Croup vs. RSV: How To Tell the Difference

When your child has a cough, it can be hard to tell what you’re dealing with — especially during cold and flu season. Among young children, two common culprits are croup and respiratory syncytial virus infection (RSV).

“Both can make kids cough and feel miserable,” says pediatrician Richard So, MD. “But they’re caused by different things and affect the airways in different ways.”

Understanding those differences can help you know what to expect and when your child may need medical care.

6 key differences between croup and RSV

Both croup and RSV affect the respiratory system and spread easily among children. But there are some key factors that set them apart.

1. What causes them

RSV is a highly contagious virus that spreads through respiratory droplets — little particles of liquid that come out when we cough, sneeze or even just talk. You get it by having close contact with someone who has RSV or touching something that’s been contaminated by their droplets.

“Part of what makes this virus contagious is that it can actually live on surfaces for several hours after it comes out of your body,” Dr. So notes.

Unlike RSV, croup isn’t a single virus. Rather, it’s a condition caused by swelling in the upper airway — and several different viruses can trigger that swelling. The most common is the parainfluenza virus.

To further complicate things, RSV is one of the viruses that can cause croup. That means your child can have RSV and croup at the same time.

2. Cough sounds

RSV causes a lot of mucus. When your child’s body tries to expel that mucus, it makes a deep, wet, rattly-sounding cough.

Croup cough is much drier. And it also has a very specific sound.

“Croup cough is very distinctive,” Dr. So says. “It’s very dry and high-pitched, kind of like a barking seal, and it often gets worse at night.”

3. Other symptoms

With RSV, symptoms often start like a common cold: runny nose, congestion, mild fever and some coughing. But because there are a few different viruses that can cause croup, the symptoms aren’t necessarily as identifiable.

Croup often starts with a runny or stuffy nose, and then the coughing comes on. Your child’s voice may sound raspier than usual, too, if they’re old enough to talk. This is because of airway inflammation.

It’s important to know that RSV and croup can both become severe enough that they can cause breathing problems for kids. (More on that in a moment.)

4. What part of the airway they affect

Croup primarily affects the upper airway, which includes the voice box (larynx) and windpipe (trachea). That swelling causes the distinctive, barky cough and breathing sounds that croup is known for.

But RSV can infect both the upper and lower parts of the respiratory tract. It can also lead to infections deeper in the lungs, which can make breathing even more difficult.

5. Age range they usually affect

Both illnesses most often impact young children. RSV is particularly common in babies under 1 year old. By age 2, most toddlers have been exposed to the virus and are less likely to become severely ill from it.

Croup is most common in kids ages 5 and younger.

“It’s less common in older kids and adults,” Dr. So adds. “That’s partly because as we get older, our airways become larger and better able to handle inflammation.”

6. How severe they can get

Croup cough is noisy and can be scary. But it’s usually mild to moderate in its severity, and it can often be managed at home. It typically resolves in about a week.

“RSV can often seem like a regular cold, too, especially in older children,” Dr. So shares. “But in infants, toddlers and kids with other health issues, it can lead to lower airway infections that require hospital care, especially if it becomes hard for them to breathe.”

In infants and toddlers, RSV is especially likely to cause other lung concerns, like:

• Bronchiolitis, a swelling of the small airways of the lungs
• Pneumonia, inflammation and fluid in the lungs

Around the world, RSV is the top cause of acute respiratory infection that leads to kids needing to be hospitalized. (But RSV immunization is up to 90% effective at preventing hospitalization during babies’ first season of exposure.)

When to see a doctor

Whether your child has croup or RSV, it’s important to keep an eye on their breathing. If they become severe, both conditions can cause:

• Stridor, a harsh, raspy sound when your child breathes in or out
• Intercostal retractions, odd chest movements that make it look like your child’s skin or muscles are being sucked in around their ribs when they breathe

“When their airways are narrowed or blocked, like from mucus or pneumonia, kids’ lungs compensate by breathing faster to try to get more oxygen,” Dr. So explains. “Both of these symptoms are signs that your child needs quick medical attention."

Severe cases of RSV, in particular, can be especially dangerous to infants, whose tiny airways can’t always handle that inflammation and mucus. So, seek immediate medical attention if your baby seems to be working harder to breathe.

For either illness, call your pediatrician or seek care if your child:

• Has trouble breathing, including fast or noisy breathing
• Shows signs of dehydration, like dry mouth or fewer wet diapers
• Has lips, face, or nails that look blue or gray
• Struggles to eat or drink
• Becomes unusually sleepy or less responsive
• Develops a fever of 102 degrees Fahrenheit (38.8 degrees Celsius) or higher

And don’t hesitate to reach out to your pediatrician if their cough worsens over several days or if you have other concerns about how their condition is progressing.

“Most cases of both conditions will improve with supportive care,” Dr. So says. “But it’s always better to ask your doctor when you’re unsure, especially in very young children or if symptoms escalate. It’s never the wrong move to check in with a provider.”