The most common signs of COVID-19 are fever, cough, sore throat, congestion, fatigue, headache, muscle aches, and a runny nose. Symptoms typically appear 3 to 6 days after exposure and last up to 10 days, though some people feel sick for longer. The virus can also cause less obvious symptoms involving the gut, the brain, and even the skin.
The Most Common Symptoms
COVID-19 shares many symptoms with the flu and common cold, which is why testing matters. The symptoms most people experience include:
- Fever or chills
- Cough
- Sore throat
- Congestion or runny nose
- Fatigue
- Headache
- Muscle or body aches
- Shortness of breath
Current variants, including the Omicron-related strains circulating now, produce roughly the same set of symptoms as earlier versions of the virus. Upper respiratory symptoms like sore throat and congestion tend to be prominent, while the dramatic loss of taste and smell that marked earlier waves still happens but is less common.
Less Obvious Signs
Not everyone gets the classic cold-like symptoms. COVID can also show up as digestive trouble: diarrhea, stomach pain, nausea, or constipation. Some people develop these gut symptoms before respiratory ones appear, or experience them without ever getting a cough at all.
Neurological symptoms are another less expected sign. Difficulty thinking clearly or concentrating (often called “brain fog”), dizziness, and headaches can all occur during acute infection. Loss of taste or smell, while less frequent with current variants, remains a hallmark that sets COVID apart from the flu and RSV, where it simply doesn’t occur.
How COVID Differs From the Flu and Colds
The flu hits fast. You can feel fine in the morning and be flat on your back by evening. COVID’s onset is more variable. Some people notice gradual worsening over a day or two, while others feel symptoms come on quickly. A regular cold almost always starts slowly, usually with a scratchy throat and sneezing.
The biggest distinguishing clue is still loss of taste or smell. Neither the flu nor RSV causes this. If food suddenly tastes like nothing, or your morning coffee has no aroma, COVID is the most likely explanation. That said, plenty of COVID cases never involve this symptom, so its absence doesn’t rule the virus out.
Shortness of breath is more common in COVID than in typical colds or even most flu cases, particularly when the infection moves deeper into the lungs. RSV can cause significant breathing difficulty too, but mainly in infants and older adults.
When Symptoms Appear and When to Test
With current Omicron-related variants, symptoms usually show up 3 to 6 days after exposure, which is shorter than the original virus. The FDA recommends testing immediately once symptoms begin, but a negative rapid test on day one doesn’t mean you’re in the clear. Viral levels may still be too low for an at-home antigen test to detect.
If your first rapid test is negative and you still feel sick, test again at least 48 hours later. It can take 2 to 5 days, sometimes longer, for the virus to build up enough to register on an antigen test. Two negative tests spaced 48 hours apart give you a much more reliable answer than a single negative result.
Signs in Children
Kids with COVID generally experience the same symptoms as adults: fever, cough, runny nose, and fatigue. Many children have mild illness or no symptoms at all. But parents should watch for a rare but serious complication called Multisystem Inflammatory Syndrome in Children (MIS-C), which can develop up to two months after a COVID infection.
MIS-C involves widespread inflammation throughout the body and requires hospital treatment. Warning signs include persistent fever along with at least two of the following: severe stomach pain, vomiting or diarrhea, red bloodshot eyes, redness or swelling of the lips and tongue, redness or swelling of the hands or feet, and heart-related symptoms like chest pain. If a child who recently had COVID develops a combination of these signs, they need immediate medical attention.
How Vaccination Changes the Picture
Vaccinated people still catch COVID, but their symptoms tend to be milder and resolve faster. A study of healthcare workers published in BMJ Open found that vaccinated participants were 30% less likely to still have symptoms six weeks after getting sick compared to unvaccinated participants. Vaccinated workers also returned to work a median of two days sooner.
Specific symptoms that lingered more in unvaccinated people included shortness of breath, muscle weakness, fatigue, chills, loss of taste or smell, headache, and nausea. Neurological symptoms like brain fog were also significantly less common in the vaccinated group at the six-week mark, with a roughly 29% reduction in risk.
Emergency Warning Signs
Most COVID infections resolve at home. But certain symptoms signal that the body is in serious trouble and needs emergency care. Call 911 if you or someone you’re caring for develops:
- Trouble breathing or shortness of breath at rest
- Persistent pain or pressure in the chest
- New confusion or difficulty staying alert
- Inability to wake up or stay awake
- Pale, gray, or blue-tinted skin, lips, or nail beds
Blue or gray discoloration of the lips and nail beds indicates low oxygen levels and is one of the most urgent signs. On darker skin tones, this color change may be easier to spot on the nail beds, gums, or around the eyes rather than on the lips. These signs can develop suddenly even after several days of what seemed like a mild illness, so continue monitoring throughout the course of infection.