Coronavirus Resource Center

As coronavirus spreads, many questions and some answers

The rapid spread of the virus that causes COVID-19 continues to spark alarm worldwide. Countries around the world are grappling with surges in confirmed cases, hospitalizations, and deaths. Calls for preventive measures such as social distancing and face coverings to slow the spread of coronavirus have created a new normal in many places. Health care workers and hospitals have ramped up capabilities to care for large numbers of people made seriously ill by COVID-19. Meanwhile, scientists are exploring potential treatments and clinical trials to test new therapies and vaccines are underway.

Below, you'll find answers to common questions all of us are asking. We will be adding new questions and updating answers as reliable information becomes available. Also see our podcasts featuring experts discussing coronavirus and COVID-19.

Symptoms, spread, and other essential information

What is coronavirus and how does it spread? What is COVID-19 and what are the symptoms? How long does coronavirus live on different surfaces? Take a moment to reacquaint yourself with basic information about this virus and the disease it causes.

Click here to read more about COVID-19 symptoms, spread, and other basic information.


Social distancing, hand washing, and other preventive measures

By now, many of us are taking steps to protect ourselves from infection. This likely includes frequent handwashing, regularly cleaning frequently touched surfaces, and social distancing. How do each of these measures help slow the spread of this virus, and is there anything else you can do?

Click here to read more about what you can do to protect yourself and others from coronavirus infection.


If you are at higher risk

Though no one is invulnerable, we've seen that older adults are at increased risk for severe illness or death from COVID-19. Underlying conditions, including heart disease, lung disease, and diabetes, increase risk even further in those who are older. In addition, anyone with an underlying medical condition, regardless of their age, faces increased risk of serious illness.

Click here to read more about what you can do if you are at increased risk for serious illness.


If you've been exposed, are sick, or are caring for someone with COVID-19

Despite your best efforts, you may be exposed to coronavirus and become ill with COVID-19. Or you may be in a position where you are caring for a loved one with the disease. It's important to know what to do if you find yourself in any of these situations. Stock up with medications and health supplies now, and learn the steps you can take to avoid infecting others in your household and to avoid getting sick yourself if you are caring for someone who is ill.

Click here to read more about what to do you if you have been exposed, are sick, or are caring for someone with COVID-19.


Treatments for COVID-19: What helps, what doesn't, and what's in the pipeline

While there are no specific treatments for COVID-19 at this time, there are things you can do to feel better if you become ill. In the meantime, researchers around the globe are looking at existing drugs to see if they may be effective against the virus that causes COVID-19, and are working to develop new treatments as well.

Click here to read more about measures that can help you feel better and treatments that are under investigation.


Coronavirus and kids:

So far, the vast majority of coronavirus infections have afflicted adults. And when kids are infected, they tend to have milder disease. Still, as a parent, you can't help but worry about the safety of your children. Many parents are also trying to find a balance between answering their children's questions about the pandemic and enforcing health-promoting behaviors and social distancing rules without creating an atmosphere of anxiety. Not to mention keeping kids engaged and entertained with schools closed and playdates cancelled.

Click here to read more about kids and the coronavirus outbreak.


Coping with coronavirus:

The news about coronavirus and its impact on our day-to-day lives has been unrelenting. There's reason for concern and it makes good sense to take the pandemic seriously. But it's not good for your mind or your body to be on high alert all the time. Doing so will wear you down emotionally and physically.

Click here to read more about coping with coronavirus.


New questions and answers

What types of masks are most and least effective?

We know that wearing masks can help prevent the spread of coronavirus by blocking droplets that are emitted when someone coughs, sneezes, talks, or breathes. But which masks are best and worst?

Researchers at Duke University created a simple setup that allowed them to count the number of droplet particles released when people spoke the phrase "Stay healthy, people" five times in a row. First, the study participants spoke without a mask, and then they repeated the same words, each time wearing one of 14 different types of face masks and coverings.

As expected, medical grade N95 masks performed best, meaning that the fewest number of droplets got through. They were followed by surgical masks. Several masks made of polypropylene, a cotton/propylene blend, and 2-layer cotton masks sewn in different styles also performed well.

Gaiters ranked dead last. In a surprise, they allowed more particles to get through than wearing no mask at all. Also called neck fleeces, gaiters tend to be made of lightweight fabric and are often worn by athletes. In the study, gaiters broke up larger droplets into smaller droplets that could spread more easily to others. Bandanas also ranked poorly, but better than no mask.

A couple of simple tests can help you gauge the effectiveness of your mask: If you can see through your mask when you hold it up to the light, or can breathe through it easily, it's probably not doing much to prevent spread.

Do people without symptoms have the same amount of coronavirus in their bodies as people with symptoms? And can people without symptoms spread the virus to others?

"Without symptoms" can refer to two groups of people: those who eventually do have symptoms (pre-symptomatic) and those who never go on to have symptoms (asymptomatic). During this pandemic, we have seen that people without symptoms can spread the coronavirus infection to others.

A person with COVID-19 may be contagious 48 to 72 hours before starting to experience symptoms. In fact, people without symptoms may be more likely to spread the illness, because they are unlikely to be isolating and may not adopt behaviors designed to prevent spread.

But what about people who never go on to develop symptoms? A recent study compared the amount of coronavirus in the nose, throat, and lungs of symptomatic and asymptomatic adults infected with SARS-CoV-2 (the COVID-19 coronavirus). Both groups of patients had similar amounts of virus in their bodies throughout the infection. This study did not look at the degree to which people with asymptomatic infections may infect others.

This study provides yet another reason to wear face masks and observe physical distancing. Both measures can help reduce the risk that someone who does not have symptoms will infect others.

Who do masks protect: the wearer, others, or both?

We've known for some time that masks help prevent people from spreading the coronavirus to others. Based on an analysis of existing information, a new study contends that masks may also protect mask wearers from becoming infected themselves.

Different masks, writes the study author, block viral particles to varying degrees. If masks lead to lower "doses" of virus being inhaled, then fewer people may become infected, and those who do may have milder illness.

Researchers in China experimented with hamsters to test the effect of masks. They put healthy hamsters and hamsters infected with SARS-CoV-2 (the COVID-19 coronavirus) in a cage, and separated some of the healthy and infected hamsters with a barrier made of surgical masks. Many of the "masked" healthy hamsters did not get infected, and those who did got less sick than previously healthy "maskless" hamsters.

A similar experiment cannot ethically be done in humans. But researchers have studied doses of flu virus and found that people who inhaled a higher dose of flu virus were more likely to get sick and experience symptoms. Observations of coronavirus outbreaks in processing plants and on cruise ships also support the idea that masks may help protect mask wearers.

Without more research, we can't be certain that masks protect the wearer. But we do know they don't hurt, and that they protect others.

What is the difference between a PCR test and an antigen test for COVID-19?

PCR tests and antigen tests are both diagnostic tests, which means that they can be used to determine whether you currently have an active coronavirus infection. However, there are important differences between these two types of tests.

PCR tests detect the presence of the virus's genetic material using a technique called reverse transcriptase polymerase chain reaction, or RT-PCR. For this test, a sample may be collected through a nasal or throat swab, or a saliva sample may be used. The sample is typically sent to a laboratory where coronavirus RNA (if present) is extracted from the sample and converted into DNA. The DNA is then amplified, meaning that many of copies of the viral DNA are made, in order to produce a measurable result. The accuracy of any diagnostic test depends on many factors, including whether the sample was collected properly, when during the course of illness the testing was done, and whether the sample was maintained in appropriate conditions while it was shipped to the laboratory. Generally speaking, PCR tests are highly accurate. However, it can take days to over a week to get the results of a PCR test.

Antigen tests detect specific proteins on the surface of the coronavirus. They are sometimes referred to as rapid diagnostic tests because it can take less than an hour to get the test results. Positive antigen test results are highly specific, meaning that if you test positive you are very likely to be infected. However, there is a higher chance of false negatives with antigen tests, which means that a negative result cannot definitively rule out an active infection. If you have a negative result on an antigen test, your doctor may order a PCR test to confirm the result.

It may be helpful to think of a COVID antigen test as you would think of a rapid strep test or a rapid flu test. A positive result for any of these tests is likely to be accurate, and allows diagnosis and treatment to begin quickly, while a negative result often results in further testing to confirm or overturn the initial result.

How long after I start to feel better will be it be safe for me to go back out in public again?

The most recent CDC guidance states that someone who has had COVID-19 can discontinue isolation once they have met the following criteria:

  1. It has been more than 10 days since your symptoms began.
  2. You have been fever-free for more than 24 hours without the use of fever-reducing medications.
  3. Other symptoms have improved.

The CDC is no longer recommending a negative COVID-19 test before going back out in public.

Anyone who tested positive for COVID-19 but never experienced symptoms may discontinue isolation 10 days after they first tested positive for COVID-19.

Even after discontinuing isolation, you should still take all precautions when you go out in public, including wearing a mask, minimizing touching surfaces, and keeping at least six feet of distance away from other people.

Are there any promising vaccines for COVID-19 under investigation?

Around the world, there are currently over 100 different COVID-19 vaccines in various stages of testing and development: preclinical work using animal models, followed by Phase 1 (safety), Phase 2 (optimal dose, schedule, and proof of concept), and Phase 3 (effectiveness, side effects) trials in humans.

The following three vaccine approaches are among the first to be tested clinically in the United States.

  • A vaccine created by Moderna in Cambridge, Massachusetts, uses a type of molecule called messenger RNA (mRNA) that can be mass-manufactured very rapidly. In this vaccine, mRNA induces human cells to make a molecule called the spike protein, which studs the surface of the coronavirus and enables it to enter human cells. The vaccine then triggers the immune system to make antibodies against the spike protein. Phase 1 human trials were started in March 2020 by the NIH. Initial results have shown the vaccine is safe and generates high levels of neutralizing antibodies. The vaccine is expected to enter Phase 3 clinical trials in July 2020.
  • A hybrid vaccine uses a modified, harmless form of a chimpanzee common-cold adenovirus to deliver the coronavirus spike protein into the body and to stimulate immune response. This platform was developed at the Jenner Institute at Oxford University in collaboration with AstraZeneca. Already in later stage clinical trials in many parts of the world, this vaccine is expected to enter clinical trials in the United States in August 2020.
  • Another hybrid vaccine uses a human common-cold adenovirus to deliver the coronavirus spike protein into the body. That platform was developed by Harvard Medical School scientists in collaboration with Johnson and Johnson. This vaccine launched Phase 1/2 clinical trials in July 2020.

In animal models, all three vaccines provide protective immunity against SARS-CoV-2, the COVID-19 virus. Upcoming trials will help establish their long-term effectiveness and potential side effects. A central question will be how long protection might last.

Can the COVID-19 virus spread through air conditioning?

We don't know for certain if the COVID-19 virus spreads through air conditioning. But we do know that when it's hot and humid, people are more likely to stay indoors, with the windows closed — giving the virus more opportunity to spread.

Coronavirus spreads through droplets that an infected person emits through coughs or sneezes and through smaller, infectious viral particles that can drift around in the air for several hours. Outdoors, air currents can scatter and dilute the virus, making transmission less likely. You're more likely to inhale the virus indoors, with the windows closed, whether or not you have the air conditioning on.

If you must be indoors with anyone outside of your household, increase air circulation by keeping the windows open as much as possible.

If I get sick with COVID-19, how long until I will feel better?

It depends on how sick you get. Most people with mild cases appear to recover within one to two weeks. However, recent surveys conducted by the CDC found that recovery may take longer than previously thought, even for adults with milder cases who do not require hospitalization. The CDC survey found that one-third of these adults had not returned to normal health within two to three weeks of testing positive for COVID-19. Among younger adults (ages 18 to 34) who did not require hospitalization and who did not have any underlying health conditions, nearly one in five had not returned to normal health within two to three weeks after testing positive for COVID-19. With severe cases, recovery can take six weeks or more.

Some people may experience longer-term physical, cognitive, and psychological problems. Their symptoms may alternately improve and worsen over time, and can include a variety of difficulties, from fatigue and trouble concentrating to anxiety, muscle weakness, and continuing shortness of breath.

What needs to happen before we have a vaccine for COVID-19?

A successful COVID-19 vaccine will safely and effectively stimulate the body's immune system to create antibodies that protect against the COVID-19 coronavirus. More than 100 COVID-19 vaccines are currently in various stages of development and testing, and more than one may eventually be approved.

Anti-virus vaccine development traditionally requires the following steps:

  • Pre-clinical testing: Animals are infected with the virus. Scientists study their immune response to see what aspects of the immune response might be critical for protection. Normally, a vaccine is first tested in animals. However, in the setting of a pandemic such as this one, the animal testing stage can be skipped.
  • Phase 1 trials: A vaccine is tested in small groups of people to determine what dose safely and consistently stimulates the immune system. At this stage, scientists don't yet know if the immune response triggered by the vaccine will protect against the virus.
  • Phase 2 trials: The vaccine is given to hundreds or thousands of people. Scientists continue to focus on whether the vaccine is safe and produces a consistent immune response.
  • Phase 3 trials: These trials typically enroll tens of thousands of people. This is the first phase that involves a placebo group. It compares the number of people who get sick in the vaccine group to the number of people who get sick in the placebo group. This is the only phase that can show whether or not the immune response triggered by the vaccine actually protects against infection in the real world.

Some researchers are combining trial phases in an effort to speed up the COVID-19 vaccine development process. In addition, the US government has created Operation WARP Speed, which will identify and support mass production of the most promising vaccines before they have been approved, so that they will be available quickly if they are ultimately found to be safe and effective. It's likely that a COVID-19 vaccine will be available before we know how long that vaccine's protective effect will last.

Do the antibodies produced by a person who has been infected with coronavirus protect them from becoming infected again?

Most people who are infected with the COVID-19 virus, whether or not they have symptoms, produce antibodies (proteins that fight infections). New research published in Nature Medicine looked at how long those antibodies last. Results from this small study suggest that levels of one type of antibody dropped sharply within two to three months. However, the decrease in neutralizing antibodies, which target the spike protein on the coronavirus and can help protect against reinfection, was much smaller.

Whether or not the remaining antibodies protect against reinfection, and for how long, is still unclear. It's possible that even low levels of neutralizing antibodies may be able to protect against reinfection. On the other hand, the presence of antibodies does not guarantee immunity.

Another consideration is that antibodies are only one part of the body's immune response. Memory B cells, for example, can quickly generate a strong antibody response to a virus the body has encountered before.


More about COVID-19


Podcast: Back to school: It's never been more complicated (recorded 7/30/2020)

Sending kids back to school in the fall is always a hopeful time in America. For most families, school is a vital part of the community. With the surge in coronavirus in many areas of the country, getting kids back in the classroom safely will require a major re-evaluation to reduce transmission rates that can impact people of all ages. We talked to Allan Geller, a senior lecturer in the Department of Social and Behavioral Sciences at Harvard's T.H. Chan School of Public Health. Like it or not, for school teachers and administrators, things are going to be different. Don't expect the traditional.

Podcast: Coronavirus Update: We're facing the start of a second wave (recorded 6/11/2020)

Dr. Ashish K. Jha, head of the Harvard Global Health Institute, offers information on where we are where we're going with the COVID-19 outbreak. Some take-aways:

  • Communications missteps by the WHO regarding asymptomatic transmission have been quickly corrected. Yes, you can catch COVID-19 from people who are not showing symptoms.
  • A second wave has begun, particularly in the south and Midwest. And calculations show we'll reach more than 200,000 COVID-19 related deaths by September.
  • Jha offers advice for parents, teachers and administrators on workable back-to-school scenarios.
  • We know you don't want to hear it, but COVID-19 will be a fact of global life for the rest of the year until a vaccine becomes widely available.

Podcast: COVID-19 and underlying conditions: Why symptoms may be more severe for people with chronic disease (recorded 5/6/20)

People who have diabetes, a heart condition, cancer, kidney disease or other underlying condition are impacted more severely if they contract the coronavirus. Harvard Medical School endocrinologist Dr. Enrique Caballero explains why. Dr. Caballero is on the staff of Brigham and Women's Hospital in Boston, Massachusetts, and is the director of diabetes education in the post-graduate medical education department at Harvard Medical School.

Podcast: Entendiendo como afecta la infección por COVID-19 a personas con enfermedades crónicas subyacentes (recorded 5/6/20)

Las personas que tienen diabetes, una afección del corazón o de los riñones u otra enfermedad crónica subyacente se ven afectadas más severamente si contraen el coronavirus. El Dr. Enrique Caballero, endocrinólogo de la Escuela de Medicina de Harvard explica la forma en que estas enfermedades favorecen infecciones severas por COVID-19 y como el coronavirus puede empeorar estas condiciones crónicas. El Dr. Caballero forma parte del personal del Hospital Brigham and Women's y es el director de educación en diabetes en el departamento de educación médica de posgrado de la Facultad de Medicina de Harvard en Boston, Massachusetts.


Reliable resources


Terms to know:

aerosols: infectious viral particles that can float or drift around in the air. Aerosols are emitted by a person infected with coronavirus — even one with no symptoms — when they talk, breathe, cough, or sneeze. Another person can breathe in these aerosols and become infected with the virus. Aerosolized coronavirus can remain in the air for up to three hours. A mask can help prevent that spread.

community spread (community transmission): is said to have occurred when people have been infected without any knowledge of contact with someone who has the same infection

contact tracing: a process that begins with identifying everyone a person diagnosed with a given illness (in this case COVID-19) has been in contact with since they became contagious. The contacts are notified that they are at risk, and may include those who share the person's home, as well as people who were in the same place around the same time as the person with COVID-19 — a school, office, restaurant, or doctor's office, for example. Contacts may be quarantined or asked to isolate themselves if they start to experience symptoms, and are more likely to be tested for coronavirus if they begin to experience symptoms.

containment: refers to limiting the spread of an illness. Because no vaccines exist to prevent COVID-19 and no specific therapies exist to treat it, containment is done using public health interventions. These may include identifying and isolating those who are ill, and tracking down anyone they have had contact with and possibly placing them under quarantine.

epidemic: a disease outbreak in a community or region

flattening the curve: refers to the epidemic curve, a statistical chart used to visualize the number of new cases over a given period of time during a disease outbreak. Flattening the curve is shorthand for implementing mitigation strategies to slow things down, so that fewer new cases develop over a longer period of time. This increases the chances that hospitals and other healthcare facilities will be equipped to handle any influx of patients.

incubation period: the period of time between exposure to an infection and when symptoms begin

isolation: the separation of people with a contagious disease from people who are not sick

mitigation: refers to steps taken to limit the impact of an illness. Because no vaccines exist to prevent COVID-19 and no specific therapies exist to treat it, mitigation strategies may include frequent and thorough handwashing, not touching your face, staying away from people who are sick, social distancing, avoiding large gatherings, and regularly cleaning frequently touched surfaces and objects at home, in schools, at work, and in other settings.

pandemic: a disease outbreak affecting large populations or a whole region, country, or continent

physical distancing: also called social distancing, refers to actions taken to stop or slow down the spread of a contagious disease. For an individual, it refers to maintaining enough physical distance (a minimum of six feet) between yourself and another person to reduce the risk of breathing in droplets or aerosols that are produced when an infected person breathes, talks, coughs, or sneezes.

presumptive positive test result: a positive test for the virus that causes COVID-19, performed by a local or state health laboratory, is considered "presumptive" until the result is confirmed by the CDC. While awaiting confirmation, people with a presumptive positive test result will be considered to be infected.

quarantine: separates and restricts the movement of people who have a contagious disease, have symptoms that are consistent with the disease, or were exposed to a contagious disease, to see if they become sick

SARS-CoV-2: short for severe acute respiratory syndrome coronavirus 2, SARS-CoV-2 is the official name for the virus responsible for COVID-19.

social distancing: also called physical distancing, refers to actions taken to stop or slow down the spread of a contagious disease. For an individual, it refers to maintaining enough physical distance (a minimum of six feet) between yourself and another person to reduce the risk of breathing in droplets or aerosols that are produced when an infected person breathes, talks, coughs, or sneezes. It is possible to safely maintain social connections while social distancing, through phone calls, video chats, and social media platforms.

virus: a virus is the smallest of infectious microbes, smaller than bacteria or fungi. A virus consists of a small piece of genetic material (DNA or RNA) surrounded by a protein shell. Viruses cannot survive without a living cell in which to reproduce. Once a virus enters a living cell (the host cell) and takes over a cell's inner workings, the cell cannot carry out its normal life-sustaining tasks. The host cell becomes a virus manufacturing plant, making viral parts that then reassemble into whole viruses and go on to infect other cells. Eventually, the host cell dies.

Image: Naeblys/Getty Images


Questions?

Harvard Health Publishing Coronavirus Resource Center Experts

The Harvard Health Publishing team would like to acknowledge the Harvard Medical School experts who have contributed their time and expertise: Steven A. Adelman, MD; Ashwini Bapat, MD; Suzanne Bertisch, MD, MPH; Emeric Bojarski, MD; Todd Ellerin, MD; Huma Farid, MD; Robert Gabbay, MD, PhD, FACP; Ellen S. Glazer, LICSW; Peter Grinspoon, MD; Sabra L. Katz-Wise, PhD; Anthony Komaroff, MD; Douglas Krakower, MD; Debi LaPlante, PhD; Howard E. LeWine, MD; Dara K. Lee Lewis, MD; Kristina Liu, MD, MHS; Julia Marcus, PhD,MPH; Luana Marques, PhD; Claire McCarthy, MD; Chris McDougle, MD; Babar Memon, MD, MSc; Uma Naidoo, MD; Janelle Nassim, MD; Vikram Patel, MBBS, PhD; Edward Phillips, MD; Shiv Pillai, PhD, MBBS; Lee H. Schwamm, MD; Howard J. Shaffer, PhD, CAS; John Sharp, MD; Robert H. Shmerling, MD; Jacqueline Sperling, PhD; Monique Tello, MD, MPH; Robyn Thom, MD; Karen Turner, OTR/L; Scott Weiner, MD; Anna R. Wolfson, MD.

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