Overview

Measles is a contagious viral disease that spreads through airborne transmission, when an infected person breathes, coughs, or sneezes. Measles can affect anyone but is most common in children and individuals who have not been vaccinated. The virus primarily infects the respiratory tract but can spread through the body.

Symptoms of measles include a rash, high temperature, cough, and runny nose. Measles infection also damages and suppresses the whole immune system, so individuals who have had it are more susceptible to other infectious diseases.¹ This immunosuppression can persist for up to three years. Although it is generally not a serious illness, measles can be associated with more life-threatening complications.

Vaccination remains the most effective way to prevent measles. In this article, we will look at the symptoms and transmission of measles and its long-term effects on health.

What is measles?

Measles is caused by the rubeola virus, which belongs to the morbillivirus family (MeV). It is an airborne disease that can spread through the air when an infected person sneezes, coughs, or talks. The airborne droplets carrying the virus can linger in a room for up to two hours after the infected person has left. Droplets can also land on surfaces and spread the virus. 

Measles spreads by direct contact with an infected person. If an unvaccinated person inhales these airborne particles, they are at high risk of measles infection. 

Historical context

The World Health Organisation (WHO) reported that major measles epidemics occurred approximately every two to three years, and caused an estimated 2.6 million deaths, before the introduction of the measles vaccine. Accelerated immunisation programmes are believed to have successfully prevented an estimated 57 million deaths between 2000–2022. 

Incidence of measles

The Vaccine Knowledge Project in Oxford estimates that measles still causes death in about 1 in 5000 cases in high-income regions of the world, but up to 1 in 100 in poorer regions. Before widespread vaccination, the disease caused an estimated 2.6 million global deaths each year and remains a major cause of death worldwide. WHO reported that measles cases rose by 18% and deaths by 43% in 2022 compared with 2021. During this time, worldwide vaccination coverage also declined to its lowest level since 2008.

In countries like the UK, measles causes death in about 1 in 5000 cases. Despite the availability of a safe and effective vaccine, around 350,000 measles cases were reported worldwide in 2018 which resulted in an estimated 142,300 deaths. In 2017, measles cases spiked worldwide, causing the death of 110,000 people, mostly children under the age of 5 years and immunocompromised adults.² 

Transmission of measles

Measles is highly contagious. If one person has measles, up to 10 or 12 people in close contact with them are likely to become infected if they are not vaccinated.³ Transmission of measles occurs through respiratory droplets expelled from the body by coughing, sneezing, and talking. Measles can be caught by being in close contact, shaking hands, kissing, hugging, and sharing food. Additionally, infected pregnant women can pass the virus to their babies.

An example of how infectious measles can be was highlighted in a news item on the BBC news website warning patients who had visited an A&E department in a hospital in Durham on a specific date to be on alert for measles, as there had been a confirmed case in the department during that time. 

Incubation period of measles

The incubation period refers to the length of time taken for symptoms of a disease to appear after exposure to a pathogen. The incubation period for measles is around 10-14 days after infection but can be as short as seven days or as long as 21 days.⁴

Infectious period for measles

The infectious period is the time during which an individual with an illness can spread the infection to others. It is thought that the infectious period for measles is around four days before the rash appears, and for a further four days after the rash has developed. Therefore the total infectious period is around eight days. 

Diagnosis and treatment

A general practitioner (GP) can usually diagnose measles based on a thorough medical history and observable factors such as rash and the presence of other symptoms. Some laboratory tests can confirm the diagnosis. A swab can be used to collect saliva samples or a blood sample can be taken to measure for a measles-specific immunoglobulin M (IgM). 

Symptoms of measles

Symptoms of measles usually occur around 8-12 days after exposure to the virus. The main symptoms include: 

• High temperature (pyrexia)
• Tiredness
• Cough
•  Bloodshot eyes (conjunctivitis)
• Runny nose
• Sore throat
• White spots in your mouth (Koplik spots)
• Muscle pain
• Light sensitivity

Measles rash

Measles is associated with a red rash that usually begins on the face and then spreads across the whole body. White spots may then appear over the red rash. This rash can last around 7-10 days. 

Complications of measles

Measles can lead to more severe complications, which may include:

• Otitis media (ear infection)
• Diarrhea
• Pneumonia
• Encephalitis
• Immune amnesia
• Acute disseminated encephalomyelitis (ADEM)
• Death

Long-term effects of measles on health

Immune amnesia 

An acute measles infection causes immunosuppression through a process called immune amnesia. This results in a strong immunity to the measles virus itself but an increased susceptibility to all other infections.

Subacute sclerosing panencephalitis 

In rare cases, measles can lead to a condition called subacute sclerosing panencephalitis (SSPE). This is a very serious infection which causes damage to the central nervous system. Symptoms can develop years after the initial infection. These symptoms include dementia, loss of motor control, epilepsy and eventually death. Children infected at a young age may develop subacute sclerosing panencephalitis many years later.

Immunocompromised patients may experience a reduced clearance of the measles virus, which can lead to progressive lung or nervous system damage. In rare cases, they can also acquire measles from the vaccine itself. For this reason, measles vaccination (and vaccination with other live vaccines) is generally not recommended for immunocompromised individuals. 

Treatment approaches 

There is no specific medical treatment for measles as it is a viral illness, so it typically needs to run its course. Symptoms can be managed to keep the individual comfortable, such as giving over-the-counter pain relief and ensuring adequate hydration alongside isolation. More serious complications require medical intervention. 

The most effective approach to combat measles is eradication by vaccination. Anyone who has not received the measles vaccine is at risk of contracting the disease. Before the vaccine programme was introduced, almost everyone contracted measles as a child. However, if you have had measles or had the vaccine, you are likely immune. 

Measles vaccine

A live vaccine became available in America in 1963 and in the UK in 1968. The UK Health Security Agency estimates that 20 million measles cases and 4,500 deaths have been averted since the introduction of the measles vaccine. Although measles transmission was briefly stopped in the UK altogether in 2016 and 2017, it re-started in 2018.

It stopped again during the COVID-19 pandemic. Measles cases increased again during 2023 and have continued to grow. According to the Vaccine Knowledge Project, the UK Health Security Agency declared a national incident at the start of 2024 and encouraged parents to get their children vaccinated against measles, if they had not already. 

Efficacy of the measles vaccine 

The measles vaccine is part of the vaccination we know as MMR which protects against measles, mumps, and rubella. It is a live vaccine and has proved to be one of the most cost-effective interventions in global health.⁵ In the UK, babies receive the vaccine at around one year old and a second dose is administered between 3 and 5 years of age. 

Despite a safe and effective measles vaccine, measles still kills around 800,000 people annually. These are mostly children in developing countries.⁶

Herd immunity and vaccination coverage

Herd immunity occurs when a significant portion of a population becomes immune to an infectious disease, limiting further disease spread. Diseases spread when some of a population is susceptible to the disease, but herd immunity reduces the risk of spread by decreasing the likelihood of transmission; those who are not immune are indirectly protected because ongoing disease spread is very small. People who cannot be vaccinated due to compromised immunity or babies under the age of 12 months depend on this herd immunity for protection.

The proportion of a population needed to achieve herd immunity varies by disease. For example, a very contagious disease like measles needs more than 95% of the population to be immune to achieve herd immunity.⁷

Challenges in achieving global vaccination targets

Global vaccination rates are still not optimal and recent drops in uptake have resulted in some outbreaks of measles. Herd immunity weakens when the vaccination rate drops. In the late 1990s, a paper claiming links between MMR and autism unfortunately led to some parents refusing to vaccinate their children. Despite the author being discredited and the journal withdrawn, it negatively impacted vaccination rates and perception of the vaccine. 

A challenge is the influence of famous people or politicians declaring themselves not in favour of vaccines, allowing the spread of the anti-vaccine movement.⁸ In addition, the presence of numerous anti-vaccination websites and social media threads contribute to the increase of anti-vaccine support. These perceptions and actions need to be addressed to maintain optimal vaccine uptake and herd immunity. 

Summary

Measles is a highly contagious viral illness that spreads easily among vulnerable and unvaccinated populations by close contact with an infected person. Whilst it is usually a fairly mild illness that can resolve on its own, it can sometimes lead to very serious complications and death.

Measles vaccination programmes since the 1960s have made this disease rare in developed countries due to herd immunity. However, a recent decline in vaccination rates has led to a rise in cases of the illness and increased the potential for long-term health problems due to complications.