How long is COVID contagious?

The NHS rule follows: stay at home for five days after a positive test, three for under-18s, and avoid people at higher risk for ten. The NHS gives no day-by-day contagious window.

The NHS tells you what to do, counted from the day of your test; the UKHSA and the CDC explain why, based on how long infectious virus is found. The CDC adds what is known about the days before symptoms and about test results, and six European countries now give six different answers to the same question.

COVID contagious period, day by day

Counting the day symptoms start as day 0, this is how the UK (NHS, with CDC figures) figures fall.

COVID incubation period: are you contagious before symptoms start?

Yes, and this is where COVID-19 differs most from a cold. The CDC's background document to its respiratory-virus guidance says the highest levels of live, culturable virus typically occur within a few days before and after symptoms start, and that over half of community transmission is estimated to come from people who have no symptoms at the time. Neither the NHS nor the UKHSA publishes a pre-symptom figure; the UKHSA counts the infectious period from the start of the infection, not from symptoms.

European authorities that do give a number reach further back than most people expect. The Dutch RIVM says transmission is possible from five days before symptoms; Germany's RKI puts the start of its highest-infectiousness window at three days before. The COVID incubation period is wide too: the RKI gives one to eight days, typically three to four, and the RIVM one to fourteen, typically three to six.

When are you most contagious with COVID? The infectious period

You are most contagious around the first symptoms: the CDC says most transmission, regardless of variant, largely occurs early in the course of illness, with the highest levels of live virus in the few days either side of the first symptoms. The RKI's window of highest infectiousness runs from three days before symptoms to five days after; the RIVM's runs from two days before to three days after. The NHS and UKHSA name no peak, but the five-day stay-at-home rule is built on the same fact: the UKHSA says most people are no longer infectious after five days.

The reason is viral load. The CDC describes its 24-hour rule as addressing the period of greatest infectiousness and highest viral load, which for most people is the first few days of illness. The days you feel worst, and the day or two before, are the ones that matter most for a grandparent or a newborn.

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

Most people with COVID feel better within a few weeks, the NHS says, but it can take longer to recover. The contagious period is shorter: the UKHSA says most people are no longer infectious to others after five days, though some are for up to ten days from the start of the infection; the CDC's background document says most people are no longer infectious after eight to ten days.

So the contagious window usually closes well before recovery does. A cough or tiredness in week three is past the infectious periods published for mild illness, and the CDC says you are likely to be less contagious after your symptoms fully resolve. The exception, in the CDC's words, is people with immunocompromising conditions, who can shed the virus for a long time; people who were seriously ill can also stay contagious for longer.

Germany's RKI adds a useful detail: virus traces can be detected for about eleven days, but that is not the same as being infectious; its own contagiousness figure is about five days.

Can you test positive for COVID and not be contagious?

Yes. A positive test means the virus was detected and you have or recently had an infection, in the CDC's words; it does not measure contagiousness directly, though the CDC says a positive test tends to mean you are more likely to spread the virus at the time you test. The CDC's background document says PCR tests, which detect viral genetic material, can stay positive after people have stopped shedding infectious virus, and that the best indicator of infectious virus is viral culture, not a swab result.

Lateral flow (rapid antigen) tests have the opposite problem. The CDC says their overall sensitivity is relatively low, lower still in people with only mild symptoms, and that significant numbers of false negatives occur early in an infection; the FDA advice it links to is to repeat a negative antigen test 48 hours apart. A negative test, the CDC says, does not rule out infection.

This is why the NHS and UKHSA rules count days from the test rather than waiting for a negative result. A positive lateral flow on day eight does not restart the clock, and a negative one on day two does not end it.

Do COVID antivirals make you less contagious?

No UK authority says COVID antivirals make you less contagious: the NHS treatments page says nothing on contagiousness, and neither does the UKHSA guidance, so the same five-day and ten-day counts apply whether or not you take antivirals. Antibiotics do not help: the NHS says they only work if you have a bacterial infection.

The NHS offers COVID-19 treatments to people at highest risk of becoming seriously ill, aged 12 and over, who have symptoms and a positive test. The medicines it lists are nirmatrelvir plus ritonavir and molnupiravir, and it says they need to be given quickly after symptoms start to work. They are not offered to otherwise healthy adults.

How long to isolate with COVID: work, school and nursery

Isolation is no longer a legal requirement in the UK, but the NHS advice is five days at home: if you test positive, try to stay at home and avoid contact with other people for five days after the day you took the test if you are 18 or over, and for three days if you are under 18. For ten days after the test, avoid meeting people who are more likely to get seriously ill from infections. If you have symptoms but have not tested, stay at home while you have a high temperature or do not feel well enough for your normal activities, and go back when you feel better.

For schools and nurseries the UKHSA exclusion list is looser than the NHS stay-at-home advice: a child stays away if they have more than mild symptoms, for example a high temperature. The UKHSA also asks adults to work from home if they can during the five days. The CDC's rule works from symptoms instead: back to normal activities after at least 24 hours of improving symptoms with no fever and no fever-reducing medicine, then five days of precautions.

The neighbours differ. Germany's BIÖG (formerly BZgA) gives the same advice as for any respiratory infection: three to five days at home and until symptoms improve. France's Ameli says isolation is no longer required. Italy abolished mandatory isolation in August 2023 but still asks you to stay at home while you have symptoms, wear a mask around others, avoid frail, immunosuppressed or pregnant people, and keep out of hospitals and care homes. The Dutch RIVM applies measures only where specifically indicated. Spain's health ministry publishes no rule.

Everyday situations: grandparents, a newborn, a shared bed, the gym, a flight

Count from the day of the positive test, or from the first day of symptoms if you did not test.

• Grandparents or a newborn at home: the NHS ten-day rule exists for exactly this. Avoid people more likely to get seriously ill for ten days after the test. The NHS lists people aged 60 and over, pregnant women and people with a weakened immune system as the people for whom getting urgent advice matters most if symptoms get worse or do not improve.
• Sharing a bed: the CDC says the highest viral load is in the first few days either side of the first symptoms, so separate rooms during the five days matter most. If that is impossible, the UKHSA advice is to ventilate the room, leaving windows open for at least ten minutes after you leave it.
• The gym: inside the NHS five days, no. Between day five and day ten the NHS asks only that you avoid people at higher risk, but the CDC says you may still be able to spread the virus after feeling better, so a crowded class can wait until day ten.
• A flight: the UKHSA asks anyone in their five days to avoid crowded places such as public transport, and to wear a well-fitting face covering with multiple layers or a surgical mask if they must go out. After day five, a mask for the flight covers the CDC's five-day precaution window.
• A family dinner: a dinner within the five days breaks the NHS advice; one with an older or pregnant relative within the ten breaks the ten-day rule. Beyond day ten, the UKHSA says infectiousness has passed for nearly everyone.
• A care-home or hospital visit: the NHS ten-day rule covers residents and patients, who are more likely to get seriously ill. Italy's guidance is blunter: do not visit or work in a hospital or care home while you have symptoms.

How long is COVID contagious in children, older adults and people with weakened immunity?

Shorter in children: the NHS says children and young people tend to be infectious for less time than adults, which is why its stay-at-home advice is three days for under-18s rather than five; the UKHSA gives the same reason for its three-day figure.

People with weakened immunity go the other way. The CDC says people with immunocompromising conditions can shed the virus for a long time, and the RKI and RIVM both say immunocompromised people can remain contagious for longer; none of the three gives a number. If you are immunosuppressed, or care for someone who is, the treating team's advice on precautions overrides the five-day count.

No authority says older adults stay contagious for longer; they are the reason the ten-day rule exists, and the NHS lists people aged 60 and over among those who need urgent advice if symptoms worsen.

Why the official guidance on COVID differs so much between countries

No illness on this site divides Europe more, and the reason is history rather than biology. Every country had mandatory isolation during the pandemic and then dismantled it. The UK replaced law with advice in 2022 and kept the day count: five, three and ten. Germany folded COVID-19 into its general respiratory-infection advice. France declared isolation no longer required. Italy abolished the obligation in August 2023 but kept the behavioural advice. The Netherlands applies measures only where specifically indicated. Spain let the rules lapse without publishing a replacement.

The biology is less contested than the rules suggest. The RKI, the RIVM and the CDC all put peak infectiousness in the days around the first symptoms and the usual end of contagiousness around day five, with a tail to day seven, ten or, in the CDC's phrase, eight to ten. Where they differ is on the start: the RIVM allows five days before symptoms, the RKI three, and the NHS and UKHSA say nothing.

A British day count, a German symptom rule and an Italian mask rule can all be correct at once. The NHS and UKHSA set the frame here, with each point where a European authority says something different flagged.

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 COVID spreading at home

• Wear a well-fitting face covering made with multiple layers, or a surgical mask, when you have to be around other people during your five days, and avoid crowded places such as public transport, the UKHSA says.
• Ventilate rooms you have been in by opening windows and leaving them open for at least ten minutes after you have left the room, also UKHSA advice.
• Keep away from anyone at higher risk for ten days after your test; this is the NHS rule, not a courtesy.
• Once you feel better, the CDC asks for five more days of fresh air, good hygiene, a well-fitting mask, distance or testing around other people.
• Work from home if you can during the five days; if you cannot, the UKHSA says to talk to your employer about options.

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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.