Measles symptoms, complications and how it spreads

What is measles?

Measles is a highly contagious viral illness that spreads through tiny droplets from coughing or sneezing. 

It can stay in the air or on surfaces for up to two hours, making it easy to catch in homes, schools, or public places. 

Measles is more contagious than flu or COVID-19. Its R₀ (basic reproduction number) is 12–18, meaning one infected person can spread it to up to 18 others in an unvaccinated population. 

Even in countries like the UK - where measles was once eliminated - small drops in vaccination rates can lead to outbreaks. 

How measles spreads 

The virus is spread through: 

• Airborne droplets from coughing or sneezing 

• Contaminated surfaces that remain infectious for up to two hours 

• Close contact in households, schools, and public spaces 

Outbreaks often start when someone infected abroad enters a community with low MMR vaccine uptake. 

Symptoms and course of illness 

After exposure, symptoms usually appear after 10–12 days (range 7–21 days). 

Early signs: 

• High fever, tiredness, loss of appetite 

• Cough, runny nose, red or watery eyes 

• Tiny white spots inside the mouth (Koplik spots) 

Rash: 

• Red-brown, blotchy rash starting on the face and spreading down the body 

• Infectious from four days before the rash until four days after 

Complications 

While most people recover within 7-10 days, measles can cause serious or fatal complications, especially in: 

• Young children 

• Pregnant women 

• People with weakened immune systems 

Possible complications include: 

• Ear infections and hearing loss 

• Pneumonia (main cause of measles-related deaths) 

• Encephalitis (brain inflammation) 

• Seizures 

• Diarrhoea and dehydration 

• Pregnancy risks such as miscarriage or premature birth 

• In rare cases, death 

In the UK, measles outbreaks also strain NHS resources - leading to A&E visits, staff absences, and temporary ward closures.