The essentials

RSV (respiratory syncytial virus) is a common winter virus. In most people it feels like a cold and clears up in a week or two. It can be serious for babies under 6 months and for older adults or people with heart or lung disease. Breathing trouble in a baby is an emergency. A nose swab test confirms it, blood tests are rarely needed, and treatment is supportive care. Babies can be protected by a vaccine during pregnancy or an antibody shot, and adults 75 and older (or 50 to 74 at increased risk) by one vaccine dose.

What is RSV, at a glance?

  • What it is: a common respiratory virus that infects the nose, throat, airways and lungs[1]. It usually causes mild, cold-like symptoms, much like the common cold.
  • When: RSV spreads in the fall and winter and usually peaks in December and January[1].
  • How common: most children get RSV by the age of 2[3]. Two to three out of every 100 infants under 3 months are hospitalized with RSV each year[3]. Each year, an estimated 110,000 to 180,000 adults aged 50 and older in the United States are hospitalized because of RSV[4].
  • Key test: a PCR test on a nose swab, alone or as part of a respiratory panel that also checks for flu and COVID-19[8].

What are the symptoms of RSV in babies, children and adults?

Symptoms usually start 4 to 6 days after infection and tend to appear in stages, not all at once[2]: runny nose, congestion, less appetite, cough, sneezing, fever and wheezing[2]. Most infections go away on their own in a week or two[5].

  • Very young babies: the only signs may be irritability, being less active and breathing difficulties[2]. Many infants have no fever. Some have apnea, meaning pauses in breathing that last more than 10 seconds[3].
  • Infants and toddlers with lower airway infection: RSV can cause bronchiolitis (inflammation of the small airways of the lung) or pneumonia[3]. Signs include fast breathing, wheezing, flaring of the nostrils and, in severe cases, a bluish skin color from lack of oxygen[6].
  • Older adults and people with chronic illness: RSV can worsen asthma, COPD and heart failure, and it can cause pneumonia[4]. Severe illness can be fatal for some adults[4].

RSV symptoms are not specific: on symptoms alone, it is hard to tell RSV apart from a cold, the flu or COVID-19[1].

When should I see a doctor for RSV?

When to see a doctor

  • Emergency: call 911 for any breathing problem in an infant[6], pauses in breathing, bluish lips or skin, a child too tired to feed or wake up, or an adult who is very short of breath or confused.
  • Within 24 hours for a baby who drinks much less or has fewer wet diapers, symptoms that keep getting worse[2], a high fever[6], or worsening breathing in someone with asthma, COPD or heart failure.
  • At your next appointment to ask about RSV protection for your baby, your pregnancy, or yourself if you are 50 or older with a chronic condition.

Watch fluids closely in children: RSV can make feeding hard, and dehydration is a common reason for hospital care[3].

How do you catch RSV, and who is at risk of severe illness?

RSV spreads through droplets when an infected person coughs or sneezes, through direct contact, and by touching contaminated surfaces and then your face. People are usually contagious for 3 to 8 days[5].

  • Common Babies under 6 months and premature babies are the group most often hospitalized[1][3].
  • Common Adults 75 and older, and adults living in nursing homes[4].
  • Possible Adults with chronic heart or lung disease, a weakened immune system or certain other conditions[4], and young children with chronic lung disease of prematurity or severe immune problems[10].

How is RSV diagnosed? Tests and how to read them

Mild cold-like illness usually needs no test. Testing is mostly done for severe illness, in hospital, or when the result changes care (for example, to rule out flu that could be treated with an antiviral)[5]. In babies with typical bronchiolitis, the American Academy of Pediatrics advises doctors to base the diagnosis on the history and examination, without routine X-rays or lab tests[7].

  • Rapid antigen test: a quick test on fluid from the nose[6]. It is less reliable in adults and misses many cases: compared with PCR, its pooled sensitivity was 64% in a large review[8]. A negative rapid test does not rule RSV out.
  • PCR (RT-PCR): it detects the virus's genetic material and is the most sensitive test, especially in adults[8]. The usual sample is a nasal or nasopharyngeal swab.
  • Multiplex respiratory panel: one PCR test that looks for RSV, influenza, SARS-CoV-2 and other viruses at once. Its sensitivity for RSV is slightly lower than a single-target PCR (93% in the same review)[8].
  • Pulse oximetry: a clip on the finger or foot measures oxygen saturation; it helps decide whether oxygen is needed[7].

Blood tests do not diagnose RSV. They are used mainly in hospital to look for complications: chest X-rays and blood and urine tests may be done[5]. A complete blood count, C-reactive protein (CRP) or procalcitonin can help the doctor judge whether a bacterial infection has been added on top of the virus.

Fictitious example of results in a 78-year-old adult hospitalized with RSV (United States format)
TestResultReference rangeFlag
RSV RNA, respiratory panel PCR (nasopharyngeal swab)DetectedNot detectedA
Influenza A/B RNA, PCRNot detectedNot detected
SARS-CoV-2 RNA, PCRNot detectedNot detected
White blood cell count8.1 x103/µL4.0-11.0 x103/µL
C-reactive protein2.4 mg/dL<1.0 mg/dLH
Procalcitonin0.07 ng/mL<0.10 ng/mL
  1. "Detected": genetic material of RSV was found in the swab; the panel lists each virus on its own line.
  2. Flu and COVID-19 "Not detected": useful, because flu and COVID-19 have specific antiviral treatments and RSV does not.
  3. Normal white cells, mildly high CRP, low procalcitonin: a pattern that fits a viral infection; it makes an added bacterial infection less likely, but the doctor also weighs the exam and X-ray.
  4. Reference range: the ranges here are examples; the ones printed on your own report are the ones that count.

Respiratory panel, blood count and CRP after an emergency visit? BloodSense explains each line of your complete report in plain words, so you know what was found and what to ask your doctor.

Explain my test results

What follow-up is needed after RSV?

Most people need no follow-up once breathing, eating and drinking are back to normal. Children hospitalized for RSV usually improve with supportive care and go home in a few days[3]. For an adult with COPD, asthma or heart failure, the doctor may check that the usual treatment is working again after the infection. Blood tests are repeated only if they were abnormal.

How is RSV treated?

  • No specific medicine for most people: there is no specific treatment for RSV infection[5]. Antibiotics do not work on the virus[6].
  • At home: enough fluids to prevent dehydration, and over-the-counter medicine for fever or pain if needed. Never give aspirin to children, and do not give cough medicine to children under 4[5]. Ask a pharmacist or doctor which product suits a baby's age.
  • In hospital: supplemental oxygen, fluids through a vein, and suctioning of nasal secretions in infants and children[6]. The most severe cases need help with breathing from a machine[3].
  • What usually does not help in bronchiolitis: the AAP guideline advises against routine albuterol, epinephrine or corticosteroids in previously healthy babies with bronchiolitis[7].

How can RSV be prevented in babies, pregnancy and older adults?

These are the recommendations shown on CDC pages on November 2, 2026.

  • During pregnancy: one dose of the maternal RSV vaccine (Pfizer's Abrysvo, the only one recommended in pregnancy) during weeks 32 through 36, from September through January in most of the continental United States[11]. It is not repeated in a later pregnancy; in that case, the baby gets an antibody instead[11].
  • For babies (antibody shot): an RSV antibody (nirsevimab or clesrovimab) is recommended for infants younger than 8 months born during or entering their first RSV season if the mother was not vaccinated in pregnancy, if her status is unknown, or if the baby was born within 14 days of her vaccination[10]. It is given from October through the end of March in most of the continental United States, ideally before leaving the birth hospital[10]. Most babies do not need both the maternal vaccine and the antibody[10].
  • Second season: nirsevimab is also recommended for some children aged 8 to 19 months at increased risk of severe RSV[10].
  • Adults: a single dose of any FDA-licensed RSV vaccine for all adults 75 and older, and for adults 50 to 74 at increased risk of severe RSV. Adults who already received one dose, even last year, should not get another dose at this time[9].
  • Everyday habits: wash hands often, cover coughs and sneezes, clean shared surfaces, and keep sick people away from young babies[5].

Why the rules seem to change: in 2026, a federal court put on hold a revised childhood immunization schedule and the votes of the vaccine advisory committee taken after June 11, 2025. A June 2025 vote had added clesrovimab, so whether a federal recommendation for clesrovimab still applies became unclear, which could affect insurance coverage; the nirsevimab recommendation remains in effect[12]. Ask your pediatrician, obstetrician or pharmacist which product is offered for your baby.

Questions to ask your doctor

  1. Does my baby need an RSV antibody this season, or is the pregnancy vaccine enough?
  2. Which breathing signs mean we should go to the emergency room?
  3. Is a swab test useful in my case, and would a positive result change treatment?
  4. Am I in the group of adults 50 to 74 for whom an RSV vaccine is recommended?
  5. Should my asthma, COPD or heart failure treatment be adjusted while I am sick?

Frequently asked questions

How long is RSV contagious?

Usually 3 to 8 days[5]. Keep washing hands and stay away from young babies until you are well.

Is RSV just a cold in adults?

For most healthy adults, yes. For adults 75 and older or with heart or lung disease, it can lead to pneumonia or a hospital stay[4].

Do adults need an RSV vaccine every year?

No. At this time CDC recommends a single dose, and adults who already had one should not get another[9].

Is RSV the same as bronchiolitis?

No. Bronchiolitis is an inflammation of the small airways; RSV is its most common cause, but other viruses can cause it too[7].

  1. Centers for Disease Control and Prevention. About RSV. December 30, 2025. cdc.gov (accessed November 2, 2026)
  2. Centers for Disease Control and Prevention. Symptoms of RSV. February 20, 2026. cdc.gov (accessed November 2, 2026)
  3. Centers for Disease Control and Prevention. RSV in infants and young children. February 20, 2026. cdc.gov (accessed November 2, 2026)
  4. Centers for Disease Control and Prevention. RSV in adults. February 20, 2026. cdc.gov (accessed November 2, 2026)
  5. MedlinePlus. Respiratory syncytial virus infections. Last updated May 5, 2025. US National Library of Medicine. medlineplus.gov (accessed November 2, 2026)
  6. MedlinePlus Medical Encyclopedia. Respiratory syncytial virus (RSV). Reviewed January 1, 2026. US National Library of Medicine. medlineplus.gov (accessed November 2, 2026)
  7. Ralston SL, Lieberthal AS, Meissner HC, et al. Clinical practice guideline: the diagnosis, management, and prevention of bronchiolitis. Pediatrics. 2014;134(5):e1474-e1502. doi:10.1542/peds.2014-2742 (accessed November 2, 2026)
  8. Onwuchekwa C, Moreo LM, Menon S, et al. Underascertainment of respiratory syncytial virus infection in adults due to diagnostic testing limitations: a systematic literature review and meta-analysis. J Infect Dis. 2023;228(2):173-184. doi:10.1093/infdis/jiad012 (accessed November 2, 2026)
  9. Centers for Disease Control and Prevention. Clinical guidance for RSV immunizations and vaccines (adult guidance updated February 24, 2026). cdc.gov (accessed November 2, 2026)
  10. Centers for Disease Control and Prevention. RSV immunization guidance for infants and young children. August 18, 2025. cdc.gov (accessed November 2, 2026)
  11. Centers for Disease Control and Prevention. RSV vaccine guidance for pregnant women. December 19, 2025. cdc.gov (accessed November 2, 2026)
  12. Congressional Research Service. Changes to CDC vaccine recommendations in 2025 and 2026. Insight IN12684. April 28, 2026. congress.gov (accessed November 2, 2026)

This page is general information. It does not replace the advice of a doctor, who assesses breathing and hydration and decides on tests, treatment and immunization.