Introduction

Measles is caused by a virus that can lead to serious disease targeting the respiratory system. This disease is highly contagious, with symptoms commonly presenting as flu-like and the development of a red rash. Measles tends to be more common in children, spreading from person to person through airborne transmission such as sneezing, coughing, or breathing.¹ Although the MMR (Measles, Mumps, and Rubella) vaccine can prevent measles, it remains prevalent across the globe. In 2022, there were 205,101 reported cases of measles worldwide and an estimated 136,000 deaths from the disease. This highlights measles can become extremely serious when transmitted. Especially if an individual develops a co-infection that weakens the immune system, leading to potentially fatal health outcomes. This article will explore measles in more depth, including co-infections with other viruses, the impact of the COVID-19 pandemic on measles immunisation, misconceptions about vaccine usage, and future prospects for disease control.

What is measles?

The viral disease measles is a vaccine-preventable infectious disease, yet it remains highly contagious and globally prevalent. It initially infects the respiratory system and then spreads to the rest of the body, potentially causing death. Countries around the world have attempted to eliminate the virus, with the World Health Organization (WHO) aiming to achieve this by 2030. Mass vaccination rollout programmes have prevented around 57 million measles-related deaths from 2000 to 2022. Although deaths still occur from measles,⁶ this represents a significant decrease in the mortality rate.

Symptoms and complications

Typically characterised by the presence of a red rash, measles symptoms can be divided into three basic categories. Flu-like symptoms tend to develop first, followed by skin and oral signs and symptoms a few days after. It is important to note that if these signs and symptoms appear, seek medical advice and contact your GP if you are not sure you have both doses of the MMR vaccination.

• Flu-like symptoms: High fever, coughing and sneezing, a blocked or runny nose and irritation of the eyes (conjunctivitis).
• Skin symptoms: a red blotchy rash which usually begins to develop on the head/face and then spreads down the lower portion of the infected individual's body.
• Oral symptoms: white flecks/spots displayed on the inner cheek and inner lip of the infected individual.

Further complications can occur following these symptoms, ranging from milder issues such as painful ear infections and diarrhoea to more serious complications like blindness, pneumonia, encephalitis (inflammation of the brain), and even death. Severe complications are more likely to occur in individuals who are not vaccinated against measles or who have weakened immune systems, such as the elderly, children, and those with underlying health conditions.

Transmission and prevention

Measles spreads very easily from person to person via respiratory droplets expelled into the air when an infected individual talks, breathes, coughs, or sneezes. It can affect people of any age but is more common in children. Before the development of the MMR vaccine, measles epidemics were widespread, resulting in around 2.6 million deaths annually. In 1963, the MMR vaccine was developed providing immunity to individuals unexposed to the virus. The first dose is administered to children under 12, often in the early years of life, because it tends to target this age group. Unfortunately, not all children are immunised due to various factors, including limited access to healthcare, anti-vaccination beliefs, or a lack of education about the importance of the disease and how to prevent it.

Measles and the immune system

The immune system helps our body recognise and fight off pathogens (bacteria, viruses, parasites, or fungi). When measles enters the body, it causes immunosuppression, a condition where the immune system's ability to fight disease is reduced. This occurs because the disease affects the activation of the immune system, hindering its response to infection. Consequently, the immune system's success rate in managing and clearing infections decreases, allowing the disease to spread and cause damage to the body. Measles-induced immunosuppression can last from a few weeks to months after the appearance of the typical red rash. It decreases the immune system's ability to identify foreign pathogens.² Additionally, the measles virus impairs the immune system's ability to recognise previously encountered pathogens by destroying immune memory cells, called immune amnesia.³ Ineffective pathogen recognition from the immune system increases an individual's susceptibility to secondary infections.⁴ Therefore, co-infection with another virus or bacteria is a large cause of death from measles.⁵

Common co-infections with measles

Co-infection means more than one pathogen has infected and invaded an individual's immune system at the same time. As previously mentioned, immunosuppression induced by measles-virus increases the likelihood of co-infection. There are numerous secondary viral infections associated with measles that can result in co-infections damaging different parts of the body, these include:

• Respiratory secondary infections: Influenza virus, Respiratory Syncytial Virus (RSV) and, more recently, SARS-CoV-2⁴
• Gastrointestinal secondary infections: Rotavirus, norovirus and cytomegalovirus⁶
• Other viral secondary infections: Human Immunodeficiency Virus (HIV) and Herpes Simplex Virus (HSV)⁵

Measles disrupts the immune system, resulting in a weakened response and the destruction of vital immune memory cells, which increases susceptibility to secondary infections by other types of viruses. This, in turn, leads to further health complications that tend to be more severe and have a higher risk of resulting in fatal outcomes.⁵

Preventing measles and associated viral infections

Immunisation decreases an individual's susceptibility to disease by providing immunity (protection) against particular diseases. The more people immune to a particular virus, the less likely it can spread and cause disease. This allows us to establish herd or population immunity.⁷  

The introduction of the MMR vaccine made measles a highly vaccine-preventable infectious disease. The vaccine works by providing the body with immunity against four diseases: measles, mumps, rubella and chickenpox. It is recommended that children aged 12 months to 12 years receive two doses of the vaccine to allow for increased immunity against the measles virus(. Many countries have adopted immunisation strategies to ensure vaccination against measles. In the United Kingdom, both doses of the MMR vaccine are offered to all children for free. The World Health Organisation states that, in 2022, 83% of babies globally had received at least one dose of the MMR vaccine before they turned one year old. In previous years, the percentage was higher but due to the global COVID-19 pandemic, there have been disruptions and delays in vaccination rollouts.⁸

Vaccination is the best preventative measure for measles. However, it is still important that general preventative measures are followed, as not everyone is vaccinated and herd immunity cannot necessarily be established amongst all communities.⁷ General preventative strategies include hygiene practices such as washing hands, use of disinfectants and correct use/disposal of tissues when coughing and sneezing. Due to the measles virus being so contagious, t if an individual, such as a school child or a worker, becomes infected with the measles, the school/workplace must be notified. In consequence, quarantine measures can be followed to avoid exposure to measles during an outbreak.

Misconceptions and public health challenges

A large misconception surrounding measles is related to the usage of the MMR vaccine. People are worried because of a link between the vaccine and autism spectrum disorder (ASD). These concerns were derived in the 1990s due to publications that claimed the MMR vaccine correlated with the risk of developing ASD Publications covering this topic were reviewed and deemed inaccurate, as there was no direct evidence between immunisation with the MMR vaccine and ASD. The vaccine aims to prevent the measles virus and has not been proven to have any relation to the brain or development of neurological disorders. 

Misinformation leads to vaccine hesitancy, making it crucial for public efforts to address measles and other viral infections. Global cooperation and efforts include vaccination campaigns and education and awareness programs aim to eliminate the disease. Examples of such campaigns include the ‘Immunization Agenda 2030 Measles & Rubella Partnership,’ which collaborates with major public health organisations such as the Red Cross, UNICEF, and the United Nations. This partnership follows seven-step criteria to provide funding and healthcare measures to help countries manage and prevent measles outbreaks and minimise poor health outcomes. This is particularly important now more than ever, as although 83% vaccination coverage of children before their first birthday is high, it is the lowest value it has ever been.

Summary

Without vaccination, measles can be a life-threatening and deadly disease. The previously high mortality rates, especially among children, have significantly decreased since the introduction of the MMR vaccine. However, vaccine hesitancy and disruptions in vaccination rollout due to the COVID-19 pandemic have reduced vaccination coverage, leading to continued measles epidemics. It is crucial to increase awareness about measles, understand its signs and symptoms, and prevent transmission. The future of its eradication depends on global efforts to combat measles collectively. 

Measles is not the only virus of concern. The recent experience of living through a global pandemic highlights the importance of general hygiene practices in preventing infections, including those that could lead to co-infections, resulting in more severe and potentially fatal outcomes. Achieving higher vaccine coverage and herd immunity may pave the way to the elimination and, hopefully, eradication of measles.