Editor's note: For the latest updates on the 2021 coronavirus outbreak, see our news coverage.
What Is COVID-19?
COVID-19 is a disease caused by SARS-CoV-2 that can trigger what doctors call a respiratory tract infection. It can affect your upper respiratory tract (sinuses, nose, and throat) or lower respiratory tract (windpipe and lungs).
It spreads the same way other coronaviruses do, mainly through person-to-person contact. Infections range from mild to deadly.
SARS-CoV-2 is one of seven types of coronavirus, including the ones that cause severe diseases like Middle East respiratory syndrome (MERS) and sudden acute respiratory syndrome (SARS). The other coronaviruses cause most of the colds that affect us during the year but aren't a serious threat for otherwise healthy people.
Is there more than one strain of SARS-CoV-2?
An early Chinese study of 103 COVID-19 cases found two strains, which they named L and S. The S type is older, but the L type was more common in early stages of the outbreak. They think one may cause more cases of the disease than the other, but they're still working on what it all means.
It is also normal for a virus to change, or mutate, as it infects people and this virus has done so. There are several variants that are now spreading, some proving to be more contagious as well as more deadly than the original virus.
Throughout the pandemic, scientists have kept a close eye on variants like:
How long will the coronavirus last?
There's no way to tell how long the pandemic will continue. There are many factors, including the public's efforts to slow the spread, researchers' work to learn more about the virus, their search for a treatment, and the success of the vaccines.
Symptoms of COVID-19
The main symptoms include:
- Shortness of breath
- Trouble breathing
- Chills, sometimes with shaking
- Body aches
- Sore throat
- Congestion/runny nose
- Loss of smell or taste
The virus can lead to pneumonia, respiratory failure, heart problems, liver problems, septic shock, and death. Many COVID-19 complications may be caused by a condition known as cytokine release syndrome or a cytokine storm. This is when an infection triggers your immune system to flood your bloodstream with inflammatory proteins called cytokines. They can kill tissue and damage your organs. In some cases, lung transplants have been needed.
If you notice the following severe symptoms in yourself or a loved one, get medical help right away:
- Trouble breathing or shortness of breath
- Ongoing chest pain or pressure
- Can't wake up fully
- Bluish lips or face
Strokes have also been reported in some people who have COVID-19. Remember FAST:
- Face. Is one side of the person's face numb or drooping? Is their smile lopsided?
- Arms. Is one arm weak or numb? If they try to raise both arms, does one arm sag?
- Speech. Can they speak clearly? Ask them to repeat a sentence.
- Time. Every minute counts when someone shows signs of a stroke. Call 911 right away.
If you're infected, symptoms can show up in as few as 2 days or as many as 14. It varies from person to person.
According to researchers in China, these were the most common symptoms among people who had COVID-19:
- Fever 99%
- Fatigue 70%
- Cough 59%
- Lack of appetite 40%
- Body aches 35%
- Shortness of breath 31%
- Mucus/phlegm 27%
Some people who are hospitalized for COVID-19 also have dangerous blood clots, including in their legs, lungs, and arteries.
What to do if you think you have it
If you live in or have traveled to an area where COVID-19 is spreading:
- If you don't feel well, stay home. Even if you have mild symptoms like a headache and runny nose, stay in until you're better. This lets doctors focus on people who are more seriously ill and protects health care workers and people you might meet along the way. You might hear this called self-quarantine. Try to stay in a separate room away from other people in your home. Use a separate bathroom if you can.
- Call the doctor if you have trouble breathing. You need to get medical help as soon as possible. Calling ahead (rather than showing up) will let the doctor direct you to the proper place, which may not be your doctor's office. If you don't have a regular doctor, call your local board of health. They can tell you where to go for testing and treatment.
- Follow your doctor's advice and keep up with the news on COVID-19. Between your doctor and health care authorities, you'll get the care you need and information on how to prevent the virus from spreading.
For more information about COVID-19, see our FAQ.
How do I know if it's COVID-19, a cold, or the flu?
Symptoms of COVID-19 can be similar to a bad cold or the flu. Your doctor will suspect COVID-19 if:
- You have a fever and a cough.
- You have been exposed to people who have it within the last 14 days.
Cold vs. Flu vs.
Allergies vs. COVID-19
(can range from moderate to severe)
High (100-102 F), Can last 3-4 days
Can be present
General aches, pains
Usual, often severe
Can be present
Intense, starts early, c
Usual gone in 2-3 weeks
Can be present
Has been reported
Has been reported
Has been reported
Mild to moderate
Common, can become severe
Loss of smell and taste
Has been reported
|Pink Eye||Can Happen||Can Happen||Can Happen||Can Happen|
Sometimes in children
Has been reported
|Shortness of Breath||Rare||Rare||Rare, except for those with allergic asthma||In more serious infections|
|Chest Pain||Rare||In more serious infections||Rare||In more serious infections|
Is COVID-19 worse than the flu?
Unlike the flu, a lot of people aren't immune to the coronavirus because it's so new. If you do catch it, the virus triggers your body to make things called antibodies. Researchers are looking at whether the antibodies give you protection against catching it again.
The coronavirus also appears to cause higher rates of severe illness and death than the flu. But the symptoms themselves can vary widely from person to person.
Is COVID-19 seasonal like the flu?
While scientists hoped initially that higher temperatures and humidity levels might help slow the spread of the coronavirus, that was not the case. Experts advise caution and say thorough public health efforts have more influence than weather on the spread. Also, past flu pandemics have happened year-round.
Causes of the New Coronavirus
Researchers aren't sure what caused it, and investigations as to its origin are ongoing. There's more than one type of coronavirus. They're common in people and in animals including bats, camels, cats, and cattle. SARS-CoV-2, the virus that causes COVID-19, is similar to MERS and SARS. They all came from bats.
Coronavirus Risk Factors
Anyone can get COVID-19, and most infections are mild. The older you are, the higher your risk of severe illness.
You also a have higher chance of serious illness if you have one of these health conditions:
- Chronic kidney disease
- Chronic obstructive pulmonary disease (COPD)
- A weakened immune system because of an organ transplant
- Serious heart conditions such as heart failure or coronary artery disease
- Sickle cell disease
- Type 2 diabetes
Conditions that could lead to severe COVID-19 illness include:
- Moderate to severe asthma
- Diseases that affect your blood vessels and blood flow to your brain
- Cystic fibrosis
- High blood pressure
- A weakened immune system because of a blood or bone marrow transplant, HIV, or medications like corticosteroids
- Liver disease
- Damaged or scarred lung tissue (pulmonary fibrosis)
- Type 1 diabetes
Some children and teens who are in the hospital with COVID-19 have an inflammatory condition that doctors are calling multisystem inflammatory syndrome in children. Doctors think it may be linked to the virus. It causes symptoms similar to those of toxic shock and of Kawasaki disease, a condition that causes inflammation in kids' blood vessels.
How Are Mood Disorders Linked to Severe COVID-19?
One large study reviewed 91 million people with mood disorders and other mental health conditions. It found that if you have preexisting mood disorders, you're at a high risk for hospitalization or death but not necessarily severe COVID-19.
According to the study, there are several socio-economic reasons why preexisting mood disorders can increase your chances for hospitalization and death if you get COVID-19.
- Lack of access to preventative health care
- Ability to understand health recommendations
- Lack of access to affordable health care
- Living in tight spaces or facilities like nursing homes, homeless shelters, prisons, or psychiatric inpatient units
In addition, people living with mental health conditions may have certain mood disorder symptoms that can interfere with our ability to care for ourselves and be engaged in our health. This can make it hard to effectively follow health behaviors like maintaining social distance or staying in quarantine to reduce the spread of the infection.
Moreover, people with mental health and mood disorders are also more likely to have conditions like diabetes and heart problems that are major risk factors for severe COVID-19.
Another study looked at 7,348 people with preexisting mood and psychiatric conditions with confirmed COVID-19 infections. It found those living with schizophrenia were more than twice as likely to die from COVID-19. Study experts noted that possible delay in access to health care and other unknown or monitored health risk factors may have led to the higher death rate.
How does the coronavirus spread?
SARS-CoV-2, the virus, mainly spreads from person to person. People release respiratory fluids during exhalation (e.g., quiet breathing, speaking, singing, exercise, coughing, sneezing) in the form of droplets across a spectrum of sizes.These droplets carry virus and transmit infection. The largest droplets settle out of the air rapidly, within seconds to minutes. The smallest very fine droplets, and aerosol particles formed when these fine droplets rapidly dry, are small enough that they can remain suspended in the air for minutes to hours.
Risk of transmission is greatest within three to six feet of an infectious source where the concentration of these very fine droplets and particles is greatest. If you breathe them in or swallow them, the virus can get into your body. Some people who have the virus don't have symptoms, but they can still spread the virus.
While less likely, you can also get the virus from touching a surface or object the virus is on, then touching your mouth, nose, or possibly your eyes. Most viruses can live for several hours on a surface that they land on. A study shows that SARS-CoV-2 can last for several hours on various types of surfaces:
- Copper (pennies, teakettles, cookware): 4 hours
- Cardboard (shipping boxes): up to 24 hours
- Plastic (milk containers, detergent bottles, subway and bus seats, elevator buttons):2 to 3 days
- Stainless steel (refrigerators, pots and pans, sinks, some water bottles): 2 to 3 days
That's why it's important to wash or sanitize your hands regularly and disinfect surfaces to get rid of the virus.
Some dogs and cats have tested positive for the virus. A few have shown signs of illness. There's no evidence that humans can catch this coronavirus from an animal, but it appears it can be passed from humans to animals.
What is community spread?
Doctors and health officials use this term when they don't know the source of the infection. With COVID-19, it usually refers to someone who gets the virus even though they haven't been out of the country or haven't been exposed to someone who's traveled abroad or who has COVID-19.
In February 2020, the CDC confirmed a COVID-19 infection in California in a person who had not traveled to an affected area or been exposed to someone with the disease. This marked the first instance of community spread in the U.S. It's likely that person was exposed to someone who was infected but didn't know it. This type of occurrence has been happening with the variants as well.
How fast is it spreading?
The number of people infected by SARS-CoV-2 changes every day. See our news story for the latest updates on this developing story.
How contagious is the coronavirus?
The transmission rate is relatively high. Early research has estimated that one person who has it can spread it to between 2 and 3.5 others. One study found that the rate was higher, with one case spreading to between 4.7 and 6.6 other people. By comparison, one person who has the seasonal flu will pass it to between 1.1 and 2.3 others.
The Omicron variant, which is now the dominant strain of COVID-19 in the United States, is highly contagious and will likely spread faster than the original virus. Scientists are still looking into how easily Omicron spreads compared to the previous dominant variant, Delta. The CDC expects that someone who's infected with Omicron can spread it to other people, even if the infected person is vaccinated or doesn't have symptoms.
The CDC reports there is evidence COVID-19 can be transmitted if you get within 6 feet of someone who is infectious for a total of 15 minutes throughout a day. It had previously been believed the exposure had to be 15 minutes at a time.
We can work to lower the transmission rate by wearing cloth face masks when we can't stay 6 feet away from others, washing hands often, keeping common surfaces clean, limiting contact with other people, and getting vaccinated.
Can coronavirus be transmitted through groceries, packages, or food?
You're much more likely to get COVID-19 from another person than from packages, groceries, or food. If you're in a high-risk group, stay home and use a delivery service or have a friend shop for you. Have them leave the items outside your front door, if you can. If you do your own shopping, wear a cloth face mask and try to stay at least 6 feet away from other shoppers.
Wash your hands for at least 20 seconds before and after bringing things into your home. The coronavirus can linger on hard surfaces, so clean and disinfect countertops and anything else your bags have touched. You can wipe down plastic, metal, or glass packaging with soap and water if you want.
There's no evidence that anyone has gotten COVID-19 from food or food containers.
Call your doctor or local health department if you think you've been exposed and have symptoms like:
- Fever of 100 F or higher
- Trouble breathing
Testing facilities readily available in most areas. While some require an appointment, others are simply drive-up. Home testing kits are also widely available.
A swab test is the most common testing method. It looks for signs of the virus in your upper respiratory tract. You or the person giving the test puts a swab up your nose to get a sample from the back of your nose and throat. That sample usually goes to a lab that looks for viral material, but some areas may have rapid tests that give results in as little as 15 minutes.
If there are signs of the virus, the test is positive. A negative test could mean there is no virus or there wasn't enough to measure. That can happen early in an infection. It usually takes 24 hours to get results, but the tests must be collected, stored, shipped to a lab, and processed.
The FDA granted emergency-use authorizations for tests that include home nasal swab tests, which you collect yourself and express ship back to the lab for analysis. The agency also approved several at-home rapid tests. You can buy these over the counter in pharmacies, at retail stores, or online -- but kits that give you rapid results (within minutes) can sometimes be hard to find due to high demand. At-home tests are also available for free at some local health departments or federally qualified health centers.
A swab test can only tell whether you have the virus in your body at that moment. But you may also consider taking an antibody test which can show whether you've ever been exposed to the virus, even if you didn't have symptoms. This is important in officials' efforts to learn how widespread COVID-19 is. In time, it might also help them figure out who's immune to the virus.
The FDA is working with laboratories across the country to develop more tests.
Getting vaccinated against COVID-19 is a key part of prevention. But you should also take these steps:
- Cover your nose and mouth in public. If you have COVID-19, you can spread it even if you don't feel sick. Wear a mask to protect others. This isn't a replacement for social distancing. You still need to keep a 6-foot distance between yourself and those around you. Don't use a face mask meant for health care workers. And don't put a face covering on anyone who is:
- Under 2 years old
- Having trouble breathing
- Unconscious or can't remove the mask on their own for other reasons
- Wash your hands often with soap and water or clean them with an alcohol-based sanitizer. This kills viruses on your hands.
- Don't touch your face. Coronaviruses can live on surfaces you touch for several hours. If they get on your hands and you touch your eyes, nose, or mouth, they can get into your body.
- Practice social distancing. Because you can have and spread the virus without knowing it, you should stay home as much as possible. If you do have to go out, stay at least 6 feet away from others.
- Clean and disinfect. You can clean first with soap and water, but disinfect surfaces you touch often, like tables, doorknobs, light switches, toilets, faucets, and sinks. Use a mix of household bleach and water (1/3 cup bleach per gallon of water, or 4 teaspoons bleach per quart of water) or a household cleaner that's approved to treat SARS-CoV-2. You can check the Environmental Protection Agency (EPA) website to see if yours made the list. Wear gloves when you clean and throw them away when you're done.
There's no proof that herbal therapies and teas can prevent infection.
COVID-19 preparation tips
In addition to practicing the prevention tips listed above, you can:
- Meet as a household or larger family to talk about who needs what.
- If you have people at a higher risk, ask their doctor what to do.
- Talk to your neighbors about emergency planning. Join your neighborhood chat group or website to stay in touch.
- Find community aid organizations that can help with health care, food delivery, and other supplies.
- Make an emergency contact list. Include family, friends, neighbors, carpool drivers, doctors, teachers, employers, and the local health department.
- Choose a room (or rooms) where you can keep someone who's sick or who's been exposed separate from the rest of you.
- Talk to your child's school about keeping up with assignments.
- Set yourself up to work from home if your office is closed.
- Reach out to friends or family if you live alone. Make plans for them to check on you by phone, email, or video chat.
Can a face mask protect you from infection?
A mask is an added layer of protection for everyone, on top of vaccines and social distancing efforts. You can spread the virus when you talk or cough, even if you don't know that you have it or if you aren't showing signs of infection.
It's important to wear a mask in a variety of situations:
If you're fully vaccinated, wear a mask indoors in public places if you're in an area where there's a high or “substantial” amount of COVID spreading around. If you aren't fully vaccinated, always wear a mask in indoor public places. That goes for people 2 years old and up.
If you have a chronic health condition or you're taking meds that weaken your immune system, wear a mask in indoor public places even if you're fully vaccinated. Do this unless your doctor tells you otherwise. In general, you don't need to wear a mask outside, where it's harder for the coronavirus to spread. But if COVID-19 cases are high in your area, consider wearing one in crowded outdoor places and for outdoor get-togethers that involve close contact with people who aren't fully vaccinated.
Anyone should wear a face mask if they're sick and around other people or animals, even at home. Caregivers should use them when cleaning and disinfecting a sick person's bedroom or bathroom. If you need to call 911, put on a mask before medical help arrives.
Some people shouldn't wear masks:
- Kids under 2 years old
- Someone with a disability who can't wear a mask or can't safely wear one to the disability
- A person who has a job in which wearing a mask would create a risk to co-workers' health or safety as determined by the workplace risk assessment
What are the different types of face masks?
You have several options:
Cloth masks are washable and reusable. The best ones have multiple layers of breathable fabric and fit snugly over your nose and mouth. It's a good idea to buy ones that come with a nose wire and are made with fabric that can block light.
Disposable masks, also called surgical masks, are also widely available. Choose ones that have several layers of non-woven material. Pick a size that fits properly over your nose and mouth and comes with a nose wire. Don't wear one that has gaps around the sides of your face or nose, or has wet or dirty material.
N95 respirator masks fit tightly around your face and filter out 95% or more of the smallest particles in the air. They have to fit you just right in order to work.
It's fine to buy a basic, disposable N95 respirator. Choose one that's high quality and says “NIOSH Approved” on the label.
Health care workers need priority access to a type of N95 respirator that's specially labeled “surgical.” Supplies of these can be limited and demand for them can be high.
Is it safe to travel during a pandemic?
Crowded places can raise your chances of getting COVID-19. The CDC recommends against international or cruise ship travel during the pandemic. Restrictions are being eased for those who are vaccinated, and some areas are using “vaccine passports” as a way to open up to vaccinated travelers.
A few questions may help you decide whether it's safe to travel:
- Is the coronavirus spreading where you're going?
- Will you have close contact with other people during the trip?
- Are you at higher risk of severe illness if you catch the virus?
- Do you live with someone who has a serious medical condition?
- Will the place where you'll be staying be cleaned?
- Will you have access to food and other necessities?
If you choose to travel, stay away from sick people. Wash your hands often, and try not to touch your face. Wear a cloth face mask when you are around other people. All airlines require all customers to use them. They are also required on other forms of public transportation such as trains and buses.
How can you help stop the spread of the coronavirus?
Because the virus spreads from person to person, it's important to limit your contact with other people as much as possible. and avoid large gatherings. Many states and cities have eased restrictions but this doesn't mean the virus is gone. Continue to follow safety practices such as wearing a cloth face mask in public places and washing your hands.
While many companies continue to use work-from-home practices, that is not possible for a lot of workers. Some people work in “essential businesses” that are vital to daily life, such as health care, law enforcement, and public utilities. Everyone else should continue to limit your time in public as much as you can and wear a cloth face mask when you can't.
The following terms have now become commonplace:
- Social distancing or physical distancing, keeping space between yourself and other people when you have to go out
- Quarantine, keeping someone home and separated from other people if they might have been exposed to the virus
- Isolation, keeping sick people away from healthy people, including using a separate “sick” bedroom and bathroom when possible
Precautions should still be followed even if you are vaccinated.
Vaccines are now available for children as young as 5 years old. These vaccines are a third the dose of the Pfizer-BioNTech COVID-19 vaccine, which is authorized in those 12 and older. As in the adult version, the children's version requires two does, take 3 weeks apart.
A two-dose Moderna vaccine is also approved for adults, as is a single dose Johnson & Johnson vaccine.
Top health experts have a preference for the type of vaccine that you choose. They recommend that you choose a vaccine made with mRNA (like the ones from Pfizer and Moderna) rather than the J&J vaccine, which is made differently. The recommendation is endorsed by the CDC and comes from the Advisory Committee on Immunization Practices, which reviewed the latest evidence on the effectiveness, safety, and rare side effects of the available vaccines.
That said, if you can't get an mRNA vaccine or you don't want to, you should definitely get the J&J vaccine. Receiving any COVID-19 vaccine is better than being unvaccinated, experts say.
Booster shots of the Pfizer and Moderna vaccines are recommended for everyone 18 years and older at least 6 months after you've gotten your first two doses. (Sixteen- and 17-year-olds who got their initial two doses from Pfizer are eligible to get the Pfizer booster, too.)
A J&J booster is recommended for those 18 years and older at least 2 months after receiving their original dose of the J&J vaccine.
If you're 18 or older, you can get a booster dose of any of the COVID vaccines authorized in the U.S. That means you don't have to stick with same the vaccine you initially got. For example, if your initial doses came from Moderna, you can get a booster dose from Pfizer.
But remember, teens 16 and 17 who got the Pfizer vaccine are allowed only to get a Pfizer booster shot.
COVID-19 vaccines were developed at an unprecedented speed, with testing in humans starting in March 2020. The FDA says that no corners were cut to allow for approval and that the inoculations are safe. The CDC has said it is safe for pregnant women and there's no evidence that antibodies formed from COVID-19 vaccination cause any problem with pregnancy.
There's no specific treatment for COVID-19. People who get a mild case need care to ease their symptoms, like rest, fluids, and fever control. Take over-the-counter medicine for a sore throat, body aches, and fever. But don't give aspirin to children or teens younger than 19.
You might have heard that you shouldn't take ibuprofen to treat COVID-19 symptoms. But the National Institutes of Health says people who have the virus can use nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen as usual.
Antibiotics won't help because they treat bacteria, not viruses. If you hear about people with COVID-19 getting antibiotics, it's for an infection that came along with the disease.
People with severe symptoms need to be cared for in the hospital.
The antiviral medication called remdesivir (Veklury) is the first medication to get FDA approval for treatment of patients hospitalized with COVID-19. Originally developed to treat Ebola, evidence shows that those treated with remdesivir recovered in about 11 days compared to 15 days for those treated with a placebo.
Many clinical trials are under way to explore treatments used for other conditions that could fight COVID-19 and to develop new ones.
For instance, trials are under way for tocilizumab, another medication used to treat autoimmune conditions. And the FDA is also allowing clinical trials and hospital use of blood plasma from people who've had COVID-19 and recovered to help others build immunity. You'll hear this called convalescent plasma. Currently, evidence of its effectiveness is limited.
Early in the pandemic, the antimalarial drugs hydroxychloroquine and chloroquine were considered as possible treatments. The FDA later rescinded an emergency use order because studies found that the drugs were ineffective and the risks outweighed the benefits.
A variety of steroid medications are being used including dexamethasone which is used to treat conditions such as arthritis, blood/hormone/immune system disorders, allergic reactions,. More studies on effectiveness are still being conducted.
Is there a cure for the coronavirus?
There's no cure yet, but researchers are working hard to find one.
Every case is different. You may have mild flu-like symptoms for a few days after exposure, then get better. But some cases can be severe or fatal.
Symptoms can also linger for weeks, even if they're mild.
More than a third of people older than 18 who have signs of the virus aren't totally recovered 2 or 3 weeks later, according to a CDC survey. Fatigue and cough were the symptoms that were most likely to linger.
Some other people who've had COVID-19 develop a condition similar to myalgic encephalomyelitis, also known as chronic fatigue syndrome. They may have a brain fog, severe fatigue, pain, trouble thinking, or dizziness.
What is the recovery rate for coronavirus?
Scientists and researchers are constantly tracking COVID-19 infections and recoveries. But they don't have information about the outcome of every infection. Early estimates predict that the overall COVID-19 recovery rate will be between 97% and 99.75%.
Yes. There have been cases of reinfection reported, but the CDC says they're rare.
Still, early data suggests that the Omicron variant is more likely to reinfect someone than the Delta variant. And one study suggests that you can get reinfected with COVID in 3 months or less if you're unvaccinated. The researchers who did the study think reinfections will become more and more common as immunity wears off and new variants emerge.
With other coronaviruses that only cause colds, you have a period that you're immune, but that goes away over time. That also appears to be the case with this coronavirus. Immunity is estimated to last at least three to four months.
Are coronaviruses new?
Coronaviruses were first identified in the 1960s. Almost everyone gets a coronavirus infection at least once in their life, most likely as a young child. In the United States, regular coronaviruses are more common in the fall and winter, but anyone can come down with a coronavirus infection at any time.
The symptoms of most coronaviruses are similar to any other upper respiratory infection, including a runny nose, coughing, sore throat, and sometimes a fever. In most cases, you won't know whether you have a coronavirus or a different cold-causing virus, such as a rhinovirus. You treat this kind of coronavirus infection the same way you treat a cold.
Have there been other serious coronavirus outbreaks?
Coronaviruses have led to two serious outbreaks:
- Middle East respiratory syndrome (MERS). About 858 people have died from MERS, which first appeared in Saudi Arabia and then in other countries in the Middle East, Africa, Asia, and Europe. In April 2014, the first American was hospitalized for MERS in Indiana, and another case was reported in Florida. Both had just returned from Saudi Arabia. In May 2015, there was an outbreak of MERS in South Korea, which was the largest outbreak outside of the Arabian Peninsula.
- Severe acute respiratory syndrome (SARS). In 2003, 774 people died from an outbreak. As of 2015, there were no further reports of cases of SARS.