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Cold, Flu or RSV? How to Tell Which Virus You Might Have, From Testing to Symptoms

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Three vaccine bottles - labeled 'RSV,' 'COVID-19' and 'Flu' sit next to a syringe and stethoscope on a medical table.
Bottles of vaccine for influenza, Respiratory Syncytial Virus (RSV) and COVID-19. (Getty Images)

Updated 11:15 a.m., December 13

The 2023-2024 winter respiratory virus season is here. And alongside the latest COVID-19 variant and the return of flu season, RSV is once again on the rise around the Bay Area.

RSV — which stands for Respiratory Syncytial (pronounced “sin-SISH-uhl”) Virus — usually causes “mild, cold-like symptoms,” according to the U.S. Centers for Disease Control and Prevention. But in infants, young children and adults over 60, this respiratory virus can attack a weakened immune system to cause severe sickness, leading to hospitalization and even — in serious cases — death.

People in these age groups and the people who care for them are often warned by their health care providers about the dangers of RSV transmission and offered vaccination against the virus. However, there are a lot of people who may not even know RSV exists, let alone how dangerous it can be to spread it to others accidentally — even if getting infected themselves only means mild symptoms.

Keep reading for what to know about RSV testing, how to spot an RSV infection, incubation periods, and who’s eligible for the new RSV vaccine.

Jump straight to:

How bad is RSV around the Bay Area right now?

In its weekly report, on Dec. 8, the CDC said that the U.S. is “experiencing elevated RSV activity, particularly among young children” — and that there is currently “high overall respiratory illness activity” in California.

The impacts on the state’s hospital capacity are already being felt, and three-quarters of intensive care beds around California are full, according to the CDC.

The WastewaterSCAN project monitors the presence of viruses — including RSV, COVID-19 and the flu — in wastewater across the U.S. Alexandria Boehm, a Stanford professor of civil and environmental engineering, who helps lead the project, provided KQED with the latest snapshot data on Nov. 30, that found RSV “levels are trending up and high,” and that “all sites in the Bay Area are categorized as in the high wastewater category” for the virus. This upward trend indicates that the Bay Area is “headed towards the levels we saw last year”. Levels of flu and COVID are also increasing in local wastewater, said Boehm.

In Santa Clara County, health officials recently warned of a dramatic increase in winter viruses in the county’s wastewater — and an especially sharp rise in RSV levels, which the county’s Deputy Health Officer Dr. Sarah Rudman said had doubled in the month leading up to Thanksgiving.

“That worries me,” Rudman told KQED on Monday, “that especially after this holiday weekend with everyone’s travel and gathering there, we’re going to see even higher levels [afterward].”

Dr. Peter Chin-Hong, an infectious disease specialist at UCSF, said that when it comes to lab testing at his hospital right now, more tests are coming back positive for RSV than for the flu or COVID-19.

What about testing for RSV?

At-home testing for RSV isn’t available in the way it is for COVID-19. The only places you’d typically have access to a formal RSV test are at an urgent care center, the emergency room, or elsewhere in a hospital, Chin-Hong said.

“I think in the future it’d be great to have a home test for COVID, flu and RSV,” he said. “But right now, we just have COVID [testing] at home.”

Chin-Hong acknowledges the downsides of being unable to access an RSV test outside of these clinical settings. “It’s good to know so that you don’t infect the very young and very old, who can have more serious consequences,” he said.

And on that note …

So, what are RSV symptoms? How are they different from COVID-19 or the flu?

RSV, Chin-Hong said, “seems like a cold for most people. But that ‘cold’ infecting somebody under two, or older than 60, can land them in the hospital.”

According to the CDC, the symptoms of RSV infection “usually appear in stages and not all at once,” and can include:

  • Runny nose
  • Decrease in appetite
  • Coughing
  • Sneezing
  • Fever
  • Wheezing

One big exception to this list: In some very young infants with RSV, the CDC said that “the only symptoms may be irritability, decreased activity, and breathing difficulties.”

Wheezing could be the particular symptom that might indicate you’ve got RSV rather than another respiratory virus, Chin-Hong said — although wheezing can still be a symptom of those other viruses, too.

So, if you’re unlikely to get access to an RSV test, how can you tell if what feels like a bad cold is actually RSV — or the flu? Chin-Hong said there are a few things that might help you tell the difference:

The speed and severity of symptoms

Chin-Hong said the onset of symptoms for the flu will be sudden and severe, with fever and muscle pain. “You feel like a garbage truck hits you very suddenly,” he said.

Influenza, which, like RSV (and COVID-19), is already spreading throughout the Bay Area this winter, can cause serious problems even in healthy people of any age. Some people are also at higher risk of developing serious flu-related complications if they get sick, including those aged 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant people and children younger than 5 years.

The CDC estimates that last year’s flu season resulted in as many as 58,000 deaths from flu and up to 650,000 flu hospitalizations. WastewaterSCAN’s Boehm noted, in her team’s latest snapshot, that wastewater levels for influenza are “starting to trend up, which suggests influenza infections are starting to rise in our region,” and that based on last year’s records, “we fully expect the levels to keep increasing.”

If you haven’t already, consider getting your flu shot as soon as possible. Read more from the CDC about what to do if you get the flu.

If your cold symptoms are more progressive, but you’re repeatedly testing negative for COVID-19, seriously consider the possibility that you have RSV.

Or, as Chin-Hong puts it: “If you don’t feel like your whole body is on fire, and it feels like a cold — these days, chances are that it’s going to be RSV.”

The incubation period

RSV has a longer incubation period than COVID-19 or a cold — the amount of time between exposure to the virus and getting sick.

Right now, the latest COVID-19 subvariants have an incubation period of three to five days, and a cold will take 24 to 72 hours to incubate after exposure. But RSV has a longer incubation period of “four to six days,” Chin-Hong said. So, if you know you’ve been exposed to RSV but haven’t gotten sick after a few days, unfortunately, it’s unwise to presume you’ve escaped infection.

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While people infected with RSV are usually contagious for “3 to 8 days,” according to the CDC, they can also “become contagious a day or two before they start showing signs of illness” — similar to those infected with COVID-19.

What should I do if I have RSV but I’m not at higher risk?

If you’re not at higher risk for severe RSV but you’re pretty sure you’ve got it, what now?

Manage your symptoms

The CDC said that antiviral medication is “not routinely recommended” to fight an RSV infection — in contrast to COVID-19, for which the antiviral drug Paxlovid is often prescribed, or for the flu, for which antiviral drugs like Tamiflu can be taken.

more virus-related coverage

Most RSV infections, the agency said, “go away on their own in a week or two.”

So, if you’re an adult who’s not at higher risk for severe RSV, the CDC recommends managing fever and pain symptoms with over-the-counter fever reducers and pain relievers, such as acetaminophen or ibuprofen. It’s also important to drink fluids to prevent getting dehydrated.

Stay home as much as you can

Remember, the big difference between having “just” a cold and having RSV is that if you spread RSV, you’re potentially endangering infants and older people who are at much higher risk from it. The best thing to do is keep away from others as much as possible while you’re sick — especially infants and people aged 60 and older. And “definitely don’t go out if you have a fever,” Chin-Hong said — “that’s probably the highest risk.”

What if you really can’t stay indoors away from others? Then it’s time to wear a well-fitted face covering like an N95 or KN95 mask, Chin-Hong said. By masking, you’ll reduce the risks of spreading the virus to those around you.

Why are younger and older people more at risk from RSV?

There are two age groups at the highest risk for severe disease, hospitalization and death from RSV:

Infants and young children

Every year, as many as 80,000 children under 5 years old are hospitalized in the U.S. because of RSV, according to an estimate from the CDC. Children at the greatest risk from RSV include:

  • Premature infants
  • Infants up to 12 months, especially (6 months and younger)
  • Children younger than 2 years with chronic lung disease or congenital (present from birth) heart disease
  • Children with weakened immune systems
  • Children with neuromuscular disorders.

Part of the danger of RSV is how it can bring on more severe infections, including:

  • Bronchiolitis: when the small airways in the lungs are inflamed
  • Pneumonia: when the lungs are infected.

The CDC said that RSV is “the most common cause of bronchiolitis and pneumonia in children younger than 1 year of age.”

These statistics can seem scary — and RSV does undoubtedly pose a threat to many younger children. But for context, the CDC notes that “almost all children will have had an RSV infection by their second birthday.”

If an infant or young child gets infected with RSV, parents and caregivers can always call their provider’s advice line, added Chin-Hong, who said to watch for red flags, including when a young child is having difficulty feeding or breathing, or is wheezing and lethargic. “Infants with quote-unquote ‘colds’ who have any of those [symptoms] should be brought into the hospital or urgent care or the emergency room for advice,” he said.

People age 60 and older

RSV poses a particular risk to older people because of how our immune systems weaken with age. Every year, between 60,000 and 160,000 older adults in the U.S. are hospitalized with RSV, and as many as 10,000 die from it, The CDC estimates.

In addition to causing more severe infections like bronchiolitis and pneumonia, the virus can also exacerbate existing health conditions — including asthma, chronic obstructive pulmonary disease and congestive heart failure.

Some younger adults are also at higher risk from RSV. These groups include folks with chronic heart or lung disease, weakened immune systems or certain other underlying medical conditions.

When should older adults — or their caregivers — seek medical attention due to a potential RSV infection? Chin-Hong said that one of the main concerns for this age group is developing pneumonia, of which a new shortness of breath can be a symptom. Oxygen levels can also be monitored with an at-home pulse oximeter — if a person’s levels drop below 93%, Chin-Hong said that’s a sign to head to the emergency room.

When RSV means being hospitalized

What does hospitalization actually mean for infants and older adults with severe RSV?

Hospitalization often occurs if the patient is having trouble breathing or has become dehydrated — and once in the hospital, they may require extra oxygen or fluids given through an IV if they can’t eat or drink enough on their own.

A patient might also need to be intubated with a breathing tube inserted through the mouth, and be given mechanical ventilation to help them breathe again. While this sounds scary, hospitalization usually lasts for only a few days “in most of these cases,” according to the CDC.

Who can get the RSV vaccine?

In addition to the general benefits of vaccination against the virus, Chin-Hong notes that “there isn’t any good therapy for RSV” currently — making a preventative vaccine even more important.

In May, the U.S. Food and Drug Administration approved the first RSV vaccine for older adults, and, several months later, approved another one for pregnant people, as well as a separate preventative antibody treatment for infants.

RSV vaccines for these groups are available through health care providers and pharmacies, with the shots covered partly or fully by most health insurance plans.

Adults age 60 and older

The CDC recommends this group “should talk with their health care provider about whether RSV vaccination is right for them.” There is no upper age limit for getting an RSV vaccination, which is given as a single shot. Read more about older adults and the RSV vaccine, and about health insurance coverage for this vaccine.

People between 32 and 36 weeks of pregnancy

Vaccinations for pregnant people are one of two ways that infants can be immunized against RSV — in this case, to pass on the benefits to the fetus. The CDC said that a baby born to a mother who got the RSV vaccine “at least two weeks before delivery” will have protection — and “in most cases,” that baby then won’t require a later RSV immunization. Read more about pregnant people and the RSV vaccine, and about health insurance coverage for this maternal vaccine.

Infants

A preventive antibody — not a vaccine — can also be given directly to a baby after birth if a maternal vaccine isn’t an option. This form of immunization is recommended for children younger than 8 months of age during their first RSV season. In some cases, this immunization is extended to children under 24 months of age “with certain conditions that place them at increased risk for severe RSV disease,” the CDC said. Read more about RSV immunization for infants and young children and about health insurance coverage for this immunization.

KQED’s Sara Hossaini and Lesley McClurg contributed reporting to this story.

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