Is it a cold, RSV, flu or COVID? Here’s what doctors say about how you tell.

Coughing, sneezing, runny nose: What is it?

Guessing what your child is suffering from may not be that easy.

Fever, muscle aches, headache?

Is it cold, enterovirus, RSV, flu? What’s a parent to do?

Loss of taste and smell? That one we know: It’s COVID-19 for sure.

But with so many bugs around, it’s not easy for parents to know what it is their child is suffering from. And, doctors say, except for COVID and flu, it doesn’t matter that much.

Respiratory syncytial virus

“When people talk about colds and flu, a lot of people use them interchangeably and people say, Oh well, I’ve got the flu,” said Dr. Ian Michelow, head of pediatric infectious diseases and immunology at Connecticut Children’s Medical Center.

“In fact, flu is short for influenza and it’s a specific respiratory viral infection,” he said. “And it’s got implications because it is treated potentially in certain situations.”

Now, respiratory syncytial virus is running rampant, with Yale New Haven Hospital hitting a record 41 patients on Thursday. It can cause wheezing and can be quite serious, but it isn’t the only disease that has wheezing as a symptom, Michelow said.

“RSV, typically, when it starts getting more severe, causes wheezing in the lungs, and that causes an illness called bronchialitis,” he said. “And that is a very common manifestation of RSV. But a child who is wheezing, and a fever, and you think it’s most likely RSV? Well, you may be right, especially now, because there’s an outbreak of RSV everywhere. But it doesn’t necessarily have to be RSV because other viruses can also cause wheezing.”

According to the Centers for Disease Control and Prevention, symptoms of RSV include runny nose, decrease in appetite, coughing, sneezing and fever, in addition to wheezing, so it may be confused with the common cold, which is caused by a rhinovirus or a coronavirus — but not the one that causes COVID.

“What I would emphasize, in my way of thinking about this, is not for people to try to guess exactly what the virus is, but rather to understand that there are many different respiratory viruses that are circulating,” Michelow said.

“Some are more common at certain times, and right now we’ve seen a lot of RSV, but last month and the month before we were seeing a lot of rhinovirus and enterovirus, which can also cause respiratory problems. And it can be pretty severe,” he said.

That’s especially true for a child who has asthma or another respiratory condition, Michelow said.

There is a wide spectrum of most respiratory diseases, from no symptoms at all, to needing to go to the hospital, to needing to be admitted and given breathing support, he said.

“If you were to say, can you distinguish between the various coughs and colds caused by different viruses? You cannot easily and that’s the point,” Michelow said. “If it’s mild, they can look very, very similar. When they start getting more severe, then yes, some of these viruses have more distinctive symptoms and signs.”

Influenza

Flu, for example, “typically causes high fevers. There can be coughing or a sore throat and it can cause muscle aches and pains and headaches,” Michelow said. COVID is tracked by the CDC, but because there are other viruses with similar symptoms to flu, the CDC also tracks “influenza-like illnesses” as a way of determining how prevalent flu is. Those are defined as a fever of 100 degrees or above and a cough or a sore throat, Michelow said.

Flu is “potentially preventable and treatable,” Michelow said, but it caused a record 199 deaths in children in 2019-20, before dropping because schools were shut and people were protecting themselves from COVID.

Michelow and Dr. Scott Roberts, associate medical director for infection prevention at Yale New Haven Hospital, both had a strong message about flu, as well as COVID: Get vaccinated. Those who are will have a milder case if they do get the disease, the doctors said.

There is no vaccine for RSV or other respiratory illnesses, however. As for testing, it is needed to detect COVID, because of how infectious and dangerous it can be. But for public health reasons, hospitals do test for COVID, flu and RSV, according to Roberts.

When it comes to flu, “not everyone needs to go to be tested,” Michelow said. “The ones that really should be tested are those again with underlying medical problems or associated medical problems. Or if you’re living with people who are elderly or have their own medical problems, because you can stop the spread by isolating and by also getting treatment.” Treatment for flu includes the drugs Tamiflu and baloxavir, sold as Xofluza.

Roberts said the various diseases do have differences, such as the incubation period, “the time from when you get exposed to the virus and infected to the time when you start having symptoms.” RSV is an average of five days, but a range of two to eight days. Flu has a range of one to four days, with an average of two. And COVID has a range of two to 14 days, with an average of three.

A cold also tends to have milder symptoms that the other diseases, although they can have mild symptoms too, Roberts said. “COVID, flu and RSV can have a range of symptoms to as minor as the sniffles to as severe as a deep lung pneumonia, requiring oxygen and a mechanical ventilator,” he said.

“So, that’s why we focus on the problem with those three viruses is, they cause really the most severe disease, so we really worry about it,” he said.

Spreading germs

Another difference is how the diseases spread. COVID, the flu and colds spread similarly, by droplets in the air, Roberts said. On the other hand, “RSV spreads much more through touching contaminated surfaces than it does through coughing, sneezing, so … we really focus more on washing hands, cleaning contaminated surfaces with Lysol or something,” he said.

Colds and RSV have neither vaccines nor treatments, outside of painkillers and over-the-counter medications. “When it comes to RSV and other things like enterovirus, it’s not all that important” to know which is which, Roberts said, “because you’re just going to basically treat them the same way,” unless a child becomes seriously ill or has a condition such as asthma.

Because of the surge in cases, “we’re testing now for RSV, certainly, but I think before we did not just because it didn’t change anything,” Roberts said.

He is concerned, however, about what the winter will bring.

“The concern I have is that, first, we don’t know when this RSV surge is going to end,” he said. “And second, what if this continues and then we see COVID and flu come up in higher numbers. Then the hospital gets even more strained. All this is a pretty concerning trend.”

That’s why Roberts promotes the flu vaccine.

“Whatever people can do to mitigate spread of any virus that would require hospital care I think we should do, because the hospitals are so strained,” he said. “The last thing we need right now, on top of the 41 kids with RSV in the children’s hospital, is more and more kids coming in with the flu that takes bed space.”

Ed Stannard can be reached at estannard@courant.com.