COVID-19 causes a range of symptoms that overlap heavily with colds and flu, making it hard to distinguish without a test. The most common ones are fever, cough, sore throat, congestion, fatigue, and body aches. Symptoms can vary depending on which variant is circulating and whether you’ve been vaccinated, but the general pattern has shifted over time from a lung-focused illness toward something that feels more like an upper respiratory infection.
The Most Common Symptoms
The CDC lists these as possible COVID-19 symptoms:
- Fever or chills
- Cough
- Shortness of breath or difficulty breathing
- Sore throat
- Congestion or runny nose
- New loss of taste or smell
- Fatigue
- Muscle or body aches
- Headache
- Nausea or vomiting
- Diarrhea
Not everyone gets all of these, and some people test positive with barely any symptoms at all. The combination that shows up most often now is sore throat, cough, and fatigue, which is why so many people initially assume they just have a cold.
How Symptoms Have Changed Over Time
Early in the pandemic, losing your sense of taste or smell was a hallmark sign of COVID. That’s become much less common. During the Delta wave, about 34% of confirmed cases reported losing smell or taste. With Omicron and its descendants, that dropped to around 13%. Sore throat, on the other hand, became nearly twice as likely with Omicron compared to Delta.
Shortness of breath has also become less prominent. Earlier variants attacked the lungs more aggressively, while newer variants tend to cause upper airway symptoms like throat pain, nasal congestion, and cough. Fever remains common but is not universal. Roughly 29% of Omicron cases reported fever in one large study from England.
The takeaway is that COVID today typically feels like a bad cold or mild flu for most vaccinated people. That doesn’t mean it can’t still cause serious illness, but the symptom profile has shifted away from the severe respiratory distress that defined early waves.
Gut Symptoms Are More Common Than You’d Think
COVID is not just a respiratory illness. About 40% of patients experience gastrointestinal symptoms, primarily loss of appetite, nausea, vomiting, and diarrhea. Early reports from Wuhan put diarrhea at only 3% of cases, but later studies from the U.S. and China found that 50 to 60% of patients had at least one digestive symptom. Some people develop nausea or diarrhea before any cough or fever appears, which can delay recognition that they have COVID.
The virus is able to infect the digestive tract because the protein it uses to enter cells is found not only in the lungs but also in the lining of the gut, kidneys, heart, and blood vessels. This is why COVID can cause such a wide range of symptoms across different organ systems.
Why COVID Affects So Many Body Systems
The virus enters human cells by latching onto a specific protein found on cell surfaces throughout the body. This protein is present in the lungs, but also in the heart, kidneys, blood vessel walls, and intestines. Once the virus gets inside these cells, it disrupts the protein’s normal function, which is to help regulate blood pressure and inflammation.
When that protective function gets knocked out, inflammation ramps up. In severe cases, this triggers a chain reaction: blood vessels become inflamed, clotting pathways activate abnormally, and immune cells flood into the lungs, heart, and kidneys. This process explains why some patients develop chest pain, kidney problems, or blood clots, even though COVID starts as a respiratory infection.
How Long Before Symptoms Appear
Most people develop symptoms within 2 to 5 days of exposure, though it can take up to 14 days in some cases. Newer variants tend to have shorter incubation periods than the original strain, so symptoms often appear within 2 to 3 days of being exposed.
If you develop symptoms and want to test, keep in mind that a single negative rapid test doesn’t rule out COVID. The FDA recommends two negative antigen tests taken 48 hours apart if you have symptoms. If you don’t have symptoms but were exposed, three tests spaced 48 hours apart are recommended. Testing too early, before the virus has had time to build up in your system, is the most common reason for false negatives.
Emergency Warning Signs
Most COVID infections resolve on their own within a week or two. But certain symptoms signal that the illness is becoming dangerous and requires immediate medical attention:
- Trouble breathing or shortness of breath at rest
- Persistent pain or pressure in the chest
- New confusion or difficulty thinking clearly
- Inability to wake up or stay awake
- Lips, nail beds, or skin turning pale, gray, or blue (this can be harder to spot on darker skin tones, so check the nail beds and lips closely)
When Symptoms Don’t Go Away
For some people, symptoms persist for weeks or months after the initial infection clears. This is known as long COVID, and over 200 different symptoms have been reported. The most common are fatigue, brain fog (difficulty concentrating or thinking clearly), breathlessness, muscle and joint pain, headaches, and sleep problems.
Some people develop clusters of symptoms that tend to appear together. Dizziness, heart palpitations, and feeling lightheaded when standing up often occur as a group, related to the body’s difficulty regulating heart rate and blood pressure after infection. Others experience a pattern where physical or mental effort causes a delayed crash in energy, sometimes lasting days.
Long COVID was more common with pre-Omicron variants, affecting roughly 35% of those infected in one large meta-analysis. With Omicron-era infections, that dropped to about 23%. Fatigue is the single most common lingering symptom regardless of which variant caused the infection. Brain fog and sleep problems also rank consistently high. Earlier variants were more strongly linked to lasting loss of smell and breathing difficulties, while Omicron-era long COVID is more associated with brain fog and nerve-related symptoms like tingling or numbness.