

It says dirty laundry from a sick person can be washed with other people's clothing. "If possible, launder items using the warmest appropriate water setting for the items and dry items completely."

It also recommends disinfecting hampers and considering using bag liners that can be washed or thrown away.

Health professionals caring for COVID-19 patients should also take protective measures. According to an article in Family Practice Management, the American Academy of Family Physicians' peer-reviewed journal, they should shower and change into clean clothing and shoes before going home, or change in an isolated location at home if that's not possible, such as a mudroom.

"Put dirty clothes and shoes into a bag for soiled clothing. Consider using a cloth bag you can wash along with your dirty clothes each day," it says. 

It also says clothing worn at work can be washed at home using typical laundry detergent.