A fever, a cough and a stuffy nose could be any one of three common respiratory viruses. Sorting out flu vs COVID vs RSV matters because the answer changes what you can do next, especially when a baby, a grandparent or someone with asthma lives in the same home. At Palm Urgent Care on North Highland Avenue in National City, a clinician can examine you, order the right test and talk through treatment options in one visit.
Flu vs COVID vs RSV Symptoms Chart
All three viruses circulate in the fall and winter, and their symptoms overlap. This chart brings together what the CDC lists for flu, COVID-19 and RSV.
How quickly symptoms start
- Flu: usually about two days after infection (range one to four days), per the CDC, and often suddenly.
- COVID-19: 2 to 14 days after exposure. Symptoms may start mild and become more severe for some people.
- RSV: usually 4 to 6 days after infection, with symptoms arriving in stages rather than all at once.
Symptoms side by side
- Fever, cough, runny or stuffy nose: flu, COVID-19 and RSV
- Sore throat, body aches, headache and fatigue: flu and COVID-19
- Shortness of breath: a COVID-19 symptom, a flu warning sign, and possible as RSV progresses
- New loss of taste or smell: more common with COVID-19, though flu can cause it too
- Sneezing, wheezing and a lower appetite: RSV
- Vomiting or diarrhea: COVID-19, and flu, more often in children
What the chart cannot tell you
Comparing flu vs COVID vs RSV on paper only goes so far. The CDC states that you cannot tell flu from COVID-19 by symptoms alone, and testing is needed to confirm a diagnosis. RSV often looks like a cold at first, and in very young infants the only signs may be irritability, decreased activity and breathing difficulties.
Who Is at Higher Risk
- Flu: The CDC's list of people at increased risk for flu complications includes adults 65 and older, children younger than 5 (highest risk under 2), pregnant women and those up to two weeks after pregnancy, and people with asthma, chronic lung disease, diabetes, heart disease or a weakened immune system.
- COVID-19: The CDC names older adults (especially 75 and older), people not up to date on COVID-19 vaccines, and people with chronic lung disease, heart disease or a weakened immune system.
- RSV: Infants younger than 6 months and older adults are the most likely to need hospital care, per the CDC. The County of San Diego adds premature infants, young children with heart disease from birth or chronic lung disease such as asthma, and people with weakened immune systems.
Asthma deserves extra attention here. West National City is part of the state's Portside Environmental Justice Neighborhoods community, which the California Air Resources Board describes as having some of the highest asthma rates in the region, alongside emissions from the port, freight, rail and heavy truck traffic. For working and military families alike, a new infection in someone with asthma is a reason to get checked early.
Why Early Testing Matters for Treatment
- Flu: According to the CDC, antiviral medicine works best when started within two days after symptoms begin and can shorten illness by about a day. Starting later can still help people at higher risk or those who are very sick.
- COVID-19: The CDC says treatment must start within 5 to 7 days after symptoms begin. If you are at high risk, you do not need a positive test before talking with a clinician about treatment.
- RSV: There is no treatment made just for RSV, and most infections clear in a week or two, per the County, though antivirals can be used in severe, high-risk cases. RSV samples are most accurate in the first few days of symptoms, as MedlinePlus explains.
A clear answer also helps you skip treatment that will not work: the CDC states that antibiotics do not work on viruses, including flu.
Rapid Tests vs Lab Tests
Flu tests
The CDC explains that rapid influenza diagnostic tests return results in about 10 to 15 minutes but may be less accurate, so you could still have flu after a negative result. Rapid molecular tests take about 15 to 20 minutes and are more accurate, while lab RT-PCR tests take one to several hours. A clinician may also diagnose flu from your symptoms without a test.
COVID-19 tests
Antigen tests usually give results in 15 to 30 minutes, while molecular tests (NAATs, including PCR) are more likely to detect the virus, according to the CDC. One negative antigen test cannot rule out infection, so with symptoms the FDA recommends two negative antigen tests taken 48 hours apart.
RSV tests
Rapid RSV antigen tests can return results in an hour or less. More sensitive RT-PCR tests are often used for older children and adults, and a respiratory pathogens panel can check for RSV, flu and COVID-19 from one sample.
Lab testing and diagnostics are part of the care at Palm Urgent Care, National City, and your clinician will choose the test that fits your symptoms. Read our guide to lab testing at urgent care, or use our contact page to confirm which respiratory tests are available before a flu test in National City.
Emergency Warning Signs: When to Call 911
Urgent care is the right place for most fevers, coughs and congestion. Call 911 or go to the nearest emergency room for any of these warning signs from the CDC's flu and COVID-19 lists:
- Trouble breathing or shortness of breath
- Chest pain or pressure that does not go away
- New confusion, or trouble waking up or staying awake
- Lips, nail beds or skin that look pale, gray or blue
- Seizures
- Not urinating
- Severe weakness, unsteadiness or muscle pain
- Symptoms that improve, then return or get worse
In children, also watch for fast breathing, signs of dehydration, a fever above 104°F that does not come down with medicine, and any fever in a baby younger than 12 weeks. The CDC notes that RSV in infants younger than 6 months can cause pauses in breathing longer than 10 seconds, which needs emergency care.
Following the County's Weekly Respiratory Virus Report
The County of San Diego Health and Human Services Agency posts respiratory virus data, including test positivity and hospitalizations, and a Respiratory Virus Surveillance Report covering COVID-19, flu and RSV. The report is issued weekly on Thursdays from October through April and monthly the rest of the year.
The CDC notes that flu activity most often peaks between December and February, and RSV usually peaks in December and January. When local numbers climb, test promptly if a higher-risk family member gets sick. Whether you search for a flu test near me or a prueba de influenza for a relative who prefers Spanish, the advice is the same: earlier is better.
Frequently Asked Questions
How can I tell if I have the flu, COVID-19 or RSV?
Not reliably by symptoms alone. All three can cause fever, cough and congestion, and the CDC says testing is needed to confirm flu or COVID-19. A clinician can decide whether RSV testing also makes sense.
Can a rapid test give a false negative?
Yes. Rapid flu tests can miss infections, and one negative COVID-19 antigen test cannot rule out the virus. Your clinician may repeat the test or order a more sensitive molecular test.
What are RSV symptoms in adults?
Most adults have cold-like symptoms such as a runny nose, cough, sneezing and fever, and recover in a week or two. Older adults with heart or lung disease and adults with weakened immune systems face higher risk.
When should I go to the ER instead of urgent care?
Call 911 or go to the ER for trouble breathing, chest pain or pressure, new confusion, gray or blue lips or skin, seizures, or a baby with pauses in breathing. Without those signs, urgent care can usually help.
Sick and not sure which virus it is? Visit Palm Urgent Care, National City at 101 N Highland Ave, Suite F, for an exam and testing, and check the location page for hours, coverage and directions.
This article is for general information and is not a substitute for medical advice from a licensed clinician.