Covid, flu and respiratory syncytial virus (RSV) combine to create a national wave of respiratory illness.
According to data from the Department of Health and Human Services, about 76% of hospital beds in US hospitals are full. Pediatric beds are at a similar level, though six states have 90% or more of their pediatric beds full, according to an NBC News analysis of HHS data.
Covid, flu, and RSV can be difficult to distinguish because they share many common symptoms. But it’s helpful to know which virus you have because that determines what treatments you should receive and how long you should isolate.
Certain characteristics — symptoms or how the disease progresses — can help distinguish each virus. Here are five factors to consider.
Some symptoms are unique to certain viruses
A runny nose, cough, stuffy nose or sore throat can be caused by one of the three viruses or by the common cold. But loss of taste and smell is more commonly associated with Covid than flu or RSV. And wheezing is often a telltale sign of a serious RSV infection, usually found in children or older adults.
The only way to know for sure is to get tested.
“I don’t think anyone would ever say, ‘Hey, listen, I think you have a virus based on your symptoms,’ and dare to say what virus that is,” said Dr. Frank Esper, a specialist in childhood infectious diseases. at the Cleveland Clinic.
Do the symptoms come on gradually or suddenly?
Flu symptoms develop faster than those of Covid or RSV.
“Influenza classically comes on with an abrupt fever at first that happens quite quickly. That’s somewhat in contrast to RSV and Covid, where we think of a slow escalation of symptoms,” said Dr. Scott Roberts, infectious disease specialist at Yale Medicine.
How long has it been since exposure?
The diseases have different incubation times – the time between exposure and symptoms. On average, flu symptoms usually develop two days after exposure to the virus, while RSV symptoms take about four to six days to appear, and the typical incubation period of Covid is three to four days for the omicron variant.
“If I go to a party and get symptoms the next day, it’s probably the flu, because that can be an incubation period of just 24 hours,” Roberts said.
Age makes a big difference in the symptoms and severity of an illness
RSV is unlikely to make a healthy adult very sick, while Covid and flu certainly can.
“In general, if you’re a young, healthy adult or not extremely old, and you get pretty seriously ill, it’s probably not RSV,” Roberts said.
The groups most vulnerable to serious RSV infections are infants, children with lung disease, adults age 65 and older, and people with weakened immune systems.
Symptoms can also look different depending on your age and immune status. Many children will experience respiratory viruses for the first time this year as they return to regular schooling and socializing, so their bodies may have a harder time clearing the infection, which can lead to more extensive symptoms.
According to Esper, nearly one-fourth of children have gastrointestinal symptoms (such as diarrhea, abdominal pain or vomiting) due to viral infections. This is less common in adults with seasonal flu or RSV.
People with weakened immune systems, meanwhile, are more likely to develop severe symptoms or pneumonia from one of the three viruses.
Consider which virus is most circulating in your community
Disease experts expect the number of Covid cases to rise over the holiday season as more people travel and congregate indoors. The average number of daily cases reported to the Centers for Disease Control and Prevention has already risen nearly 11% in the past two weeks, according to the NBC News count.
But it’s difficult to determine local transmission levels of Covid as many people use home tests. RSV and flu tests, on the other hand, are performed at a doctor’s office or ordered by prescription.
RSV infections appear to be past their peak nationwide. Although the CDC does not keep a national count of RSV cases, the number of positive weekly tests dropped from more than 17,000 in the week ending Nov. 5 to about 9,000 in the week ending Saturday.
On the other hand, flu cases are on the rise. The national share of flu tests that came back positive rose from about 8% in the week ending Oct. 30 to nearly 15% in the week ending Nov. 13. Flu hospitalizations are the highest this time of year for more than a decade.
Esper said he expects the Cleveland Clinic to be “swimming in the flu” in two weeks.
However, the picture varies by region. In the Northeast, Roberts said, “we saw the RSV rise in the last one to two months and it’s actually leveled off — which is great news — and then flu, just in the last few weeks we’re seeing an exponential rise.”
“In the Southeastern US – Georgia, Alabama, Mississippi – they saw more or less the opposite. They saw a wave of flu initially, and now you see RSV starting to catch up,” he added.
Available treatments and vaccines
Unlike Covid and the flu, there are no vaccines or universally prescribed treatments for RSV.
“RSV probably scares me the most because there’s nothing you can do about it and so many young kids haven’t seen it. We’re really seeing record increases in our children’s hospitals,” Roberts said.
To reduce the duration of flu symptoms, doctors usually prescribe Tamiflu or one of three other approved treatments. For some people with Covid, doctors may prescribe Paxlovid.
Dr. Ashish Jha, the White House Covid-19 Response Coordinator, highlighted the benefits of getting flu shots and Covid boosters.
“Right now when we have a lot of flu, still have a fair amount of RSV, still have a good amount of Covid, the single most important thing people need to do is get vaccinated,” Jha said at a briefing on Tuesday. “It keeps you out of the hospital.”