This is Part 1 of a new series for Brooklyn and Queens families on getting through respiratory season. Over the coming weeks we’ll cover this year’s vaccines, when a cough belongs in urgent care versus the ER, how to handle the school-season sick cycle, and what to do if you’re higher risk. We start with the question we hear most from October through March: what is this, actually?
Four Illnesses, One Set of Symptoms
Sore throat, cough, congestion, fever, fatigue. Influenza, the common cold, COVID-19, and RSV all produce some version of that list, which is why guessing from symptoms alone is genuinely difficult — even for clinicians. There is no combination of symptoms that reliably tells the four apart every time.
That said, there are patterns worth knowing. They won’t give you a diagnosis, but they’ll tell you how worried to be and how quickly to act — and that’s usually the decision you’re actually trying to make at 9pm on a Tuesday.
The Single Most Useful Clue: How Fast It Started
If you remember one thing from this post, make it this. Onset speed is the most telling difference between flu and everything else.
Flu tends to arrive like a switch flipping. People often describe knowing the hour it started — fine at lunch, flattened by dinner, with fever and deep body aches. A cold builds gradually over a day or two, usually starting in the nose and throat. COVID and RSV fall in between and vary a lot from person to person.
That abrupt, hit-by-a-truck onset with fever and aches is the closest thing to a flu signature there is.
How They Typically Compare
| Common Cold | Influenza (Flu) | COVID-19 | RSV | |
|---|---|---|---|---|
| Onset | Gradual, over 1–3 days | Abrupt, often within hours | Variable | Gradual |
| Fever | Uncommon in adults | Common, often higher | Common | Sometimes, usually mild |
| Body aches | Mild if any | Often prominent | Common | Mild |
| Sneezing & runny nose | Usually the main event | Possible, not dominant | Common | Very common |
| Exhaustion | Mild | Often severe, can linger | Often significant | Mild to moderate |
| Wheezing | Uncommon | Uncommon | Possible | Common, especially in babies |
| Who it hits hardest | Generally mild for most | Young children, 65+, chronic conditions, pregnancy | 65+, chronic conditions, immunocompromised | Infants under 1, adults 65+ |
These are typical patterns, not diagnostic rules. Any of these illnesses can present unusually, and symptoms overlap heavily.
The RSV misconception: a lot of people think of RSV as a baby illness. In healthy adults it usually is just a bad cold. But RSV is also one of the leading causes of hospitalization in infants under one year old, and it sends a significant number of adults over 65 to the hospital every season too. Same virus, very different stakes depending on who catches it.
Does Knowing Which One It Is Actually Change Anything?
Honest answer: sometimes yes, sometimes no — and it depends almost entirely on who you are.
For a healthy adult with mild symptoms, a test result often doesn’t change much. The care is largely the same: rest, fluids, fever control, and time. Testing may still be worth it if you live with someone vulnerable, need documentation for work or school, or simply want to know whether to isolate.
For higher-risk people, it can matter a great deal. If you’re 65 or older, pregnant, immunocompromised, or living with asthma, COPD, diabetes, or heart disease, confirming flu or COVID early can open the door to antiviral treatment — and those medications work best when started early in the illness. Waiting to see whether it passes can close that window. We’ll cover this properly in Part 5 of this series.
For infants and older adults with RSV, the value of knowing is mostly in monitoring. There’s no antiviral for RSV the way there is for flu, but identifying it tells a provider what to watch for and how closely.
Get emergency care right away if you or someone you’re caring for has:
- Difficulty breathing, shortness of breath at rest, or gasping
- Bluish or grey lips, face, or fingernails
- Chest pain or pressure that doesn’t let up
- Confusion, unusual drowsiness, or difficulty waking
- Signs of dehydration — no urination for many hours, no tears when crying
- A fever in an infant under 3 months old
- In a baby: flaring nostrils, grunting, or the skin pulling in between or under the ribs with each breath
- Symptoms that improve and then suddenly worsen
This list isn’t exhaustive. If something feels seriously wrong, call 911 or go to the nearest emergency room. Don’t wait for a clinic to open.
When to Come See Us
Urgent care is the right fit for the large middle ground — you feel genuinely unwell, you want to know what’s going on, and it isn’t an emergency. Come in if:
- Symptoms are severe or you’re getting worse rather than better
- Fever lasts more than three days, or breaks and then returns
- You have a chronic condition, are pregnant, or are over 65 and have flu-like symptoms
- A cough is producing a lot of mucus, or comes with chest discomfort
- Your throat is severe enough that swallowing is difficult
- You simply want testing to know what you’re dealing with
AG Urgent Care offers COVID-19 testing and RSV testing, and our providers can assess and test for flu and strep throat in the same visit. If a deep cough raises a question of pneumonia, we have digital X-rays on site, so imaging and results happen while you’re here rather than at a second appointment somewhere else.
We’re open seven days a week across five Brooklyn and Queens locations. Walk in, or check in online to hold your spot. If getting out of the house isn’t realistic, a telehealth visit may be an option for some concerns — a provider can advise whether your symptoms need to be seen in person.
Frequently Asked Questions
How can I tell if it’s the flu or just a bad cold?
The most useful clue is how quickly it started. Flu typically comes on abruptly — often within hours — with fever, body aches, and heavy exhaustion. A cold builds gradually over a day or two and usually centers on sneezing, a runny nose, and a sore throat, without much fever in adults. That’s a pattern, not a certainty, and only testing can confirm.
Can I have flu and COVID at the same time?
Yes. Co-infection with two respiratory viruses is uncommon but does happen. It’s one reason a provider may test for more than one thing, particularly if symptoms are severe or aren’t following the course you’d expect.
Do adults get RSV?
Yes. In most healthy adults RSV looks and feels like a bad cold, so it often goes unrecognized. It becomes more serious in adults 65 and older and in people with heart or lung conditions, and it’s a leading cause of hospitalization in infants under one year old.
How long am I contagious?
It varies by illness and by person. With flu, adults are generally most contagious in the first three to four days after symptoms begin, though it can be longer — and longer still in young children and people with weakened immune systems. Colds, COVID, and RSV all have their own timelines. A good general rule is to stay home while you have a fever and for at least 24 hours after it’s gone without fever-reducing medication.
Is it worth getting tested if I feel okay otherwise?
If you’re an otherwise healthy adult with mild symptoms, testing may not change your treatment much. It’s more valuable if you live or work with people at higher risk, if you need documentation, or if you’re in a higher-risk group yourself — in which case an early result can affect whether antiviral treatment is an option.
Coming Up in This Series
Next time we’ll look at this season’s vaccines — what actually changed for 2026–27, who each one is meant for, and how to make sense of a moment when the federal recommendations themselves are unusually unsettled. After that: urgent care versus the ER, the school-season sick cycle in kids, and what higher-risk adults should do differently.
Until then, if something’s going on and you’d rather not guess, come see us. We’re here seven days a week.
Medical Disclaimer: This article is for general informational purposes only and is not medical advice, a diagnosis, or a treatment recommendation. Symptom patterns described here are typical presentations and cannot be used to diagnose any illness — respiratory infections overlap substantially and can present atypically. Always consult a qualified healthcare provider about your own symptoms, especially if you are pregnant, immunocompromised, over 65, caring for an infant, or living with a chronic condition. In a medical emergency, call 911.