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Where are your symptoms worst? Cold, flu or COVID-19? What causes it? How long it lasts What helps When to see a doctor When to get in-person care Can an online doctor help? While travelling Protecting others Conditions How Mobi Doctor works Frequently asked questions Sources
Dr. Chrysoula I. Liakou MD, PhD
- Treated online: Yes, for most colds, flu, sore throats, sinus problems and chest infections. The doctor tells you when you need a test or in-person care.
- Usual course: a cold lasts about 7 to 10 days and flu about a week, but a cough can last three weeks or more.
- Antibiotics: they do not help colds, flu or most coughs, which are viral. They help bacterial infections such as strep throat or pneumonia.
- See a doctor: if you are not improving after a week, a fever lasts more than three days, or you are pregnant, over 65 or have a long-term condition.
- Emergency: call 112 for severe breathlessness, chest pain, blue or grey lips, confusion, or a fever with a rash that does not fade under a glass.
Call 112 or go to an emergency department if you are struggling to breathe or speak, have chest pain, your lips or face turn blue or grey, you become confused or very drowsy, you have a fever with a stiff neck or a rash that does not fade when you press a glass against it, you cough up more than a few streaks of blood, or you cannot swallow your own saliva.
Where are your symptoms worst?
Choose the symptom that bothers you most. Each page covers the usual causes, what helps, and what a doctor can do.
- Blocked or runny noseColds, allergies, nasal sprays
- Sinus pain and pressureSinusitis after a cold
- Mucus in the throatCatarrh and post-nasal drip
- Sore throatViral sore throat or strep
- Swollen, painful tonsilsTonsillitis and quinsy
- Hoarse or lost voiceLaryngitis
- CoughDry, chesty or lasting cough
- Chesty cough with feverChest infection or pneumonia
- Coughing fits for weeksWhooping cough
- Sharp pain when you breathe inPleurisy
- Fever, aches and exhaustionFlu, COVID-19 or RSV
- A high temperatureWhat a fever means
Is it a cold, flu or COVID-19?
A cold builds up over a day or two and mainly affects your nose and throat. Flu comes on within hours, with fever, aching muscles and exhaustion that often put you in bed. COVID-19 can look like either, and only a test tells it apart for sure.
| Symptom | Cold | Flu | COVID-19 |
|---|---|---|---|
| How it starts | Gradually, over a day or two | Suddenly, within hours | Gradually or suddenly |
| Fever | Rare, and mild | Common, often 38°C or higher | Common |
| Aching muscles | Mild, if any | Common, often severe | Common |
| Tiredness | Mild | Severe, and can last weeks | Common, sometimes long-lasting |
| Blocked or runny nose, sneezing | Common | Sometimes | Sometimes |
| Sore throat | Common | Sometimes | Common |
| Cough | Mild to moderate | Common, often dry | Common, often dry |
| Loss of smell or taste | Sometimes, with a blocked nose | Uncommon | Possible, though less common than earlier in the pandemic |
| How long it lasts | About 7 to 10 days | About a week; tiredness and cough can last longer | Usually under two weeks; a few people have symptoms for months |
With recent COVID-19 variants, many people have cold-like symptoms, and some report a hoarse voice or a very painful sore throat. RSV usually feels like a cold in adults, but in people over 75 or with heart or lung disease it can spread to the chest. Flu, COVID-19 and RSV circulate together in winter; to see how much of each is going around where you are, check the flu tracker.
What causes cold and flu symptoms?
Almost all colds, sore throats, coughs and flu-like illnesses are caused by viruses, which the body clears on its own. A smaller number are bacterial, such as strep throat, some sinus infections and pneumonia, and these may need antibiotics. How your symptoms started, how long they have lasted and how unwell you feel point a doctor to the cause.
| What you notice | Usual cause | Read more |
|---|---|---|
| Blocked or runny nose, sneezing and a scratchy throat, building over a day or two | A cold, caused by one of many viruses | Cold |
| Sudden fever, aching muscles, headache and exhaustion | Flu, COVID-19 or another virus | Flu COVID-19 |
| Sore throat with fever and swollen tonsils, without a cough | Possible strep throat, a bacterial infection | Strep throat Tonsillitis |
| Sore throat and fever with a red rash that feels like sandpaper | Scarlet fever, caused by the same bacteria as strep throat | Scarlet fever |
| Facial pain and a blocked nose for more than 10 days, or worse after starting to improve | Sinusitis, sometimes bacterial | Sinusitis |
| Cough with phlegm and a tight chest, without breathlessness | Acute bronchitis, usually viral | Bronchitis |
| Cough with fever, breathlessness or chest pain when breathing in | Possible pneumonia | Pneumonia Chest infection |
| Coughing fits that end in a whoop or being sick, lasting weeks | Whooping cough, a bacterial infection | Whooping cough |
| A hoarse or lost voice during or after a cold | Laryngitis, usually viral | Laryngitis |
| Extreme tiredness, sore throat and swollen neck glands in a teenager or young adult | Glandular fever, caused by the Epstein-Barr virus | Glandular fever |
| Mucus dripping down the back of the throat and a constant need to clear it | Catarrh and post-nasal drip | Catarrh |
| Small white or yellow lumps on the tonsils and bad breath, without a fever | Tonsil stones | Tonsil stones |
How long do colds and flu last, and how long are you contagious?
Most colds last 7 to 10 days, and most people recover from the fever and other symptoms of flu within a week, but a cough can last 2 weeks or more after either. You are most likely to pass flu on in the first 5 days, and a cold can spread from a few days before the symptoms start until they have gone.
| Illness | Usually lasts | Contagious | Work out your dates |
|---|---|---|---|
| Cold | 7 to 10 days; a cough can last up to 3 weeks | From a few days before symptoms start until they have gone, usually 1 to 2 weeks | Cold calculator |
| Flu | About a week; the cough can last 2 weeks or more | Most likely in the first 5 days | Flu calculator |
| COVID-19 | Up to 10 days for most people; tiredness and a cough can last longer | Many people no longer after about 5 days, some for longer | COVID-19 calculator |
| RSV | 1 to 2 weeks | Usually 3 to 8 days | RSV calculator |
| Strep throat | About a week | Until 24 hours after starting antibiotics | Strep throat calculator |
I have been around someone with flu. Will I catch it?
Not necessarily. If you do, symptoms usually start about 2 days after contact, and anywhere from 1 to 4 days. Washing your hands often, not touching your eyes and nose, and not sharing towels lower the risk. If you are at higher risk of complications, speak to a doctor as soon as symptoms start, because antiviral medicine works best when it is started early.
What helps a cold or flu
For most colds and flu-like illnesses, these steps ease the symptoms while your body clears the virus. They are also what a doctor usually suggests first.
- Rest and drink enough Rest while you have a fever, and drink enough that your urine stays pale. It is fine to eat little for a few days.
- Ease the fever and aches Paracetamol or ibuprofen lowers a fever and eases aches and a sore throat. Ibuprofen does not suit everyone, including people with a stomach ulcer, kidney problems or heart failure.
- Soothe the throat and cough Honey in warm water, warm drinks and throat lozenges ease a sore throat and cough in adults. Pharmacy cough medicines help a little at best.
- Clear a blocked nose Saline sprays and steam help. A decongestant nasal spray works quickly, but use it for no more than about seven days, because longer use makes the blockage worse.
Combined cold and flu remedies often contain paracetamol, so check the label to avoid taking a double dose. Vitamin C, echinacea and garlic supplements have little evidence that they prevent colds or speed up recovery.
Do you need antibiotics?
Usually not. Antibiotics only work against bacteria, so they do not help colds, flu, COVID-19 or most sore throats and coughs, and they can cause side effects such as diarrhoea and thrush. They help when a bacterial infection is likely, such as strep throat, pneumonia, whooping cough or sinusitis that has lasted more than 10 days without improving. Green or yellow mucus on its own does not mean you need them.
Antiviral medicines for flu and COVID-19
An antiviral medicine can shorten flu and lower the risk of complications when it starts within 48 hours of the first symptoms. It is mainly for people at higher risk, such as those over 65, anyone who is pregnant and people with a long-term heart, lung, kidney or immune condition. For COVID-19, antivirals are for people at the highest risk of severe illness and must start within five days of the first symptoms. The doctor checks whether you qualify and whether the medicine is safe with your other treatments.
When should I see a doctor about a cold or flu?
Book a consultation if:
- your symptoms are not improving after a week, or get worse after you started to feel better
- a fever lasts more than three days, or comes back after it had settled
- a cough lasts more than three weeks
- a sore throat comes with a fever and swollen tonsils but no cough
- you are pregnant, over 65, or have a long-term condition such as diabetes, asthma, COPD, heart or kidney disease, or a weakened immune system
- you want to know which medicines are safe with your other treatments
When to get in-person care
Call 112 or go to an emergency department now for:
- severe breathlessness, struggling to speak, or lips or a face that turn blue or grey
- chest pain or tightness
- confusion, unusual drowsiness or being hard to wake
- a fever with a stiff neck and a severe headache, or with a rash that does not fade when you press a glass against it
- coughing up more than a few streaks of blood
- drooling, being unable to swallow your own saliva, or a high-pitched noise when breathing in
- severe pain on one side of the throat with difficulty opening your mouth or a muffled voice
Get medical advice the same day for:
- breathlessness on mild exertion, or a fever that comes back after you had improved
- being unable to keep fluids down, or passing very little urine
- getting worse rather than better if you are pregnant, over 65 or have a weakened immune system
- a fever during or after a trip to the tropics
Mobi Doctor consultations are for adults aged 18 and over. A child who is unwell needs a paediatrician or a local doctor in person, and emergency signs in a child mean 112.
Can an online doctor treat colds and flu?
Yes, for most colds, flu, sore throats, sinus problems and chest infections. They are assessed mainly from your story and from what the doctor sees on camera: the doctor asks how it started, watches your breathing, checks the warning signs and can look at your throat. Tests, chest X-rays and examinations that need a stethoscope happen in person, and the doctor tells you when you need them.
What the doctor can do online
The doctor listens, looks at any photos you share and decides with you what helps. If a medicine is the right answer, the doctor prescribes it. If you need an examination, a test or urgent care, the doctor tells you where to go.
- Warning signs checked first Breathlessness, chest pain, dehydration and the signs of pneumonia, quinsy or sepsis are checked first, and you are sent to the right care if any is likely.
- Virus or bacteria The doctor uses the pattern of your symptoms, and validated scores for sore throats, to decide whether antibiotics would help, so you do not take them when they cannot.
- Treatment that suits you Before suggesting any medicine, the doctor asks about pregnancy, your other medicines and conditions such as asthma, kidney or heart disease.
- A plan for the days ahead What to expect day by day, when you should be better, and which signs mean you should be seen in person.
Not sure what is behind your symptoms? A doctor can tell you in one consultation.
See available times →Colds and flu while travelling in Europe
Falling ill abroad changes the practical side, not the medicine. A cold or flu runs the same course wherever you are, but a few things work differently.
- Pharmacies: in most EU countries, paracetamol, ibuprofen and cold remedies are sold only in pharmacies, and the pharmacist can advise on minor symptoms. Every area has a duty pharmacy that opens at night and on holidays, usually listed on the door of the nearest pharmacy.
- Medicine names: the same medicine is sold under different brand names from country to country, so ask for it by its ingredient, such as paracetamol or ibuprofen.
- Flying with a cold: a blocked nose can make your ears hurt as the plane descends. Swallowing, yawning or a decongestant nasal spray shortly before landing helps. With flu or a high fever, wait until you feel better before flying.
- In Spain: our medical reviewer Dr Liakou also edits a Spanish-language flu guide, SíntomasGripe, with the vaccination dates for every comunidad autónoma.
- Emergencies: 112 works in every EU country, free of charge, from any phone.
Protecting yourself and others
Colds, flu, COVID-19 and RSV spread through droplets in the air and on hands, and germs from coughs and sneezes can live on hands and surfaces for 24 hours. Washing your hands, covering coughs and sneezes, and staying at home while you have a fever cut the risk of passing them on. How long you stay contagious depends on the virus: the contagious calculator works it out from the day your symptoms started.
Vaccines prevent the most serious illness. A yearly flu vaccine is recommended for people over 65, anyone who is pregnant, people with long-term conditions and health and care workers, and a COVID-19 booster is offered to similar groups each autumn. RSV vaccines protect older adults, and a whooping cough vaccine in pregnancy protects the newborn baby. A pharmacist or your local doctor can tell you which vaccines you are offered.
How serious is flu?
Flu is more than a heavy cold. Worldwide, it causes around a billion cases a year, 3 to 5 million of them severe, and 290,000 to 650,000 deaths from respiratory illness. The UK Health Security Agency counted around 8,000 deaths associated with flu in the 2024 to 2025 winter, up from about 3,500 the winter before, and found that the vaccine cut hospital admissions by almost 40% in people aged 65 and over who had it.
The flu vaccine: what to know
The injected flu vaccine cannot give you flu, because it contains no live virus, and it takes up to 14 days to work. Side effects such as a sore arm, a slightly raised temperature and aching usually get better within 1 to 2 days. If you have a high temperature, wait until you feel better before having it. The flu vaccine does not prevent colds, and you can still catch flu after it, but the illness is likely to be milder and shorter.
Cold, flu and chest conditions
Most of these can be assessed and treated online. Each page covers the symptoms, causes and treatment, and the signs that need in-person care.
Colds, flu and viruses
- ColdA blocked nose, a sore throat and what actually helps
- FluFever and aches, and who benefits from antivirals
- COVID-19Symptoms, testing, antivirals and long COVID
- RSVA cold-like virus that can hit older adults hard
- Viral infectionHow long viruses last and when to worry
- FeverWhat a temperature means and when to act
- Glandular feverWeeks of tiredness, a sore throat and swollen glands
Nose, sinuses and throat
- Nasal congestionA blocked or runny nose and the sprays that help
- SinusitisFacial pain after a cold, and when antibiotics help
- Catarrh and post-nasal dripMucus at the back of the throat that will not clear
- Sore throatViral or strep, and how to ease it
- Strep throatThe bacterial sore throat that antibiotics treat
- Scarlet feverA sore throat and fever with a sandpaper rash
- TonsillitisSwollen tonsils, quinsy and treatment
- Tonsil stonesWhite lumps on the tonsils and bad breath
- LaryngitisA hoarse or lost voice
Chest and breathing
- CoughDry, chesty or lasting coughs
- Chest infectionBronchitis or pneumonia, and when antibiotics help
- BronchitisA chesty cough that can last three weeks
- PneumoniaA lung infection, including walking pneumonia
- PleurisySharp chest pain when you breathe in
- Whooping coughCoughing fits that last for weeks
- Respiratory tract infectionUpper and lower airway infections explained
- BronchiectasisFlare-ups of a diagnosed lung condition
Chest pain and heartbeat
How Mobi Doctor works
- Book a time that suits you: daily 7am–11pm CET. You can see a doctor over video, usually within 15 minutes. No subscription, and the exact price is shown before you pay.
- Speak to a licensed doctor about your symptoms: describe how your illness started and, if asked, show your throat on camera or take your temperature so the doctor can see how you are.
- Leave with a plan: what to do, what to take and for how long, and which signs mean you should be seen in person. If the doctor prescribes, use the prescription at a pharmacy near you.
No sign-up needed
Frequently asked questions about colds and flu
What is the difference between a cold and flu?
A cold comes on gradually and mainly affects the nose and throat, with sneezing, a blocked or runny nose and a scratchy throat. Flu starts suddenly, with fever, aching muscles, headache and exhaustion that often put you in bed for several days. Most people with a cold keep going; most people with flu cannot. COVID-19 can look like either, so only a test tells it apart.
How long does a cold or flu last?
Most colds last about 7 to 10 days. Most people recover from the fever and other symptoms of flu within a week, but the tiredness and cough can continue for one to two weeks more, and a cough after either can last three weeks or more. See a doctor if you are not improving after a week, or get worse after starting to feel better.
How long am I contagious with a cold or flu?
A cold spreads most in the first two to three days of symptoms. With flu, adults are usually contagious from about a day before symptoms start until 5 to 7 days after. With COVID-19, many people are no longer contagious after about five days, but some stay contagious for longer. The contagious calculator on Mobi Doctor works out your likely contagious period from the day your symptoms started.
I have been around someone with flu. Will I get it?
Not necessarily. If you catch it, symptoms usually start about 2 days after contact, and anywhere from 1 to 4 days. Wash your hands often and avoid touching your eyes and nose. If you are pregnant, over 65 or have a long-term condition, speak to a doctor as soon as symptoms start, because antiviral medicine works best when it is started early.
Do I need antibiotics for a cold or flu?
No. Colds and flu are caused by viruses, and antibiotics only work against bacteria, so they do not shorten the illness. A doctor prescribes antibiotics only when a bacterial infection is likely, such as strep throat, pneumonia or sinusitis that has lasted more than 10 days without improving. For flu, an antiviral medicine can help people at higher risk if it starts within 48 hours of the first symptoms.
What is the best medicine for a cold or flu?
Paracetamol or ibuprofen eases a fever, aches and a sore throat. Honey, warm drinks and lozenges soothe a sore throat and cough, and a saline or decongestant nasal spray helps a blocked nose for a few days. Combined cold and flu remedies often contain paracetamol, so check the label so you do not take it twice. Antiviral medicines help some people with flu or COVID-19 and need a prescription after a consultation.
Can you get rid of flu in 24 hours?
No. Flu runs its course, and most people recover within a week. Rest, plenty of fluids and paracetamol or ibuprofen ease the fever and aches while it does. For people at higher risk, an antiviral medicine started within 48 hours of the first symptoms can shorten flu and lower the risk of complications.
Can I have the flu jab if I have a cold?
If you have a high temperature, wait until you feel better before having the flu vaccine. The vaccine cannot give you flu, takes up to 14 days to work, and does not protect against colds.
Is it a cold, flu or COVID-19?
The symptoms overlap, so you cannot always tell. Sudden fever and aching muscles point to flu, and a blocked nose and sneezing to a cold, while COVID-19 can cause either pattern. A home COVID-19 test taken when symptoms start, and repeated a day or two later if it is negative, answers the COVID-19 question. A doctor can help if you are at higher risk and might need antiviral treatment.
Can I fly with a cold or flu?
Usually yes with a mild cold, though a blocked nose can make your ears painful as the plane descends; swallowing, yawning or a decongestant nasal spray shortly before landing helps. With flu or a high fever, it is better to wait until you feel better, for your own recovery and to avoid passing it on. If you are short of breath, do not fly, and get medical advice.
When should I worry about a cough?
See a doctor if a cough lasts more than three weeks, comes with a fever that does not settle, or makes you breathless. Call 112 or go to an emergency department if you are struggling to breathe, have chest pain, cough up more than a few streaks of blood, or your lips turn blue or grey.
Can an online doctor prescribe treatment for a cold or flu?
Yes, when treatment is right for you. After a video consultation the doctor can prescribe medicines such as antibiotics for a bacterial infection, or antiviral treatment for flu or COVID-19 if you qualify, and you can use the prescription at a pharmacy near you. Most colds and flu need advice and symptom relief rather than a prescription. Codeine cough medicines and other controlled medicines are not prescribed through online consultations.
- Cough (acute): antimicrobial prescribing (NG120), NICE, National Institute for Health and Care Excellence, 2019.
- Sore throat (acute): antimicrobial prescribing (NG84), NICE, 2018.
- Sinusitis (acute): antimicrobial prescribing (NG79), NICE, 2017.
- Pneumonia: diagnosis and management (NG250), NICE, 2025.
- Seasonal influenza, ECDC, European Centre for Disease Prevention and Control.
- Influenza (seasonal) fact sheet, WHO, World Health Organization, 28 February 2025.
- Nirmatrelvir with ritonavir: European public assessment report, European Medicines Agency.
- Flu, NHS, National Health Service (UK), reviewed 3 February 2026.
- Common cold, NHS, National Health Service (UK), reviewed 22 March 2024.
- Flu vaccine, NHS, National Health Service (UK), reviewed 29 September 2026.
- Do I have flu, COVID-19 or a cold? Know the signs and symptoms, UK Health Security Agency blog, 8 October 2025, updated September 2026.
- Coronavirus disease (COVID-19) fact sheet, WHO, World Health Organization, 27 November 2025.
- COVID-19 symptoms and what to do, NHS, National Health Service (UK), reviewed 21 March 2023.
- Respiratory syncytial virus: the green book, chapter 27a, UK Health Security Agency, updated 3 June 2026.
- Respiratory syncytial virus (RSV), NHS, National Health Service (UK), reviewed 5 July 2024.
- Strep A, NHS, National Health Service (UK), reviewed 7 January 2026.
This page is for information only and is not a substitute for a medical consultation. Guideline links are provided for transparency; treatment decisions are made with your doctor.
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