How Long Is COVID Contagious? When It Stops Spreading
Medically Reviewed by Dr. Pedro Yelamo Vera, MD
Licensed Physician No. 484814280 · Official Medical College of Bizkaia (Spain)Last reviewed: 31 October 2026
How long is COVID contagious? When spread peaks, when it falls, why tests stay positive, and what Spain, the UK and the US advise while you are ill.
You don't have to figure this out alone
Dr. Pedro Yelamo Vera is an independent, bilingual GP licensed in Spain. Book a 15-minute video consultation in English or Spanish for €50, with a private electronic prescription issued under Spanish law when clinically appropriate.
How long is COVID contagious? Most people are most contagious from a day or two before symptoms start until a few days after. Studies found no live virus after day 9 of illness. Children tend to be contagious for less time. Spain no longer requires isolation, but advises a mask and care around vulnerable people while you have symptoms.
- Symptoms start 2 to 14 days after contact, most often around day 5.
- You can pass COVID on before you feel ill. Spread peaks around the day symptoms start.
- Spain: no isolation rule. Wear a mask while you have symptoms and keep away from vulnerable people.
- UK: stay home 5 days after a positive test (3 for under-18s). US: stay home until you are fever-free and improving for 24 hours.
- A test can stay positive for weeks after you stop being contagious.
Dr. Pedro Yelamo Vera is a GP licensed in Spain (Colegiado No. 484814280).
For a medical emergency, call 112 or go to the nearest local emergency department. Do not wait for a video consultation or an online reply.
How long does it take for COVID symptoms to start?
MedlinePlus says symptoms may appear 2 to 14 days after contact with the virus. Most people notice them around day 5. Some people never get symptoms at all, but can still spread it.
Common symptoms listed by the NHS include a high temperature, a new cough, a sore throat, a blocked or runny nose, tiredness, aches and a headache. Some people lose their sense of smell or taste.
How long does COVID last?
There is no fixed number. Most people have a mild illness and get better at home. If symptoms last 4 weeks or more, MedlinePlus calls it long COVID. The NHS uses a cut-off of 12 weeks. In Spain you will hear COVID persistente.
When are you most contagious with COVID?
You are most contagious around the day your symptoms start. A study in Nature Medicine found the virus level in the throat was highest at symptom onset. It estimated that 44% of people caught COVID from someone who had no symptoms yet.
So you may have passed it on before you knew you were ill. This is why masks and fresh air help.
When does COVID stop being contagious?
For most people, the risk falls a lot after the first week. A review in The Lancet Microbe found no study that grew live virus after day 9 of illness. These studies were done early in the pandemic, so treat this as a guide, not a rule.
- Children tend to be contagious for less time than adults, says the NHS.
- People with weak immune systems can spread the virus for longer, the CDC notes.
- Feeling better is not a guarantee. The CDC says you may still spread it after you feel well.
Why is my COVID test still positive?
Tests pick up bits of the virus, not only live virus. The same review found these bits stayed in the nose and throat for about 17 days on average, and sometimes much longer. A positive test after your symptoms have gone does not always mean you are still contagious.
COVID or a bad cold that is not getting better?
You can book a video visit with a GP licensed in Spain, in English or Spanish. He goes through your symptoms, checks your risk, and tells you if you need to be seen in person.
Do I need to isolate with COVID in Spain?
No. Spain's Ministry of Health (Ministerio de Sanidad) ended home isolation for most people in 2022. Its strategy that year advised a mask, fewer social contacts and no contact with vulnerable people for 10 days after symptoms began. Close contacts no longer quarantine.
Its newer advice of December 2025 covers all respiratory infections, including flu and COVID. It asks people with symptoms to wear a surgical mask (mascarilla quirúrgica), especially around vulnerable people, and to cut down on social contact.
Hospitals, care homes and some workplaces have their own rules. Ask your employer or school if you are unsure.
How do the UK and US rules compare?
| Country | What to do |
|---|---|
| Spain | No isolation rule. Mask while you have symptoms, fewer contacts, protect vulnerable people. |
| UK (NHS) | Adults: try to stay home 5 days after the test day. Under-18s: 3 days. Avoid high-risk people for 10 days. |
| US (CDC) | Stay home until you have been fever-free without medicine and improving for 24 hours. Then take extra care for 5 days. |
They differ in detail but agree on the main point: stay away from others while you feel ill, and protect people at higher risk.
Who is at higher risk from COVID?
MedlinePlus lists older people and people with conditions such as cancer, COPD, diabetes, heart disease, HIV, obesity, moderate or severe asthma, or a weak immune system. Pregnancy and smoking also raise the risk. If you are in one of these groups, contact a doctor early.
When should you see a doctor today?
- Your symptoms are getting worse, or not getting better.
- A high temperature lasts 5 days or more, or does not come down with paracetamol.
- A baby under 3 months has a temperature of 38°C or more, or a baby aged 3 to 6 months has 39°C or more.
- You are in a higher-risk group, or pregnant.
Call 112 if you are so breathless you cannot say short sentences at rest, or you have chest pain or pressure, blue lips or face, cough up blood, are confused or hard to wake, faint or have a fit, or a rash does not fade when you press a glass on it.
Talking it through with a doctor by video
Dr. Yelamo is a GP licensed in Spain. He sees adults, children and pregnant patients by video, every day from 07:30 to 20:30 (Spain time). In the visit he will:
- Ask when your symptoms started and how they are changing.
- Check your breathing on camera and your risk factors.
- Agree a plan for rest, symptom relief and staying away from others, and tell you if you need to be seen in person.
He does not promise any test or prescription before the visit. Where clinically appropriate, following a genuine evaluation. Treatment and prescriptions are issued solely at the doctor's discretion based on evidence-based clinical guidelines.
A prescription is never guaranteed: it is issued only where clinically appropriate after a genuine evaluation, as a private electronic prescription under Spanish law. This service is for urgent, non-emergency care. In an emergency, call 112.
See how the Urgent Care video visit works. It lasts 15 minutes and costs €50.
This guide is general information. It does not replace a consultation with your doctor.
Frequently asked questions
How long is COVID contagious?
Most people are most contagious from a day or two before symptoms start until a few days after. Studies found no live virus after day 9 of illness. People with weak immune systems can spread it for longer.
Do I have to isolate with COVID in Spain?
No. Spain dropped home isolation for most people in 2022. The Ministry of Health advises a surgical mask while you have symptoms, fewer social contacts, and extra care around vulnerable people.
How long should I stay home with COVID in the UK?
The NHS says adults should try to stay home for 5 days after the day of the test, and under-18s for 3 days. Avoid people at higher risk for 10 days.
Why is my test still positive after a week?
Tests can pick up pieces of the virus for weeks. A review in The Lancet Microbe found these lasted about 17 days on average, while live virus was not found after day 9.
Can my child go to school with COVID?
The NHS says children with mild symptoms, such as a runny nose or mild cough, can go to school if they feel well enough. Keep them home if they have a fever or feel unwell.
When should I call 112 with COVID?
Call 112 for severe breathlessness, chest pain or pressure, blue lips or face, coughing up blood, confusion, fainting or a fit, or a rash that does not fade under a glass.
Sources
- NHS: COVID-19 symptoms and what to do
- CDC: Preventing spread of respiratory viruses when you're sick
- MedlinePlus: COVID-19
- Ministerio de Sanidad: recommendations for acute respiratory infections (Spanish, December 2025)
- Cevik et al., The Lancet Microbe: viral shedding and infectiousness
Related guides
Medical Citations & Sources
This content is written and reviewed by a licensed physician with reference to the following official health authorities.
