Coronavirus Disease 2019 (COVID-19) Clinical Presentation

Updated: Jan 14, 2022
  • Author: David J Cennimo, MD, FAAP, FACP, FIDSA, AAHIVS; Chief Editor: Michael Stuart Bronze, MD  more...
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Presentations of COVID-19 range from asymptomatic/mild symptoms to severe illness and mortality. Common symptoms include fever, cough, and shortness of breath. [15]  Other symptoms, such as malaise and respiratory distress, have also been described. [31]

Symptoms may develop 2 days to 2 weeks after exposure to the virus. [15]  A pooled analysis of 181 confirmed cases of COVID-19 outside Wuhan, China, found the mean incubation period was 5.1 days, and that 97.5% of individuals who developed symptoms did so within 11.5 days of infection. [16]

The following symptoms may indicate COVID-19 [15] :

  • Fever or chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Fatigue
  • Muscle or body aches
  • Headache
  • New loss of taste or smell
  • Sore throat
  • Congestion or runny nose
  • Nausea or vomiting
  • Diarrhea

Other reported symptomsinclude the following:

  • Sputum production
  • Malaise
  • Respiratory distress
  • Neurologic (eg, headache, altered mentality) 

Wu and McGoogan reported that, among 72,314 COVID-19 cases reported to the CCDC, 81% were mild (absent or mild pneumonia), 14% were severe (hypoxia, dyspnea, >50% lung involvement within 24-48 hours), 5% were critical (shock, respiratory failure, multiorgan dysfunction), and 2.3% were fatal. [17] These general symptom distributions have been reconfirmed across multiple observations. [94, 95]

Clinicians evaluating patients with fever and acute respiratory illness should obtain information regarding travel history or exposure to an individual who recently returned from a country or US state experiencing active local transmission. [96]

Williamson and colleagues, in an analysis of 17 million patients, reaffirmed that severe COVID-19 and mortality was more common in males, older individuals, individuals in poverty, Black persons, and patients with medical conditions such as diabetes and severe asthma, among others. [97]

A multicenter observational cohort study conducted in Europe found frailty was a greater predictor of mortality than age or comorbidities. [98]

Type A blood has been suggested as a potential factor that predisposes to severe COVID-19, specifically in terms of increasing the risk for respiratory failure. Blood type O appears to confer a protective effect. [99, 100]

Patients with suspected COVID-19 should be reported immediately to infection-control personnel at their healthcare facility and the local or state health department. CDC guidance calls for the patient to be cared for with airborne and contact precautions (including eye shield) in place. [20] Patient candidates for such reporting include those with fever and symptoms of lower respiratory illness who have travelled from Wuhan City, China, within the preceding 14 days or who have been in contact with an individual under investigation for COVID-19 or a patient with laboratory-confirmed COVID-19 in the preceding 14 days. [96]

A complete or partial loss of the sense of smell (anosmia) has been reported as a potential history finding in patients eventually diagnosed with COVID-19. [18] A phone survey of outpatients with mildly symptomatic COVID-19 found that 64.4% (130 of 202) reported any altered sense of smell or taste. [19] In a European study of 72 patients with PCR results positive for COVID-19, 53 patients (74%) reported reduced olfaction, while 50 patients (69%) reported a reduced sense of taste. Forty-nine patients (68%) reported both symptoms. [101]



Physical Examination

Patients who are under investigation for COVID-19 should be evaluated in a private room with the door closed (an airborne infection isolation room is ideal) and asked to wear a surgical mask. All other standard contact and airborne precautions should be observed, and treating healthcare personnel should wear eye protection. [20]

The most common serious manifestation of COVID-19 upon initial presentation is pneumonia. Fever, cough, dyspnea, and abnormalities on chest imaging are common in these cases. [102, 103, 104, 105]

Huang and colleagues found that, among patients with pneumonia, 99% had fever, 70% reported fatigue, 59% had dry cough, 40% had anorexia, 35% experienced myalgias, 31% had dyspnea, and 27% had sputum production. [102]



Complications of COVID-19 include pneumoniaacute respiratory distress syndrome, cardiac injury, arrhythmia, septic shock, liver dysfunction, acute kidney injury, and multi-organ failure, among others.

Approximately 5% of patients with COVID-19, and 20% of those hospitalized, experience severe symptoms necessitating intensive care. The common complications among hospitalized patients include pneumonia (75%), ARDS (15%), AKI (9%), and acute liver injury (19%). Cardiac injury has been increasingly noted, including troponin elevation, acute heart failure, dysrhythmias, and myocarditis. Ten percent to 25 percent of hospitalized patients with COVID-19 experience prothrombotic coagulopathy resulting in venous and arterial thromboembolic events. Neurologic manifestations include impaired consciousness and stroke.

ICU case fatality is reported up to 40%. [94]  


As the COVID-19 pandemic has matured, more patients have reported long-term, post-infection sequelae. Most patients recover fully, but those who do not have reported adverse symptoms such as fatigue, dyspnea, cough, anxiety, depression, inability to focus (ie, “brain fog”), gastrointestinal problems, sleep difficulties, joint pain, and chest pain lasting weeks to months after the acute illness. Long-term studies are underway to understand the nature of these complaints. [106]  

Post-acute sequelae of SARS-CoV-2 (PASC) infection is the medical term for what is commonly called long COVID or "long haulers". The NIH includes discussion of persistent symptoms or organ dysfunction after acute COVID-19 within guidelines that discuss the clinical spectrum of the disease. [107]  

The UK National Institute for Health and Care Excellence (NICE) issued guidelines on care of long COVID that define the syndrome as: signs and symptoms that develop during or after an infection consistent with COVID-19, continue for more than 12 weeks, and are not explained by an alternative diagnosis. [108]  

An international web-based survey of respondents (n = 3762) with suspected and confirmed COVID-19 from 56 countries tallied prevalence of 205 symptoms in 10 organ systems, with 66 symptoms traced over 7 months. The most frequent symptoms reported after 6 months were fatigue (77.7%), postexertional malaise (72.2%), and cognitive dysfunction (55.4%). Nearly 50% were unable to return to work 6 months after infection. [109]  

A long-term follow-up study of adults with non-critical COVID-19 at 30 and 60 days post infection revealed ongoing symptoms in two thirds of patients. The most common symptoms included anosmia/ageusia in 28% (40/150) at Day 30 and 23% (29/130) at Day 60; dyspnea in 36.7% (55/150) of patients at day 30 and 30% (39/130) at day 60; and fatigue/weakness in 49.3% (74/150) at day 30 and 40% (52/130) at day 60. Persistent symptoms at day 60 were significantly associated with age 40 to 60 years, hospital admission, and abnormal auscultation at symptom onset. [110]  

A follow-up study of COVID-19 consequences in 1733 patients discharged from the hospital in Wuhan, China after 6 months reported fatigue or muscle weakness (63%), sleep difficulties (26%), and anxiety or depression (23%) were the most common symptoms. Lung function, as measured by CT showing interstitial change and 6-minute walking distance, was less than the lower limit of normal for 22% to 56% across different severity scales. [111]

A study of 55 patients from China looked at long-term pulmonary follow-up 3 months after discharge from a symptomatic COVID-19 illness. Patients’ mean age was 47 years, 42% were female, and 85% had moderate disease. Only nine patients (16.4%) had underlying comorbidities including hypertension, diabetes mellitus, and cardiovascular diseases, but none had preexisting pulmonary disease. None of the patients required mechanical ventilation. At 3 months, 71% still had abnormal chest CT scans, most commonly showing interstitial thickening. Spirometry was also checked in all patients. Lung function abnormalities were detected in 25.5%. Anomalies were noted in total lung capacity of four patients (7.3%), FEV1 of six patients (11%), FVC of six patients (11%), DLCO of nine patients (16%), and small airway function in seven patients (12%), despite most patients having no respiratory complaints. [112]  

These data are consistent with the findings of a study of 124 patients recovered from COVID-19 after 6 weeks in the Netherlands. The mean age was 59±14 years and 60% were male; 27 with mild, 51 with moderate, 26 with severe, and 20 with critical disease. Nearly all patients (99%) had improved imaging, but residual parenchymal abnormalities remained in 91% and correlated with reduced lung diffusion capacity in 42%. Twenty-two percent had low exercise capacity, 19% low fat-free mass index, and 36% had problems in mental and/or cognitive function. [113]  

The long-term effects of COVID-19 have also been observed after mild infection treated in the outpatient setting. In a longitudinal cohort study at the University of Washington, 177 participants completed a survey a median of 169 days after their COVID-19 diagnosis. Almost 85% were never admitted for treatment. One third reported persistent symptoms, and a similar number reported worsened quality of life. The most common symptom was fatigue. [114]

Future public health implications

Public health implications for long COVID need to be examined, as reviewed by Datta et al. As with other infections (eg, Lyme disease, syphilis, Ebola), late inflammatory and virologic sequelae may emerge. Accumulation of evidence beyond the acute infection and postacute hyperinflammatory illness is important to evaluate to gain a better understanding of the full spectrum of the disease. [115]  

Thrombotic manifestations of severe COVID-19 are caused by the ability of SARS-CoV-2 to invade endothelial cells via angiotensin-converting enzyme-2 (ACE-2), which is expressed on the surface of endothelial cells. Subsequent endothelial inflammation, complement activation, thrombin generation, platelet and leukocyte recruitment, and the initiation of innate and adaptive immune responses culminate in immunothrombosis, and can ultimately cause microthrombotic complications (eg, DVT, PE, stroke). [116]  

Kotecha et al describe patterns of myocardial injury in hospitalized patients with severe COVID-19 who had elevated troponin levels. During convalescence, myocarditis-like injury was observed, with limited extent and minimal functional consequence. However, in a proportion of patients, there was evidence of possible ongoing localized inflammation. Roughly 25% of patients had ischemic heart disease, of which two thirds had no previous history. [117]  


Clinicians, infectious disease specialists, and public health experts are examining the potential for patient reinfection with the SARS CoV-2 virus. [118]

Cases of reinfection with SARS CoV-2 have emerged worldwide. [119]  Several cases have shown differing viral genomes tested in the patient, which suggests reinfection rather than prolonged viral shedding. 

A case report showed a 42-year-old male who was infected with SARS CoV-2 on March 21, 2020 after a workplace exposure. The patient had symptom resolution of symptoms after 10 days with continued good health for 51 days. On May 24, 2020, the patient presented with symptoms suggestive of COVID-19 after a new household exposure. Upon testing via SARS-CoV-2 RT-PCR, the patient had confirmed positive COVID-19 with several potential genetic variations that differed from the SARS-CoV-2 strain sequenced from the patient in March. [120]  

In another case, a 33-year-old male in Hong Kong had contracted COVID-19 in March 2020, which was confirmed via saliva SARS-CoV-2 RT-PCR. The patient had symptom resolution along with two negative SARS-CoV-2 RT-PCR results by April 14, 2020. The patient experienced a second episode of COVID-19 in August 2020 after a trip to Spain. Although asymptomatic, the patient was tested upon returning to Hong Kong, and tested positive via SARS-CoV-2 RT-PCR. Genomic sequencing was performed on both RT-PCR specimens collected in March and August. The genomic analysis showed the two strains of SARS-CoV-2 (from March and August) belonged to different viral lineages, which suggests that the strain from the first episode differed from the strain in the second episode. [121]  

The Collaborative Study COVID Recurrences (COCOREC) group in France reported 11 virologically-confirmed cases of patients with a second clinically- and virologically-confirmed acute COVID-19 episode between April 6, 2020 and May 14, 2020. The letter does not describe confirmation with viral genomic sequencing to understand if the cases were a relapse of the initial infection or a new infection, however. [122]  

Two cases of reinfection have emerged in the United States, a 25-year-old man from Nevada and a 42-year-old man in Virginia. These cases were confirmed by gene testing that showed different strains of the SARS-CoV-2 virus during the two infection episodes in each patient. In these cases, the patients experienced more severe symptoms during their second infections. It is unclear if the symptom severity experienced the second time were related to the virus or the how the patients’ immune systems reacted. Vaccine development may need to take into account circulating viral strains. [119, 123]  

These case reports give insight to the possibility of reinfection. Further research to determine the prevalence of COVID-19 reinfections is needed, including the frequency at which they occur and longevity of COVID-19 immunity.