Up to 160,000 Londoners could catch measles in a huge outbreak, health chiefs are warning.
The UK Health Security Agency highlighted modelling showing how the disease could spread very fast through parts of the capital.
The health bosses stressed that there is now a “big measles outbreak” in parts of London mainly affecting unvaccinated children under the age of 10.
The UKHSA said the outbreak in schools and nurseries in north-east London had left some children requiring hospital treatment.
The agency had previously reported 34 laboratory-confirmed measles cases in Enfield from January 1 to February 9.
More than 60 suspected cases of measles have been reported by seven schools and a nursery in Enfield, according to reports.
As the health chiefs urged parents to get their children vaccinated against measles, they warned how an outbreak in the capital could dramatically escalate, based on a risk study carried out in 2023.
The UKHSA assessment found the risk of a measles epidemic across the UK was considered low.
“However, with lower current levels of coverage in London, a measles outbreak of between 40,000 and 160,000 cases could occur in the capital,” it added.
“The risk in London is primarily due to low vaccination rates over several years, further impacted by the COVID-19 pandemic, particularly in some areas and groups where coverage of the first MMR dose at 2 years of age is as low as 69.5%.”
The study emphasised that as more and more people are unvaccinated against measles, the risk of outbreaks was growing over the years.
It also stressed the high risk of cases linked to overseas travel leading to outbreaks in specific population groups such as young people and under-vaccinated communities.
Dr Vanessa Saliba, consultant epidemiologist at the UKHSA, said: “Our latest data shows we are now seeing a big measles outbreak in north-east London, mostly affecting unvaccinated children under 10 in schools and nurseries, with some being hospitalised.
“Measles is a nasty illness for any child, but for some it can lead to long-term complications and tragically death, but is so easily preventable with two doses of the MMRV vaccine.
“If your child has missed any of their doses it’s important to catch up as soon as possible, giving them vital protection against this highly contagious disease, but also helping to protect more vulnerable children around them who are too young or unable to have the vaccine due to a health condition.”
Measles is a highly infectious viral illness that can spread very easily among people who are not fully vaccinated.
While many people recover, the illness can lead to serious complications such as pneumonia, brain inflammation and, in rare cases, long-term disability or death.
Global health officials announced earlier this year the UK is no longer considered to have eliminated measles.
Figures published last August by the UKHSA showed just 64.3% of five-year-olds in Enfield had received both doses of the MMR vaccine in 2024/25, one of the lowest rates in the country.
A message currently posted on the NHS Ordnance Unity Centre For Health GP surgery’s website said there is a “fast-spreading measles outbreak in several schools across Enfield”.
It added: “Infections have been confirmed across at least seven schools in Enfield and Haringey and it is spreading.
“During this recent outbreak, one in five children have been hospitalised due to measles and all of them had not been fully immunised.”
To try to contain the outbreak, pupils could be excluded from schools for up to 21 days if they have come into contact with someone with measles.
Enfield Council said it is “working closely” with the UK Health Security Agency, the NHS and local partners to respond to the confirmed outbreak of measles in the borough.
Alev Cazimoglu, the council’s cabinet member for health and social care, said: “The current outbreak has mainly affected children and some have required additional care with a short stay in hospital.
“Measles is one of the most infectious known diseases. It is approximately six times more infectious than Covid-19.
“Catching the measles is entirely preventable, but it spreads extremely quickly where vaccination levels are low.
“By checking your family’s vaccination status and taking up the free NHS vaccine, you are protecting not only yourselves but also vulnerable members of our community.”
There is no treatment for measles, only the vaccination to prevent catching it, which is part of the measles, mumps, rubella, varicella (MMRV) injection.
Two doses of a measles-containing vaccine provide high levels of protection and help prevent further outbreaks.
