How long is RSV contagious?

The CDC does: people with RSV are usually contagious for three to eight days, and may be contagious a day or two before symptoms show. Some babies and people with weakened immunity can spread it for four weeks or longer.

RSV, respiratory syncytial virus, is a cold for most people and a chest infection called bronchiolitis for some babies. The people it puts at risk are babies under six months, children born prematurely, adults over 75 and anyone with a weakened immune system or a long-term lung or heart condition, according to the NHS. So the practical question is rarely about you: it is whether a coughing toddler can see a newborn cousin or a grandparent.

Day by day

UK & USA (NHS / CDC) does not publish a day-by-day contagious period for RSV.

Are you contagious before RSV symptoms start?

Probably, for a day or two. The CDC says people with RSV may become contagious a day or two before they start showing signs of illness. Symptoms usually appear four to six days after infection, and they come in stages rather than all at once, which means the first day of a runny nose is not the first contagious day.

The NHS publishes nothing on the point. The Dutch RIVM does, and draws a conclusion from it: because the virus circulates widely in winter and children are contagious before symptoms show, it sees no point in keeping a child off school or nursery. Germany's RKI and the RIVM both give an incubation of two to eight days, typically five, a slightly wider range than the CDC's.

When is RSV most contagious?

Neither the NHS nor the CDC names a peak day for RSV. What the CDC gives is a window: usually contagious for three to eight days, counted from the day or two before symptoms. What the NHS gives is the shape of the illness in babies: bronchiolitis symptoms are usually worst between days 3 and 5. That is a measure of how ill the child is, not of how much virus they are shedding, and the two are not the same thing.

The route is the same as for a cold. RSV is spread in the coughs and sneezes of someone who has it, the NHS says. The CDC adds the detail that matters in a house with a baby: the virus can survive for many hours on hard surfaces such as tables and cot rails, and for shorter periods on soft surfaces such as tissues and hands. The toy a coughing sibling has been holding is one obvious route.

How long does RSV last, and when does it stop being contagious?

For an otherwise healthy person the contagious window closes first. The CDC puts contagiousness at three to eight days; the NHS says the illness often gets better on its own in one or two weeks, and the CDC says a week or two. For babies with bronchiolitis, the NHS says the cough usually gets better in three weeks.

That three-week cough is the one parents worry about. On the CDC's figures, a baby who fell ill three weeks ago is well past the usual eight-day contagious limit, even if the cough is still there. But the exception is real: the CDC says some babies and people with weakened immune systems can continue to spread the virus for four weeks or longer, even after they stop showing symptoms. For those children there is no clean end date, and a cough is not the signal to watch.

Is there a test for RSV, and what does it tell you?

The NHS RSV page does not mention testing, and the CDC's public testing page describes home tests for COVID-19 and flu, not for RSV. Where a test is done, the result confirms which virus is causing the illness and nothing more. The CDC makes the general point plainly: testing does not change how likely you are to catch or spread a respiratory virus.

So a positive RSV result in a baby does not lengthen or shorten the contagious window; it names the cause. The days still count from symptoms.

Treatment, vaccines and contagiousness

The NHS describes no medicine that shortens RSV; it says you can usually look after yourself or your child at home, and antibiotics only work if you have a bacterial infection, which RSV is not. Nothing in the NHS or CDC pages used here says any treatment changes how long you are contagious.

What the NHS does offer is a vaccine for the people RSV harms most: in pregnancy from 28 weeks, to protect the baby after birth, and to adults aged 75 and over, some people aged 65 to 74 with weakened immunity or a long-term lung condition, and people living in a care home for older adults. The vaccine is about protecting the vulnerable person, not about making a sick person less contagious.

Nursery, school and work: does a child with RSV have to stay at home?

The NHS RSV page sets no exclusion period. The UK Health Security Agency's list for schools and nurseries says a child with RSV stays away if they have more than mild symptoms, for example a high temperature, which is the same rule it applies to any respiratory infection. For adults the NHS gives no RSV-specific advice; the CDC's general rule is to return once you have had 24 hours of improving symptoms with no fever and no fever-reducing medicine, then take precautions for five more days.

Across the Channel, the answer is mostly silence. Germany's RKI, France's Ameli and Italy's ISS publish no return rule for RSV. Spain's Catalan health service gives no rule either, only that symptoms last seven to ten days and the cough up to three weeks. The Netherlands is the exception and goes further than the UK: the RIVM says there is no requirement to stay away, because exclusion is not useful when the virus is everywhere in winter and children spread it before symptoms.

Everyday situations: a newborn, grandparents, a shared bed, nursery, a flight

In each case count from the first day of symptoms, and remember that the CDC's window starts a day or two before that.

• A newborn in the house: the NHS says keep newborn babies away from anyone with a cold or the flu, and lists babies under six months and premature babies as those at highest risk. Keep a sibling with RSV symptoms out of the baby's room for the CDC's eight days, and wash your hands before any contact with the baby.
• Grandparents: adults over 75 are on the NHS higher-risk list. Put the visit off until day 8, and until the sick person has been fever-free and improving for 24 hours.
• Sharing a bed, or a bedroom with the baby's cot: RSV spreads in coughs and sneezes and survives for many hours on hard surfaces such as cot rails, the CDC says. Separate rooms for the first week if you can; wipe down rails and toys if you cannot.
• Nursery: the UKHSA rule is that mild symptoms are fine but a high temperature is not. A child who is otherwise well can go in; the Dutch RIVM takes the same view, and adds that keeping children at home does not stop the spread anyway.
• A flight or a family dinner: no NHS or CDC rule covers travel with RSV. Use the CDC's 24-hour threshold, and skip any gathering with a baby under six months or an adult over 75 until day 8.
• A care-home visit: care-home residents are offered the RSV vaccine precisely because they are at risk. Wait until day 8 and until you are fever-free before visiting.

How long is RSV contagious in babies, older adults and people with weakened immunity?

This is the illness where the exception swallows the rule. The CDC says some babies and people with weakened immune systems can continue to spread the virus for four weeks or longer, even after symptoms stop. The NHS gives no figure for either group. The European authorities that do give figures are stark: Germany's RKI says weeks and in some cases months for both young children and immunocompromised people; the Dutch RIVM puts children at up to 28 days and notes that after a transplant, people have been found to shed the virus for about 80 days on average.

No authority says older adults stay contagious for longer. They are on the receiving end: the NHS lists adults over 75 and anyone with a long-term lung or heart condition as at higher risk, and asks anyone with cold symptoms and a heart or lung condition or weakened immunity to seek urgent advice.

Why the official guidance on RSV differs between countries

The striking thing about RSV is how little most authorities say. The NHS page is about who is at risk and who gets the vaccine; it gives no contagious period at all. France's Ameli publishes no window, but the French High Council for Public Health (HCSP) puts contagiousness at three to eight days from symptoms, and Spain's health ministry gives the same three to eight days; Italy's ISS publishes no window. Only the CDC, the RKI and the RIVM put numbers on it, and their numbers do not match: the CDC says three to eight days, the RKI three days typical and eight at the outside, the RIVM ten days typical and twelve at the outside.

The gap is partly about who each document is written for. The RIVM guideline is for public-health professionals and reports measured shedding at its longest: 28 days in children and about 80 days on average after a transplant. The RKI's guide for doctors gives a typical three days with eight at the outside. The CDC page is for the public and gives one usual range, three to eight days. They describe the same virus at different levels of caution.

On rules, the difference is philosophy. The UK keeps a symptom-based nursery rule; the Netherlands says openly that exclusion achieves nothing for RSV; everyone else says nothing. If you are in the UK, the honest position is that the CDC's eight days is the best-documented figure for an ordinary case, and that a baby under six months or an immunosuppressed relative deserves the four-week caution the CDC also publishes.

What the guidance says in six countries

The same illness, six official positions. Where a country publishes nothing, the table says so rather than borrowing a neighbour's number.

How to stop RSV spreading at home

• Wash or wipe down toys and clean surfaces regularly; the NHS puts this first, and the CDC says the virus survives many hours on hard surfaces.
• Wash your hands and your child's hands often, the NHS bronchiolitis page says, and do not touch your eyes, nose or mouth if your hands are not clean.
• Use disposable tissues and throw them away as soon as you have used them.
• Keep newborn babies away from anyone with a cold or the flu, the NHS says, and that includes siblings.
• Do not smoke around a child: the NHS says children who breathe in cigarette smoke have a higher risk of severe bronchiolitis.
• If you are the one who is ill, follow the CDC's five days of precautions after you feel better, especially around anyone over 75 or under six months.

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Other illnesses

Contagious periods for the other illnesses covered by this tool.

This tool gives general information based on published guidance. It does not diagnose you and does not replace advice from a doctor who knows your situation. You choose the illness; we do not work out what you have.