Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease was first identified in December of 2019 in Wuhan, the capital of China’s Hubei province, and has since spread globally, resulting in the ongoing 2019–20 coronavirus pandemic. Common symptoms include fever, cough, and shortness of breath. Other symptoms may include fatigue, muscle pain, diarrhea, sore throat, loss of smell, and abdominal pain. The time from exposure to onset of symptoms is typically around five days but may range from two to fourteen days. While the majority of cases result in mild symptoms, some progress to viral pneumonia and multi-organ failure. As of 14 April 2020, more than 1.92 million cases have been reported across 210 countries and territories, resulting in over 119,000 deaths. More than 453,000 people have recovered.
Signs and symptoms
Those infected with the virus may be asymptomatic or develop flu-like symptoms such as fever, cough, fatigue, and shortness of breath. Emergency symptoms include difficulty breathing, persistent chest pain or pressure, confusion, difficulty walking, and bluish face or lips; immediate medical attention is advised if these symptoms are present. Less commonly, upper respiratory symptoms—such as sneezing, runny nose, or sore throat—may be seen. Symptoms such as nausea, vomiting, and diarrhea have been observed in varying percentages. Some cases in China initially presented only with chest tightness and palpitations. In March 2020 there were reports indicating that loss of the sense of smell (anosmia) may be a common symptom among those who have mild disease, although not as common as initially reported. In some, the disease may progress to pneumonia, multi-organ failure, and death. In those who develop severe symptoms, time from symptom onset to needing mechanical ventilation is typically eight days.
Some details about how the disease is spread are still being determined. The WHO and the U.S. Centers for Disease Control and Prevention (CDC) say it is primarily spread during close contact and by small droplets produced when people cough, sneeze or talk; with close contact being within 1–3 m (3 ft 3 in–9 ft 10 in). A study in Hong Kong observed that the virus was present in most patients’ saliva in quantities reaching 100 million virus strands per 1 mL. Loud talking releases more droplets than normal talking. A study in Singapore found that an uncovered cough can lead to droplets traveling up to 4.5 meters (15 feet). A second study, produced during the 2020 pandemic, found that advice on the distance droplets could travel might be based on old 1930s research which ignored the protective effect and speed of the warm moist outbreath surrounding the droplets. This study found that an uncovered cough or sneeze can travel up to 8.2 meters (27 feet).
The WHO has published several testing protocols for the disease. The standard method of testing is a real-time reverse transcription-polymerase chain reaction (RRT-PCR). The test is typically done on respiratory samples obtained by a nasopharyngeal swab, however, a nasal swab or sputum sample may also be used. Results are generally available within a few hours to two days. Blood tests can be used, but these require two blood samples taken two weeks apart and the results have little immediate value. Chinese scientists were able to isolate a strain of the coronavirus and publish the genetic sequence so laboratories across the world could independently develop polymerase chain reaction (PCR) tests to detect infection by the virus. As of 4 April 2020, antibody tests (which may detect active infections and whether a person had been infected in the past) were in development, but not yet widely used. The Chinese experience with testing has shown the accuracy is only 60 to 70%. The FDA approved the first point-of-care test on 21 March 2020 for use at the end of that month.