Cold, flu, RSV and croup all circulate in Fort Collins, Loveland and Timnath from fall through winter, and they often start the same way with a runny nose, a cough and a low-grade fever. Which illness is behind those symptoms changes what to do next, whether that means staying home, calling your pediatrician or coming in.
Flu or cold symptoms can look a lot like RSV and croup in the first day or two, and a few details help you sort them out.
How to tell the difference between flu and cold symptoms
Flu symptoms are typically more intense and begin more abruptly than cold symptoms, and a stuffy or runny nose is more common with a cold. A cold usually builds over a day or two, often starting with a runny nose or mild sore throat.
Flu tends to affect the whole body. Along with fever, though not everyone with flu has one, children often have muscle aches, headache and a tiredness that keeps them on the couch or in bed. Vomiting and diarrhea are more common in children with flu than in adults.
A cold usually clears in about a week. With flu, tiredness and a lingering cough can hang on after other symptoms improve. Because the overlap is so large, a flu test can confirm whether flu is the cause.
RSV symptoms in kids
RSV, short for respiratory syncytial virus, usually looks like a cold at first. RSV symptoms in older children typically include congestion, a runny nose, a dry cough, a low-grade fever, a sore throat, sneezing and headache, and they usually appear in stages rather than all at once.
What changes is the cough and the breathing. RSV can move to a wet or rattly cough, wheezing, fast breathing or visible effort to breathe, and it can progress to a serious lung infection called bronchiolitis.
How RSV risk changes by age
RSV is usually mild in older children and teens, but it can cause serious breathing trouble in infants and children under 2, whose airways are smaller. Very young infants may show only irritability, less activity or trouble breathing.
If your baby is under 12 months and breathing looks hard, with nostrils flaring, the skin between the ribs pulling in or a bluish tint around the lips, go to the emergency room or call 911. Before the season starts, ask your pediatrician about the RSV antibody shot for infants.
How to tell croup from RSV
The cough is often the biggest clue. Croup causes a dry, barking cough that tends to get worse at night, from swelling around the voice box and upper airway, and it often follows a day or two of cold symptoms. RSV causes a wet or rattly cough that reflects congestion lower in the airways.
The breathing sounds differ too. Croup can cause a high-pitched sound when your child breathes in, called stridor, while RSV is more likely to cause wheezing when your child breathes out. Croup is most common between 6 months and 3 years of age. If you can't tell which sound you are hearing, call your pediatrician. Noisy breathing while your child is calm or resting needs emergency care.
Symptom comparison for cold, flu, RSV and croup
| Symptom | Cold | Flu | RSV | Croup |
|---|---|---|---|---|
| Onset | Gradual, over one to two days | Usually sudden, more abrupt than a cold | Gradual, cold-like start that appears in stages | Often follows one to two days of cold symptoms, worse at night |
| Fever | Mild or absent | Common, though not everyone has one | Low-grade in older children, can vary in infants | Mild to moderate |
| Cough | Mild | Dry at first, often persistent and can be severe, usually not barking | Wet or rattly, may progress to wheezing | Dry and barking, worse at night |
| Runny or stuffy nose | Common | Common | Common | Common early on |
| Sore throat | Mild | Common | Common in older children | Mild |
| Body aches | Rare | Strong | Rare | Rare |
| Fatigue | Mild | Significant | Mild in older children | Mild |
| Breathing difficulty | No | No | Possible, especially in infants | Possible, with stridor |
| Stomach symptoms | Rare | More common in children | Rare | Rare |
| Typical duration | About a week | About a week, with tiredness or cough that can linger | One to two weeks | Three to seven days |
| Most affected ages | All ages | All ages, with higher risk in children under 5 | Infants and children under 2 | 6 months to 3 years |
What's circulating in Northern Colorado during fall and winter
Respiratory season in Northern Colorado tends to arrive in two phases. Early fall brings colds. Children return to classrooms after a summer apart, and rhinoviruses move quickly, which means runny noses, mild fevers and disrupted sleep right at the start of the school year.
Flu and RSV usually take over as temperatures drop, and the timing of the peak varies from season to season in Colorado. Local surveillance data for Fort Collins isn't always available in real time, but the Colorado Department of Public Health and Environment tracks statewide flu and RSV activity and updates it weekly during respiratory season. Checking it can show whether flu or RSV is rising before your child gets sick.
When to take your child to the doctor for a cough or respiratory illness
Most colds and mild respiratory illnesses can be managed at home with rest and fluids. The right level of care depends on how your child is breathing, how long symptoms have lasted and your child's age.
Fever in a baby under 3 months
If your baby is under 3 months old and has a rectal temperature of 100.4 degrees or higher, call your pediatrician right away, day or night. Your pediatrician may send you to the emergency room, so don't wait to see whether the fever comes down.
Monitor at home if
- Your child has a cold with no fever or a low-grade fever under 100.4 degrees
- Your child is eating and drinking reasonably well
- Symptoms are improving after the first few days
- Your child is older than 3 months and has no underlying health conditions
If you're not sure whether your child needs to be seen, The Youth Clinic's nurse triage phone line can help you decide.
Call your pediatrician if
- Fever lasts more than 24 hours in a child under 2 or more than three days in a child 2 or older
- Your child's cough is getting worse instead of better after several days
- Your child is not drinking and you are concerned about dehydration
- Symptoms improve and then suddenly worsen, which can signal a secondary infection
Seek urgent care if
- Your child has a barking cough or wheezing but is breathing comfortably
- Your child has flu-like symptoms and you want a rapid flu test to guide treatment
- A fever or cough has lasted longer than expected and you want an answer today
- Waiting for the next primary care appointment does not feel right
Go to the emergency room or call 911 if
- Your child's lips or fingernails are turning blue
- Your child is working hard to breathe, with nostrils flaring or the skin between the ribs pulling in
- You hear high-pitched noisy breathing while your child is calm or resting
- Your child is struggling to breathe and cannot be calmed
- Your child is unresponsive or extremely difficult to wake
For cough, cold and flu care or help with fever in children, Pediatric Urgent Care of Northern Colorado is available when your primary care office is not.
How on-site rapid testing changes the decision
Rapid tests can show whether your child has flu, strep or RSV during the same visit, which shapes the decisions that follow, including treatment, school, childcare and whether other family members need to take precautions. Cold, flu and RSV look alike early on, so symptoms alone often can't settle it.
Pediatric Urgent Care of Northern Colorado tests for all three on-site, with results typically back during the visit. Timing matters for flu too. Antiviral medication works best when started within two days of the first symptoms, which is one reason a same-day result helps when treatment is being considered. You can review the full list of services at PUCNC before you come in.
Why pediatric-specific urgent care matters for respiratory illness
Children's airways and immune responses differ from adults', and RSV, croup and flu can look different depending on a child's age. Pediatric Urgent Care of Northern Colorado sees only children, so the providers checking your child's breathing are trained in pediatric respiratory illness.
PUCNC is the only pediatric-specific urgent care in Northern Colorado open 365 days a year, including evenings, weekends and holidays. It coordinates care with local pediatricians and shares patient records with The Youth Clinic, so the team seeing an established patient on a Saturday evening already has their history. You can check location and hours or review care options before your visit.
Flu vaccine and follow-up care
Everyone 6 months and older should get an annual flu vaccine. If your child hasn't had their flu shot this season, a vaccine appointment or well visit at The Youth Clinic is the right next step. You can schedule an appointment online.
If a cough lingers or your child seems unusually tired after an illness, a sick visit can help sort out whether something else is going on.
Frequently asked questions
Can you have flu and a cold at the same time?
Yes, though it is not common. A rapid test can confirm whether flu or RSV is present, which helps narrow the picture, even though it can't rule out a cold virus at the same time.
How do I know if my child's RSV is getting serious?
Watch for a wetter or more frequent cough, wheezing, or a child too tired to eat or drink. In infants under 12 months, those signs mean your child should be seen right away. Nostrils flaring or skin pulling in between the ribs needs emergency care.
When should I take my child to urgent care for a cough?
Go when a cough is worsening after several days, sounds barky or wheezy, or comes with a fever that is lasting longer than expected. For a baby under 3 months with a fever of 100.4 degrees or higher, call your pediatrician right away.
What is the difference between croup and RSV?
Croup causes a dry, barking cough and high-pitched sound on inhale, typically worse at night. RSV causes a wet, rattly cough and wheezing on exhale. Both can cause breathing difficulty, but the cough sound and timing are different.
Does my child need a flu test, or can I just treat the symptoms?
For most older children, care for mild flu is supportive either way, but a result still helps with school and childcare decisions and with watching for a secondary infection. Testing matters most when your child is under 2, has an underlying condition or may need antiviral medication.
Individual children can present differently, and only a medical evaluation can confirm a diagnosis. This post is for general information and isn't a substitute for medical advice. If something doesn't seem right with your child, walk in or check the live waitlist at Pediatric Urgent Care of Northern Colorado.