Symptoms of COVID-19

Symptoms of COVID-19 are variable, ranging from mild symptoms to severe illness. Common symptoms include fever, cough, fatigue, breathing difficulties, and loss of smell and taste. People with the same infection may have different symptoms, and their symptoms may change over time. For example, one person may have a high fever, a cough, and fatigue, and another person may have a low fever at the start of the disease and develop difficulty breathing a week later. However, in people without prior ears, nose, and throat (ENT) disorders, loss of taste combined with loss of smell is associated with COVID-19 with a specificity of 95%.

As is common with infections, there is a delay, known as the incubation period, between the moment a person first becomes infected and the appearance of the first symptoms. The median incubation period for COVID-19 is four to five days. Most symptomatic people experience symptoms within two to seven days after exposure, and almost all symptomatic people will experience one or more symptoms before day twelve.

Around one in five people are infected with the virus but do not develop noticeable symptoms at any point in time. These asymptomatic carriers tend not to get tested, and they can spread the disease. Other infected people will develop symptoms later (called pre-symptomatic) or have very mild symptoms, and can also spread the virus.

Initial symptoms
Some symptoms of COVID-19 can be relatively non-specific; the two most common symptoms are fever (88 percent) and dry cough (68 percent). Among those who develop symptoms, approximately one in five may become more seriously ill and have difficulty in breathing. Emergency symptoms include difficulty breathing, persistent chest pain or pressure, sudden confusion, difficulty waking, and bluish face or lips; immediate medical attention is advised if these symptoms are present. Further development of the disease can lead to complications including pneumonia, acute respiratory distress syndrome, sepsis, septic shock, and kidney failure.

Some symptoms usually appear sooner than others. In August 2020, scientists at the University of Southern California reported the "likely" order of initial symptoms of the COVID-19 disease as a fever followed by a cough and muscle pain, and that nausea and vomiting usually appear before diarrhoea. This contrasts with the most common path for influenza where it is common to develop a cough first and fever later.

Fever
Fever is the most common symptom of COVID-19. The fever may be high or low. Most people with COVID-19 develop a fever at some point.

Respiratory
Most people with COVID-19 also have a cough, which could be either dry or a productive cough.

Some symptoms, such as difficulty breathing, are more common in patients who need hospital care. Shortness of breath tends to develop later in the illness.

Loss of smell or taste
About 40% of people temporarily lose their sense of smell (called anosmia), experience changes in how food tastes (dysgeusia), or have other disturbances to their normal abilities to smell or taste. This symptom, if it is present at all, often appears early in the illness. A disturbance in smell or taste is more commonly found in younger people, and perhaps because of this, it is associated with a lower risk of medical complications. Although most people with COVID-19 do not experience these symptoms, it is an unusual symptom for other respiratory diseases, so it is used for symptom-based screening.

Neurological symptoms
Patients with COVID-19 can present with neurological symptoms that can be broadly divided into central nervous system involvement, such as headache, dizziness, altered mental state, and disorientation, and peripheral nervous system involvement, such as anosmia and dysgeusia.

Skin rashes
Various skin rashes have been observed in COVID-19 patients, including morbilliform rash, livedo reticularis, and vesicular blisters. The so-called "COVID toes" are pink to violaceous papules arising on the hands and feet. These chilblain-like lesions often occur only in younger patients and do not appear until late in the disease or during convalescence.

Other
Other typical symptoms include fatigue, and muscle and joint pains.

Other symptoms are less common among people with COVID-19. Some people experience gastrointestinal symptoms such as loss of appetite, diarrhoea, or nausea. Some people have a sore throat, headache, or vertigo. Less common symptoms include chills, vomiting, coughing out blood, diarrhea, and rash.

Complications
Complications may include pneumonia, acute respiratory distress syndrome (ARDS), multi-organ failure, septic shock, and death.

Cardiovascular complications may include heart failure, arrhythmias, heart inflammation, and blood clots.

Approximately 20–30% of people who present with COVID-19 have elevated liver enzymes reflecting liver injury.

Neurologic manifestations include seizure, stroke, encephalitis, and Guillain–Barré syndrome (which includes loss of motor functions).

Following the infection, children may develop paediatric multisystem inflammatory syndrome, which has symptoms similar to Kawasaki disease, which can be fatal.

Longer-term effects
Some early studies suggest between 1 in 5 and 1 in 10 people with COVID-19 will experience symptoms lasting longer than a month. A majority of those who were admitted to hospital with severe disease report long-term problems including fatigue and shortness of breath About 5-10% of patients admitted to hospital progress to severe or critical disease, including pneumonia and acute respiratory failure.