Authors: Liz Herrieven / Editor: Nikki Abela / Codes: DP2, IC5, SLO5 / Published: 16/01/2024

Many of us in UK Emergency Medicine, including those of us who have been around a bit (I’m older than I look), will have gone most of our careers without seeing any confirmed cases of measles. Vaccination works, and so measles has been, until recently, something to revise for exams but not really something to consider on the shop floor.

Vaccination rates have been dropping though, and are now at their lowest in 10 years, so measles is back in our departments and has to be in our differential diagnosis list.

What is it?

Measles is a highly contagious disease caused by the measles virus, which is part of the paramyxovirus family (RNA viruses that cause respiratory illnesses). It’s spread through respiratory droplets (aka snot). In fact, it’s so infectious that spending 15 minutes with someone who has the illness is enough to catch it, and the R0 (remember that from COVID-19?) is 15-20, i.e. one person with measles is likely to infect 15-20 others.

The incubation period is between 7-21 days, and the infective period (when it can be passed from one person to another) is from 4 days before the rash develops, to 4 days after. That 4 days before the rash is the tricky bit – preventing spread of infection before you know you have the infection involves contact tracing and knowing who is at risk.

Clinical features

The first features seen are, unfortunately, the same features that most children in most EDs across the country will have at the moment – cough, runny nose and fever. Red and watery eyes are something to watch out for though, and less often seen in other URTIs. Koplik spots are the feature most people will remember from exam revision – but these are difficult to see and are only present transiently (usually 2 or 3 days prior to the rash), so are not always helpful. When they are present, though, these small, red spots, with bluish-white centres, seen on the inside of the cheek, are pathognomonic for measles.

Fig.1 Measles via

The measles rash can look like many other viral rashes – erythematous, blanching, maculopapular, so a mix of raised and flat spots. The thing that makes it different, though, is that it usually starts behind the ears, on the neck or on the face, and spreads down, whereas many others (e.g. Roseola) start on the trunk and spread outwards. The rash lasts about 5 or 6 days before fading, and can go brownish in colour over that time.

Another thing to watch out for, is that most children with measles will look miserable. They are unlikely to be the happy, playing, spotty child at the colouring table, and more likely to be the miserable, clingy, spotty child, with red, watery eyes and an annoying cough.

Fig.2 Koplik spots via

Who might have measles?

Short answer – we need to start thinking anyone might have it, but obviously some will be more likely than others to catch the virus. Risk factors include:

  • Unvaccinated
  • Partially vaccinated – a complete course of MMR is 2 doses – the first is usually given at 12 months old, the second at 3 years 4 months old. One dose is reported to confer 95% protection.
  • Contact with confirmed or highly likely case – someone might present after being informed by UKHSA, for example, that they have been in contact with a known measles case
  • Member of an under-vaccinated community – e.g. refugee community, traveller community
  • Travel to areas where measles is circulating (this may be within the UK, or abroad)
  • Attendance at a mass gathering event
Fig.3 Measles via CDC Public Health Image Library
[You can view another presentation of Measles on the dark skin here].


You’ll need to check with your local labs and ID colleagues, but this is likely to involve either oral swabs, oral fluid, serum samples or a combination. Where I work, we take a virology swab of the buccal mucosa although this changes as the rates change, so do check your local guidance. It also may vary if the patient has been in contact with a vulnerable individual (where accelerated prophylaxis may need to be given), so ask about contacts (this may also mean scanning to see if they sat next to an infant for more than 15 minutes in the waiting room), and talk to the experts if needed.

Notifiable disease

Measles is a notifiable disease so, if you suspect it, you have a duty to report it to the UK Health Security Agency (UKHSA, formerly Public Health and, prior to that, the Health Protection Agency). That sets in motion contact tracing processes, which may vary depending on where you are in the country. Don’t wait for confirmation from the lab (although they will do their own notification if the test is positive) as the earlier cases are identified, the more likely it is that other cases can be prevented. Don’t worry about getting it wrong, either – it’s better to be safe. The exact process for notification will vary, again, across the country, but generally it involves filling in a form, which can be found here.


Most children will need only the usual supportive treatment of oral fluids and analgesia/antipyretics, with good safety netting with regards to possible complications – largely viral pneumonitis, otitis media, diarrhoea and croup. It’s important to also inform parents that their child must isolate until the end of the infectious period (four days after the rash appears). Some might need antibiotics for secondary bacterial infection (generally pneumonia). Those at high risk may need intravenous immunoglobulin after contact with confirmed cases – so don’t forget to confirm diagnosis through testing and notify UKHSA about possible cases.


So, measles is a viral illness, which makes a child feel miserable, but most children can be treated at home with paracetamol, ibuprofen and oral fluids, so why are we bothered? Well, it’s the potential complications. These include otitis media (which can lead to deafness), profuse diarrhoea (with the risk of dehydration), pneumonia (the commonest cause of death in measles), encephalitis (which may lead to convulsions) and subacute sclerosing panencephalitis (SSPE – very rare, slowly evolving and fatal disease of the central nervous system).

Those most at risk of severe measles or related complications include those with immune system compromise, such as those on chemotherapy or long-term steroids, young unvaccinated children, children with complex conditions or comorbidities which put them at greater risk, and pregnant people.

Infection prevention

Many hospitals have alerted triage nurses to isolate potential measles cases from the front door. This makes it easier to contact trace without having to go through the whole waiting room for a confirmed case.

For staff going into isolated cases, it’s time to get fit-tested again, I’m afraid. An FFP3 mask is needed, along with gloves and apron and plenty of handwashing, to help prevent spread of measles and to protect yourself and your patients. It’s also important to make sure you’re immune to measles, either through vaccination or previous infection. Those of us born before 1988 (I know, again, I’m older than I look) will not have received the MMR as part of the UK childhood vaccination schedule, and those born after may have been affected by misinformation about the vaccine. Those born in other countries may have been through different vaccination programmes. If you’re not sure, ask Occupational Health to check your immunity.

Measles in Adults

Of course, there are plenty of cases of measles in adults too, and these are probably the ones that worry you more as adult clinicians are less familiar with it and less likely to recognise it so the contact tracing is likely to be arduous. Young people between the ages of 18 and 24 are at risk for being incompletely vaccinated.

Treatment is the same as in children.

Subacute sclerosing panencephalitis is a side effect occurring in about 0.01% of cases, and present a few years after measles infection.

Making every contact count

As well as watching out for measles and managing possible cases appropriately (both clinically and through infection control), we also have a duty to consider discussing vaccination with vaccine-hesitant parents or patients. This is easier said than done and takes some courage and diplomacy, but is an important part of our role. This blog and video is a few years old now, but still really useful. It’s never too late to get vaccinated against measles.


  1. Notifiable diseases: form for registered medical practitioners. UK Health Security Agency. GOV.UK. Last updated 30 June 2016.
  2. Team DFTB. Vaccine hesitancy: Margie Danchin at DFTB18, Don’t Forget the Bubbles, 2018.

Further reading