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1. What are the symptoms of COVID-19?

  • Fever, dry cough, fatigue and loss of appetite are the most common symptoms.
  • Sore throat and dry cough may be the first symptoms.
  • Headache, confusion, runny nose, muscle aches, diarrhea, and nausea and vomiting can occur but are less common.
  • Loss of taste and smell
  • Shortness of breath is reported by 30-40% of patients. If pneumonia develops, shortness of breath can get much worse requiring hospital treatment with oxygen or even mechanical ventilation.
  • It should be noted that some patients diagnosed with COVID-19 have not yet developed symptoms (pre-symptomatic).
  • Also, about 35% of people infected with the virus that causes COVID-19 do not develop symptoms (asymptomatic).




2. What laboratory and imaging findings are characteristic of COVID-19?

  • Lymphopenia is the most common laboratory finding and may be present in up to 83% of hospitalized patients.
  • Elevated WBCs (white blood cells), LDH (lactate dehydrogenase), D-dimer, CRP (C-reactive protein), and ferritin may be associated with worse illness severity.
  • Chest x-ray may be normal early in the disease but progresses to bilateral, airspace consolidation.
  • Chest CT scan is often normal early in the disease. As the disease progresses chest CT scan abnormalities (eg, peripheral ground glass opacities) may develop but are not specific and overlap with other infections. Therefore, the American College of Radiology does not recommend chest CT for screening or as a first-line diagnostic test for COVID-19.




3. What proportion of COVID-19 cases are asymptomatic carriers?

Asymptomatic infection seems to be quite common, with reported incidence ranging from 13% to > 50%. However, because asymptomatic people have typically not been tested, the actual incidence is unknown. According to the CDC, the best estimate is that about 35% of people infected with the virus that causes COVID-19 are asymptomatic. Some patients diagnosed during the asymptomatic period progressed to symptomatic disease while others remained without symptoms.




4. What’s the incubation period for COVID-19?

  • An average of about 4 to 5 days, and almost always between 1 and 14 days.
  • Almost 98% of people who develop symptoms will do so in 12 days or less after they become infected.




5. What’s the case fatality rate for COVID-19, and what are significant risk factors for mortality?

The Case Fatality Rate (%) = the number of deaths / the number of confirmed COVID-19 cases x 100 and therefore will depend on the number of people tested and their clinical status (ie, testing more minimally symptomatic or asymptomatic people will lead to lower case fatality estimates than when testing is concentrated on highly symptomatic patients as was done earlier in the pandemic). It is likely that many cases have not been tested and thus identified, whereas the number of deaths attributed to COVID-19 are more accurately identified. Thus, the apparent risk of death varies widely depending on how much testing is done in a given region.

The risk of a COVID-19 infection resulting in death varies widely by a person's age and overall health. Older people are much more likely to die. Although death is uncommon in younger people, it does occur. We don’t fully understand why some younger people are susceptible.

Other factors that can make it more likely to have serious illness or death from COVID-19 infection include

  • Heart and lung disorders
  • Stroke and cerebrovascular disorders
  • Disorders or use of drugs that interfere with the immune system
  • HIV infection
  • Organ transplant or stem cell transplant
  • Current or previous cigarette smoking
  • Chronic kidney disease
  • Diabetes
  • Cancer
  • Liver disease
  • Dementia or other neurologic conditions
  • Down syndrome
  • Overweight (body mass index [BMI] between 25 kg/m2 and 30 kg/m2), obesity (BMI between 30 kg/m2 and < 40 kg/m2), and especially severe obesity (BMI of 40 kg/m2 or above)
  • Pregnancy and recently pregnant women (for at least 42 days after end of pregnancy)
  • Substance abuse disorders (eg, alcohol, opioid, or cocaine use disorders)
  • Sickle cell disease or thalassemia

People who have these disorders may be able to decrease their risk by keeping the disorder under control (for example, maintaining the best levels of blood sugar or blood pressure).



6. How long does the COVID-19 illness last?

Much about this is still unknown. However, mild disease tends to subside in about 2 weeks. If disease is severe, median time to development of dyspnea is 5 to 8 days and to acute respiratory distress syndrome (ARDS) is 8 to 12 days. Among hospitalized patients, 26% to 32% were admitted to the ICU. Mortality among ICU patients ranges from 39% to 72%. The median length of hospitalization among survivors was 10 to 13 days.

Some patients continue to have symptoms such as fatigue, headaches, and shortness of breath for weeks to months after recovery.



7. What precautions should I take to prevent COVID-19 in clinical practice?

Follow the procedures and guidelines of your particular institution and practice, but in general, in addition to routine precautions of frequent, thorough handwashing and surface disinfecting, CDC recommendations ( include the following:

  • Encourage employees to get vaccinated
  • Use telemedicine as much as possible (eg, for follow-ups, triage of complaints).
  • Post signs at entrances and in waiting areas about prevention actions.
  • Allow patients to wait outside or in the car if they are medically able.
  • Establish a separate, well-ventilated triage area with some barrier between patient and staff.
  • In the waiting area and patient rooms, provide tissues, alcohol-based hand rub, soap at sinks, and trash cans. Place chairs 6 feet (1.8 meters) apart, when possible. Use barriers (like screens), if possible.
  • Screen patients for respiratory symptoms and fever or other signs of infectious illness and isolate symptomatic patients as soon as possible.
  • For COVID-19 positive patients, undiagnosed patients whose symptoms could be COVID-19, and patients within high-risk units (eg, ED, ICU), wear personal protective equipment (PPE), including a respirator (eg, N-95 or similar level of protection), face shield, gown, and gloves. Change PPE, at a minimum gown and gloves, between patients, washing hands before and after. If supplies of respirators are insufficient, change respirator at least daily and follow CDC guidance on cleaning and reuse ( as well as CDC guidance on optimizing the supply of PPE (

  How to Don and Doff PPE

  Based on NEJM

Put on PPE

  1. Put on protective gown
  2. Wash hands with soap and water or cleanse with an alcohol-based solution
  3. Put on nonsterile gloves
  4. Put on mask with a rating of N95 or higher, as recommended by the CDC
  5. Put on face shield

Remove PPE

  1. Remove gown and gloves
  2. Wash hands with soap and water or cleanse with an alcohol-based solution
  3. Put on a new pair of gloves
  4. Remove face shield and either dispose or clean and store in accordance with your institution’s guidelines
  5. Remove gloves
  6. Again, wash or cleanse hands
  7. Put on another pair of gloves
  8. Remove mask and either dispose or clean and store in accordance with your institution’s guidelines
  9. Remove gloves
  10. Again, wash or cleanse hands

  • To avoid transmission between health care facilities and home, health care workers should change out of street clothes on arrival and put them back on only for the trip home, at which time they should be immediately removed and washed.
  • For low-risk patients and settings (eg, office visits or rounds on patients without manifestations of infection) if distancing precautions cannot be observed, then clinicians should wear gloves and respirator because of the presumed possibility of asymptomatic infection.



8. What is the incidence of COVID-19 in children?

While it appears that children are at similar risk of infection from COVID-19 as adults, it is not possible to know the true incidence of infection; given that disease manifestations in children are much milder, testing is done less often in children. Studies show that 16% to 45% of children with SARS-CoV-2 infection are asymptomatic. A  study in Pediatrics (DOI: 10.1542/peds.2020-0702), based on the experience in China with more than 2,000 children under the age of 18, showed that children of all ages appeared susceptible to COVID-19. More than a third of the children tested were confirmed to have been infected with the virus. Greater than 90% of pediatric patients experienced asymptomatic, mild, or moderate disease, while around 6% of children developed severe or critical illness.



9. Can pets get COVID-19 or spread it to people?

A small number of pets worldwide, including cats and dogs, have been reported to be infected with the virus that causes COVID-19, mostly after close contact with people with COVID-19. The virus that causes COVID-19 can spread from people to animals in some situations. However, the risk of animals spreading COVID-19 to people is considered to be low. Until we learn more about how this virus affects animals, the CDC recommends ( treating pets as you would other human family members to protect them from a possible infection. They suggest that pets not interact with people or animals outside the household. People with COVID-19 infection should limit contact with their pets. 



10. Are patients who recover from COVID-19 clinical infection immune? How about asymptomatic carriers?

Antibodies to SARS CoV-2 develop within a few days of infection, including in asymptomatic people. However, it is too early to tell whether antibody titers will be adequate to induce immunity to repeat infection and, if so, for how long. Studies done of other human coronavirus infections showed that immunity to the strains that cause colds typically lasts only a few months. Studies following the original SARS outbreak in the early 2000s showed that antibody levels to that coronavirus dropped significantly after about three years. The best current estimate is that most patients who had COVID-19 infection will have some immunity but that it is probably not lifelong.  



11. How important are social distancing and face masks for people who are vaccinated?

According to the CDC, people who are fully vaccinated can

  • Resume activities that they did prior to the pandemic
  • Resume activities without wearing a mask or staying 6 feet apart, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance



12. Who should have a COVID-19 test?

The following patients should have SARS-CoV-2 testing with viral tests (ie, nucleic acid or antigen tests) 

Practitioners are also encouraged to test for other causes of respiratory illness such as influenza and bacterial pneumonia.



13. What is the role of the COVID-19 antibody test?

Tests for SARS-CoV-2 antibodies are now available. As with other serologic tests for infections, this test is good for diagnosing previous infection, but because of the lag in developing antibody titers is not a good test for initial diagnosis and/or screening.

One use of antibody assays is for a person suspected to have post-infectious syndrome (eg, multisystem inflammatory syndrome in children) caused by SARS-CoV-2 infection.

It is, of course, too early to tell what titer of antibodies is protective and for how long.


COVID-19 Resources Home Page