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COVID-19 (coronavirus disease 2019), formerly known as 2019-nCoV

Written by Ada’s Medical Knowledge Team

Updated on

  1. COVID-19
  2. Reported affected areas
  3. Causes and risks
  4. Signs and symptoms
  5. Diagnosis
  6. Treatment
  7. Prevention
  8. WHO “Public Health Emergency of International Concern” announcement

The following text is based on the evolving but still limited knowledge of the new coronavirus. It will be updated as new information becomes available.

COVID-19 (coronavirus disease 2019)

COVID-19 is the disease resulting from infection by a new respiratory virus (SARS-CoV-2) first identified on December 8th, 2019 in Wuhan, Hubei Province, China as the cause of a respiratory illness outbreak. The name was suggested by the WHO, using established guidelines that include being related to the disease, avoiding reference to people, places, or animals associated with the disease, and being easily pronounceable.[1]

Reported affected areas

So far, the majority of cases have occured in China. In the beginning only laboratory confirmed cases were counted there, while now all suspected cases with a clinical diagnosis of pneumonia are counting. These new cases have not necessarily been laboratory confirmed as having COVID-19.

Cases have also been detected in several other countries in Asia, as well as in Oceania, Europe, and North America. Further global spread is likely.[2]

Causes and risks

Coronaviruses are a large family of viruses that cause infection in a variety of animal species, including birds and mammals – such as camels, cats, cows, and bats. Coronaviruses can also spread between animals and humans, and in some cases, also between humans. This is rare, but in the past, has led to outbreaks (MERS-CoV and SARS).

Initially, many of the patients in the COVID-19 outbreak were linked to a large market selling seafood and live animals – suggesting it was spread by animal-to-person contact. However, the cases that followed have not had direct exposure to animal markets, indicating person-to-person transmission.[3] This has been observed both within and outside of China. When person-to-person spread occurred with MERS and SARS, it was thought to have happened mainly via respiratory droplets produced when an infected person coughs or sneezes, similar to how influenza and other respiratory pathogens spread.[4] Currently, it’s unclear how easily the new coronavirus spreads between people.

Signs and symptoms

From what we know so far, the virus can cause mild, flu-like symptoms such as fever, cough, difficulty breathing, muscle pain, and tiredness. Some cases also experienced diarrhea and nausea one to two days prior to the development of fever and dyspnea.[5]

Symptoms of COVID-19 include cough, sore throat, and shortness of breath.
Symptoms of the novel coronavirus

More serious cases develop severe pneumonia, acute respiratory distress syndrome, sepsis, and septic shock that can lead to the death of the patient. People with existing chronic conditions seem to be more vulnerable to severe illness.[6]

Reported pre-existing conditions (so far) include hypertension and other cardiovascular disorders, diabetes, liver disorders, and other respiratory diseases.[6]

Current estimates of the time between infection and onset of symptoms range from one to 12.5 days with average estimates of five to six days. While people are mostly infectious when they show (flu-like) symptoms, there are indications that some people might be able to transmit the virus without showing any symptoms or before the symptoms appear. If this is confirmed, it would make early detection of COVID-19 infections more difficult. However, it is not unusual for viral infections of this type – for example, as is also seen with measles.[6]

If you have these or similar symptoms, you can now use Ada for a free symptom assessment. Please keep in mind that these symptoms could also indicate the common cold and further testing will be necessary to diagnose COVID-19.


Laboratory testing of respiratory and blood samples confirm SARS-CoV-2 infection.[7]

Who should be tested for COVID-19?[8]

Patients who have a sudden onset of at least one of the following:

  • cough
  • sore throat
  • shortness of breath.

AND in the 14 days prior to the onset of symptoms, they fulfilled at least one of the following criteria:

  • had close contact with a COVID-19 patient (healthcare-associated exposure, working together in close proximity or sharing the same classroom environment, travelling together, or living in the same household)
  • had a history of traveling to areas with ongoing community transmission of COVID-19
  • worked in or attended a healthcare facility where patients with COVID-19 infections were being treated.

What to do if you fit these criteria?

  • As the measures differ between countries, contact your respective public health authority to get advice on what to do.
  • Before you go to a doctor’s office or the emergency room, call ahead and tell them about your recent travels and your symptoms, and then, follow their advice.
  • Avoid contact with others.
  • Do not travel while sick.
  • Cover your mouth and nose with a tissue or your sleeve (not your hands) when coughing or sneezing.
  • Wash hands often with soap and water for at least 20 seconds. Use an alcohol-based hand sanitizer if soap and water are not available.[8]


To date, there is no specific medicine recommended to prevent or treat the novel coronavirus. However, those infected with COVID-19 should receive appropriate care to relieve and treat symptoms, and those with severe illness should receive optimal supportive care. Some specific treatments are under investigation and will be tested through clinical trials.[9]


At present, there is no vaccine to prevent COVID-19. Avoiding exposure to the virus is the best way to prevent infection. Standard measures to prevent the spread of respiratory viruses apply, which include:

  • Wash hands frequently with soap and water for at least 20 seconds. If soap and water are not available, use an alcohol-based hand sanitizer.
  • Avoid touching your eyes, nose, and mouth with unwashed hands.
  • Avoid close contact with anyone who has fever and cough.
  • Stay home when you are sick.
  • Cover your cough or sneeze with a tissue, and then throw the tissue in the trash.
  • Clean and disinfect frequently touched objects and surfaces.[10]

For travelers going to China:

Several countries[8][11][12] currently recommend that individuals avoid non-essential travel to China. If travel to China cannot be avoided, or you are already in China, please note the following:

  • Avoid contact with sick people.
  • Discuss travel to China with your healthcare provider – older adults and travelers with underlying health issues may be at risk for a more severe disease.
  • Avoid animals (alive or dead), animal markets, and products that come from animals (such as uncooked meat).
  • Wash hands often with soap and water for at least 20 seconds and use an alcohol-based hand sanitizer if soap and water are not available.[8]

For even more details, read our Ada Editorial article on the novel coronavirus where one of our doctors, Dr. Gilsdorf, answers your most commonly asked questions.

WHO “Public Health Emergency of International Concern” announcement

This declaration is associated with some extra recommendations to the affected and neighboring countries – in response to the outbreak. Many countries are already implementing these measures, so the Public Health Emergency announcement has not had a large effect on those countries. A Public Health Emergency of International Concern is also linked to additional funding and resources to prevent and reduce the international spread of disease.

  1. World Health Organization. “WHO best practices for naming of new human infectious diseases”. 12 February 2020.

  2. European Centre for Disease Prevention and Control. “Novel coronavirus”. 12 February 2020.

  3. Centers for Disease Control and Prevention. “About 2019 Novel Coronavirus”. 6 February 2020.

  4. Centers for Disease Control and Prevention. “How 2019-nCoV Spreads”. 5 February 2020.

  5. JAMA Network. “Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus–Infected Pneumonia in Wuhan, China”. 7 February 2020.

  6. European Centre for Disease Prevention and Control. “Novel Coronavirus (2019-nCoV), Questions and Answers”. 9 February 2020.

  7. Centers for Disease Control and Prevention. “Novel Coronavirus - Situation Sumamry”. 7 February 2020.

  8. Center for Disease Control. "Travel Notices: Novel Coronavirus China". 4 February 2020.

  9. World Health Organization. Q&A on coronaviruses. 11 February 2020.

  10. Center for Disease Control. "About 2019-nCoV: Prevention & Treatment". 8 February 2020.

  11. Auswärtiges Amt. “China: Reise- und Sicherheitshinweise (Teilreisewarnung)”. 10 February 2020.

  12. GOV.UK. “Foreign travel advice: China”. 9 February 2020.

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