Polio is a serious viral infection that used to be common in the UK and worldwide. It's rare nowadays because it can be prevented with vaccination.
Most people with polio don't have any symptoms and won't know they're infected.
But for some people, the polio virus causes temporary or permanent paralysis, which can be life threatening.
Cases of polio in the UK fell dramatically when routine vaccination was introduced in the mid-1950s.
There hasn't been a case of polio caught in the UK since the mid-80s. But the infection is still found in some parts of the world, and there remains a very small risk it could be brought back to the UK.
There's no cure for polio, so it's important to make sure that you and your children are fully vaccinated against it.
Most people with polio won't have any symptoms and will fight off the infection without even realising they were infected.
A small number of people will experience a flu-like illness 3 to 21 days after they're infected.
Symptoms can include:
These symptoms will usually pass within about a week.
In a small number of cases, the polio virus attacks the nerves in the spine and base of the brain. This can cause paralysis, usually in the legs, that develops over hours or days.
The paralysis isn't usually permanent, and movement will often slowly return over the next few weeks and months.
But some people are left with persistent problems. If the breathing muscles are affected, it can be life threatening.
Although polio often passes quickly without causing any other problems, it can sometimes lead to persistent or lifelong difficulties.
A few people with the infection will have some degree of permanent paralysis, and others may be left with problems that require long-term treatment and support.
These can include:
There's also a chance that someone who's had polio in the past will develop similar symptoms again, or worsening of their existing symptoms, many decades later. This is known as post-polio syndrome.
You can become infected with the polio virus if you come into contact with the poo (faeces) of someone with the infection, or with the droplets launched into the air when they cough or sneeze.
You can also get the infection from food or water that's been contaminated with infected poo or droplets.
If the virus gets into your mouth, it travels to your throat and bowels, where it starts to multiply. In some cases, it can also get into the bloodstream and spread to the nervous system.
The virus can be spread by someone with the infection from about a week before any symptoms develop, until several weeks afterwards. Infected people who don't have any symptoms can still pass polio on to others.
There have been rare cases where polio has been caused by being vaccinated with a live version of the polio virus.
This is no longer a risk in the UK because the vaccine used nowadays contains an inactive version of the virus.
As a result of routine vaccination programmes, polio has been largely wiped out in most parts of the world.
Areas declared polio-free by the World Health Organization (WHO) include Europe, the Americas, the western Pacific region and, most recently, southeast Asia.
But polio is found in some places. It's still a significant problem in Afghanistan, Nigeria and Pakistan, and there's a potential risk of infection in other parts of Africa and some Middle Eastern countries.
You can use the country guide on the Travel Health Pro website to check if there's a risk of getting polio in a country you plan to visit.
There's currently no cure for polio. Treatment focuses on supporting bodily functions and reducing the risk of long-term problems while the body fights off the infection.
This can include bed rest in hospital, painkillers, breathing support and regular stretches or exercises to prevent problems with the muscles and joints.
If you're left with long-term problems as a result of a polio infection, you'll probably need ongoing treatment and support.
This may include physiotherapy to help with any movement problems, devices such as splints and braces to support weak limbs or joints, occupational therapy to help you adapt to any difficulties, and possibly surgery to correct any deformities.
The polio vaccination is offered as part of the NHS routine childhood vaccination programme.
It's given by injection in 5 separate doses. These are normally given at:
If you're planning to travel to a polio-affected country, you should get vaccinated if you've not been fully vaccinated before, or have a booster dose if it's been 10 years or more since your last dose of the vaccine.
Read more about travel vaccinations.
You can also get vaccinated at any point if you haven't been fully vaccinated before, even if you're not travelling somewhere where there's a risk of infection.
If you've had polio in the past and haven't been vaccinated, it's still recommended that you get fully vaccinated.
There are 3 types of polio virus that the vaccine protects against, and people who have had the infection before will only be immune to one of these.
The polio vaccination is usually available for free on the NHS.
As the result of an increase in worldwide cases of polio in early 2014, the WHO issued temporary additional travel recommendations for people visiting countries where polio is found. These are still in place as of July 2018.
Depending on where you intend to travel, what you'll be doing there and how long you're staying for, you may now be advised to have a booster polio vaccination before travelling if you haven't had one in the past 12 months.
Some of the countries where there's risk of infection will require proof of vaccination before you're permitted to travel elsewhere. If you don't have this, you may be given a booster dose before departing.