Worried about measles? Here are seven things you need to know
As measles outbreaks spread, knowing the dangers and the symptoms is more important than ever.
- 23 July 2025
- 5 min read
- by Linda Geddes
1. Measles is one of the most contagious viruses on the planet
Measles spreads through the air when an infected person coughs or sneezes and is extremely contagious. For each person who has measles, 12 to 18 other people will be infected, assuming they haven’t been vaccinated.
This makes measles around 12 times more contagious than influenza, six times as contagious as Ebola and twice as contagious as COVID-19 or chickenpox.
Because the virus is airborne, you can catch measles just by being in a room where an infected person has been – even if they left two hours ago.
You can also catch it by touching surfaces that infected droplets have landed on, and then touching your eyes, nose or mouth.
Infected people can spread the virus up to four days before they develop the characteristic rash, and for approximately four days afterwards.
So, it is important to contact your doctor immediately if you suspect that you or your child may have been exposed, both to manage the disease effectively and avoid spreading it to other people.
2. It is making a comeback in many countries – including high-income ones
Before the measles vaccine was introduced in 1963, the virus infected an estimated 30 million people worldwide each year, killing around 2.6 million of them.
Thanks to vaccination, the situation today is much better. But even though the proportion of children receiving measles vaccines has increased substantially worldwide in recent decades, immunisation rates have stagnated in recent years and measles remains a significant global threat.
Worldwide, 359,590 measles cases were reported to WHO during 2024 – the second highest this decade, after 2019.
Since January 2025, Yemen, Pakistan and India have recorded the highest number of cases – but Canada ranks ninth globally, with 3,053 cases reported from December 2024 to May 2025.
WHO’s European region has also recorded its highest number of measles cases since 1997, with 127,350 cases reported during 2024 – double that number for 2023.
“Measles is back, and it’s a wake-up call,” said Dr Hans Henri P. Kluge, WHO Regional Director for Europe. “Without high vaccination rates, there is no health security.”
3. Symptoms usually appear seven to 14 days after exposure and follow a characteristic pattern
Measles symptoms usually start with a high fever, cough, runny nose and red, watery eyes.
A few days later, the virus reveals one of its telltale signs: tiny white spots dotting the inside of the cheek.
Then, on around days three to five of the illness, the characteristic rash appears – often beginning at the hairline as flat red patches, which creep down the face, neck, torso and limbs, before reaching the hands and feet.
The rash may be harder to see on black or brown skin, appearing as a darker brown, purple, or dusky colour, but it is usually rough and raised.
As it spreads, the spots can merge into larger blotches with raised bumps on top. This is also often when the fever peaks, sometimes spiking to over 40°C (104°F). The rash usually lasts five to six days before fading.
4. Measles is a serious disease that can have lasting consequences
While measles can pose a risk to anyone, it is particularly dangerous for young children – especially those under five who haven’t been vaccinated.
At this age their immune systems and organs are still developing, leaving them more vulnerable not just to the infection itself, but to the serious complications that can follow.
In 2023, more than half of children who caught measles in Europe had to go to hospital.
Complications can include ear infections, diarrhoea or pneumonia, which can be especially risky for young children. Pneumonia affects up to 6 in every 100 children who catch measles in wealthier countries.
Brain inflammation is another serious complication. This can cause a coma, or trigger lasting deafness or intellectual disability. In rare cases it can be fatal.
Although deaths are relatively rare, they still happen. In the US, up to 2 in every 1,000 children who catch measles will die. In lower income countries, it is closer to 30 to 60 in every 1,000 children.
Even after a person recovers, the risk of complications persists.
Measles is a leading cause of blindness in children living in countries where the virus continues to circulate.
Mounting evidence suggests that the virus may also erase parts of the body’s immune memory for previous infections and vaccinations, heightening survivors’ risk of future infections.
5. Measles can also be risky for adults
Although measles is often considered a childhood illness, the virus doesn't discriminate by age.
In some outbreaks, adults account for up a fifth of cases – and when they catch it the consequences can be severe. Those most at risk of severe complications include people with weakened immune systems and pregnant women.
Infection during pregnancy has been linked to miscarriage, stillbirth, premature birth and babies born with low birthweight.
6. Vaccines are highly effective and safe
Millions of people are immunised against measles around the world each year, and the safety and efficacy of these vaccines has been extensively studied.
Measles vaccines are extremely effective, with a single dose providing up to 93% protection and two doses more than 97% protection against measles, usually for life.
Although a small proportion of people will experience side-effects, these are usually limited to soreness or redness at the injection site, a mild fever and temporary joint pain or stiffness.
Because signs of autism often emerge around the same age children receive the vaccine, it is understandable that some parents may worry about a connection. However, extensive, high-quality scientific studies over several decades have consistently found no link.
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7. Vaccines also shield those who can’t take them
While measles-containing vaccines are safe for most people, because they contain a live weakened version of the virus, they are not suitable for everyone.
People who are pregnant, have a weakened immune system or have had a serious allergic reaction to any ingredients in the vaccine cannot take it.
A first dose is also not usually given to infants until they are 9 months old in countries where measles is common, and 12 to 15 months in other countries.
If you can get vaccinated, ensuring you are up to date with these vaccinations can help to keep these individuals safe.
But because measles is so contagious, a very large proportion of the population (around 95%) needs to be fully vaccinated to achieve herd immunity, which means those who can’t be vaccinated, or don’t fully respond to the vaccine, are protected.
This is why routine immunisation, catch-up campaigns and efforts to counter misinformation are so important.
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