Strict measures have been put in place since then, with people being told to self-isolate if they have symptoms of the disease.
But what exactly does "self-isolate" mean and who does it apply to?
Who should self-isolate?
If you are displaying flu-like symptoms, in particular a cough and a high temperature of above 37.8C (100F) - you must stay at home for seven days.
If you live with other people, they should also stay at home for at least 14 days, to avoid spreading the infection outside the home.
After 14 days, anyone in the household who does not have symptoms can return to their normal routine. But, if anyone does get symptoms, they should stay at home for seven days from the day their symptoms start. This may mean they need to stay at home longer than 14 days.
The period of self-isolation for people who live on their own remains at seven days.
People over the age of 70, pregnant women and people with certain health conditions, have been asked to stay at home for the coming months to shield themselves from the virus.
Those with very serious health condition such as cystic fibrosis and cancer will be "largely shielded from social contact" for around 12 weeks, or possibly longer.
What does self-isolating mean?
Self isolating means staying at home and avoiding contact with other people.
You must not go to work, school or visit public areas.
Do not use public transport, like buses, trains, tubes or taxis and do not have visitors to your home.
Ask friends, family members or delivery services to carry our errands, such as getting groceries, medications or other shopping.
People should only go out for exercise once per day and ensure they do not come into contact with people while doing so.
What should I do on day one?
Think about what you are going to need while you are in self-isolation - what food and supplies are you going to need and what medicines will you require?
Talk to your employer, friends and family to ask for their help to access the things you will need.
Many people are now working from home, if you feel well enough your employer may allow you to continue.
People should arrange online shopping deliveries to their homes or get friends and family to drop off food where these are not available.
However, the supplies must be left outside, on your doorstep or in the porch.
The majority of companies offering home delivery now do "contactless" drop-offs to prevent the spread of coronavirus.
What if I live with other people?
Try to separate yourself from other people in your home as the virus can easily be transmitted at close quarters.
Try to keep your bedroom door closed and if you cannot stay in a separate room, aim to keep two metres (three steps) away from the other people in your house.
Sleep alone, if possible.
You should minimise the time you spend in shared spaces and keep them well ventilated.
Make sure everyone follows Government hygiene guidance.
Stay away from vulnerable individuals, such as the elderly and those with underlying health conditions, as much as possible.
Use a separate bathroom if possible, but if this is not available, then regular cleaning is required.
The isolated person should use the bathroom last and clean it thoroughly themselves after use and they must use separate towels, for drying and hand hygiene purposes.
Avoid using the kitchen when others are around, but if this is not possible then wear a facemask.
Take your meals back to your room to eat and use a dishwasher to clean cutlery and crockery, but if a dishwasher is not available then wash them by hand using detergent and warm water and dry them thoroughly, using a separate tea towel.
Avoid sharing household items, such as dishes, glasses, cups, utensils, towels, bedding or other items with other people in your home when you have used them.
I live alone with children, what should I do?
The Government knows that for those living alone with children, it's not possible to follow every single measure outlined here - just follow the advice to the best of your ability.
If a child develops symptoms, they need to stay at home for seven days from the onset of their symptoms.
Am I allowed visitors in my home?
Social distancing guidelines mean nobody should be having visitors to their home, regardless of whether they are self-isolating or not.
What should I do if I have pets?
Try to keep away from your pets, but if this is unavoidable, wash your hands before and after contact.
Can I do laundry as I normally would?
Dirty laundry that has been in contact with a person who is unwell can be washed with other people's items.
Make sure not to shake dirty laundry - this minimises the possibility of dispersing virus through the air.
If you do not have a washing machine, wait a further 72 hours after your seven-day isolation period has ended before taking your laundry to a launderette.
Can I go in my garden?
For those with a garden, it is fine to use the space as long as you keep two metres away from other members of your household.
If possible, they should use the outside area separately.
What should I do with household waste?
Personal waste (such as used tissues) and disposable cleaning cloths can be stored securely within disposable rubbish bags.
These bags should be placed into a second bag, tied securely and kept separate from other waste in the room in which you are self-isolating. Keep aside for at least 72 hours before putting into your usual external household waste bin.
If you test positive, you will be instructed what to do with the waste.
What should I do if I feel unwell during self-isolation?
The Government has said that it will not be testing people who are self-isolating with mild symptoms but if you start to feel ill and get a cough, fever, or experience breathing difficulties, call NHS 111 and tell them you are being asked to self-isolate because of coronavirus.
If you have been given a designated medical contact point you can also contact them for advice and they will talk you through the next steps.
Even if the symptoms seem like mild respiratory symptoms, it is better to call for advice.
What can I do to help myself get better?
Drink water to keep yourself hydrated - you should drink enough during the day so your urine is a pale clear colour.
You can use over-the-counter medications, such as paracetamol, to help with some of your symptoms.
When is it safe to stop self-isolating?
You should remain at home until seven days after the onset of your symptoms.
After seven days, if you feel better and no longer have a high temperature, you can return to your normal routine whilst maintaining social distancing and lockdown guidelines.
If you have not had any signs of improvement and have not already sought medical advice, contact NHS 111 online.
If you have no internet access, call NHS 111.
Coughing may persist for several weeks in some people, despite the coronavirus infection having cleared.
A persistent cough alone does not mean you must continue to self-isolate for more than seven days.
Coronavirus: Everything you need to know: