Measles (Rubeola)
Definition
Measles is a highly contagious, acute febrile illness caused by the measles virus, a single-stranded RNA virus from the Paramyxoviridae family. It is classically characterized by a distinct prodromal phase of high fever and the "three Cs" (cough, coryza, conjunctivitis), followed by a pathognomonic enanthem (Koplik's spots) and a distinctive, cephalocaudal maculopapular exanthem (1, 2).
Epidemiology
In Malaysia, measles remains a significant and persistent public health concern despite a long-standing national immunisation programme, first introduced in 1982 and updated to a two-dose MMR schedule in 2004 (3). While the country officially aims for elimination status, the goal is continuously challenged by recurrent outbreaks. These outbreaks are often concentrated in specific communities with low vaccination coverage, which may be influenced by factors such as vaccine hesitancy, logistical barriers in remote areas, and the presence of under-immunised migrant populations (3). A revealing study in Pahang underscored the key local risk factors for confirmed measles, which included an indigenous background, a history of direct contact with a known case, and, most critically, an incomplete immunisation status (4). Achieving and maintaining the herd immunity threshold, which requires at least 95% two-dose vaccination coverage, is essential to protect the entire population, including those who cannot be vaccinated. However, current challenges make this a difficult target to sustain consistently (3). [Specific prevalence data from the latest National Health and Morbidity Survey was not available, highlighting a critical gap in current national-level surveillance data that is needed for targeted public health interventions].
Globally, measles is experiencing a dramatic and alarming resurgence, serving as a "canary in the coal mine" for the strength of public health systems worldwide. The World Health Organization (WHO) reported an estimated 107,500 measles deaths in 2023, with the overwhelming majority occurring in unvaccinated or under-vaccinated children under the age of five (5). This global regression, driven by severe disruptions to routine immunisation during the COVID-19 pandemic, falling public trust, and the proliferation of misinformation, significantly increases the risk of viral importation into Malaysia. This makes robust clinical vigilance and a high index of suspicion more critical than ever for frontline clinicians (5, 6).
Pathophysiology
The measles virus is transmitted with extreme efficiency via respiratory droplets and airborne aerosols, with an R-naught (R₀) of 12-18, making it one of the most contagious human diseases known (4, 7). The pathogenesis is a masterful cascade of immunological subversion. The virus's journey begins not on the respiratory epithelium, but within the immune cells—alveolar macrophages and dendritic cells—residing in the respiratory tract. Viral entry is mediated by its hemagglutinin (H) protein binding to the SLAM/CD150 receptor, a protein expressed almost exclusively on immune cells like T-lymphocytes, B-lymphocytes, and macrophages (7).
This initial infection is followed by replication in regional lymph nodes and a primary viremia, which disseminates the virus throughout the entire reticuloendothelial system. A massive, high-titre secondary viremia then occurs, during which infected lymphocytes act as "Trojan horses." They migrate into tissues and transmit the virus to the epithelial cells of the skin, respiratory tract, conjunctiva, and gastrointestinal tract. This late-stage infection of epithelial surfaces is what produces the characteristic clinical signs and facilitates viral shedding, allowing transmission to new, susceptible hosts (7, 8).
The most insidious aspect of measles pathogenesis is the profound and prolonged immunosuppression it induces, a phenomenon aptly termed "immune amnesia." The virus's specific targeting and infection of SLAM-expressing memory T- and B-lymphocytes leads to their widespread destruction. This process effectively erases the body's immunological memory of past infections and vaccinations, leaving the patient highly vulnerable to a host of secondary opportunistic infections. This state of heightened susceptibility can last for many months, with some studies suggesting an increased risk of mortality from other childhood diseases for up to three years after the acute measles infection has resolved. This makes it clear that the benefit of the MMR vaccine is not merely the prevention of measles; it is the preservation of a child's entire, hard-won repertoire of acquired immunity (8).
Clinical Presentation
The clinical course of measles is remarkably predictable. After an average incubation period of 10-14 days, the illness begins its characteristic progression (2).
Diagnostic Clues: The single most important diagnostic sign is Koplik's spots. These pathognomonic lesions are small, 1-2mm bluish-white spots on an erythematous base, found on the buccal mucosa, typically opposite the second molars. They are often described as looking like "grains of salt on a red background." They appear 1-2 days before the rash and fade quickly, so a careful oral examination early in the illness is crucial. The classic clinical triad that defines the prodrome is a hacking cough, profuse coryza, and non-purulent conjunctivitis.
Common Symptoms:
High fever (often reaching >40°C), which typically rises in a stepwise fashion during the prodrome and spikes with the onset of the rash.
Intense malaise, irritability, and prostration, often appearing more severe than expected for a typical viral illness.
A harsh, non-productive, and persistent cough.
Profuse, clear coryza (runny nose).
Bilateral conjunctivitis (red, watery eyes), often associated with significant photophobia.
A generalized, erythematous, maculopapular rash that is initially blanching. It classically begins on the face, along the hairline and behind the ears. Over 2-3 days, it spreads in a distinct cephalocaudal (head-to-toe) and centrifugal (center-to-periphery) pattern. The lesions often become confluent, especially on the face and upper trunk, creating a blotchy, erythematous appearance. The rash begins to fade after 3-4 days in the same order it appeared, often leaving a brownish, coppery discoloration and fine, brawny desquamation (skin peeling).
⚠️ Red Flag Signs & Symptoms:
Respiratory distress (tachypnoea, nasal flaring, intercostal retractions, grunting) suggesting the onset of pneumonia, the most common fatal complication.
Altered mental status (drowsiness, confusion, lethargy), seizures, or any new focal neurological deficits which are ominous signs pointing towards acute encephalitis.
Persistent vomiting, inability to retain oral fluids, and clinical signs of dehydration (e.g., sunken eyes, dry mucous membranes, reduced skin turgor, decreased urine output) which necessitate urgent fluid resuscitation.
A hemorrhagic rash (petechiae or purpura), known as "black measles," which indicates severe disease with a higher mortality rate.
Complications
Complications are distressingly common, occurring in up to 30% of reported cases, and are the primary driver of measles-associated morbidity and mortality. Hospitalisation is required in about 1 in 5 cases (6).
Respiratory: Pneumonia is the most common cause of death in young children, affecting up to 1 in 20 cases. It can be a primary viral pneumonitis (Hecht's giant cell pneumonia) or, more frequently, a secondary bacterial superinfection caused by organisms like Streptococcus pneumoniae or Haemophilus influenzae (6). Laryngotracheobronchitis (croup) is also a frequent complication that can cause significant airway obstruction.
Neurological: The measles virus is neurotropic and can cause devastating neurological damage.
Acute Encephalitis: Occurs in approximately 1 in 1,000 cases, typically presenting with a returning fever, headache, vomiting, and progressing to seizures and altered consciousness about a week after rash onset. The risk of mortality is high (~15%), and permanent neurological sequelae, such as intellectual disability or deafness, occur in 25-40% of survivors (6).
Subacute Sclerosing Panencephalitis (SSPE): This is the most feared long-term complication. It is a rare but invariably fatal progressive degenerative disease of the central nervous system that manifests, on average, 7-10 years after the initial measles infection. It begins insidiously with personality changes and intellectual decline, progressing relentlessly to myoclonic jerks, ataxia, seizures, and ultimately a persistent vegetative state and death. The risk is significantly higher for those infected under the age of two (1, 6).
Gastrointestinal: Diarrhoea is very common (~8% of cases) and, particularly in young children, can lead to life-threatening dehydration and malnutrition (1).
Other: Otitis media is one of the most frequent secondary bacterial superinfections (~7-10% of cases) (1). Less common complications include keratitis (which can lead to corneal scarring and blindness, especially in Vitamin A deficient children), myocarditis, and transient hepatitis.
Prognosis
In uncomplicated cases in well-nourished children, recovery is the norm. However, the prognosis worsens dramatically in the presence of complications. The overall case fatality rate is approximately 1-3 per 1,000 cases in developed countries but can be substantially higher in malnourished and resource-limited populations (6). Factors strongly associated with a poor prognosis include young age (<5 years), severe malnutrition (especially underlying Vitamin A deficiency, which impairs epithelial integrity and immune function), and any form of immunodeficiency (e.g., from leukemia, HIV infection, or immunosuppressive therapy) (1).
Differential Diagnosis
Dengue Fever: This is a critical differential in Malaysia. Both present with high fever, rash, and malaise. However, dengue is distinguished by the absence of the prominent respiratory symptoms (cough, coryza) of measles. The presence of severe myalgia/arthralgia ("break-bone fever"), retro-orbital pain, and warning signs like abdominal pain, persistent vomiting, or mucosal bleeding strongly favour dengue. Laboratory findings of leukopenia with significant thrombocytopenia and a rising hematocrit are classic for dengue (9).
Rubella (German Measles): This is considered due to the similar maculopapular rash. Rubella is typically a much milder illness with a lower-grade fever. The rash is usually more discrete (less confluent), and the presence of prominent post-auricular and sub-occipital lymphadenopathy is a classic distinguishing feature that is less pronounced in measles (2).
Parvovirus B19 (Fifth Disease): This should be considered, especially in school-aged children. It is differentiated by its characteristic biphasic rash: an initial, intensely erythematous "slapped cheek" appearance on the face, followed by a reticular (lace-like) rash on the trunk and limbs. The severe prodromal symptoms of measles are notably absent (2).
Kawasaki Disease: This is an important differential in children under 5. It shares features of high fever (>5 days), rash, and conjunctivitis. However, Kawasaki disease is distinguished by other specific criteria, including changes in the lips and oral cavity (e.g., "strawberry tongue," red, cracked lips), changes in the extremities (erythema/edema of hands and feet), and unilateral cervical lymphadenopathy >1.5cm (2).
Investigations
Immediate & Bedside Tests
Full Blood Count: This is an essential baseline test to assess for lymphopenia and thrombocytopenia, which are common findings (the rationale), helping to support a viral diagnosis and evaluate for potential bleeding risk (the action).
Diagnostic Workup
First-Line Investigations: The initial diagnostic approach for any suspected case requires a dual strategy for maximum sensitivity. A serum sample for measles-specific IgM is crucial, as its presence provides presumptive evidence of a recent infection (the rationale). It's important to note that IgM may be negative if the sample is taken within the first 72 hours of rash onset, so a second sample may be required if clinical suspicion remains high. Simultaneously, a throat or nasopharyngeal swab for measles virus RT-PCR must be collected. It is the most sensitive and specific test in the early phase of illness (the rationale), allowing for definitive confirmation, facilitating viral genotyping for public health surveillance, and enabling rapid public health intervention (the action) (1, 10).
Gold Standard: The combination of a positive measles RT-PCR and/or a positive measles IgM test is considered the gold standard for confirming a case of acute measles (10).
Monitoring & Staging
Chest X-ray: This is not a routine test but is mandatory for any patient with respiratory signs like tachypnoea, increased work of breathing, or crackles on auscultation (the action), as it is vital for diagnosing pneumonia, the most common fatal complication of measles (the rationale) (6).
Lumbar Puncture: This must be performed urgently in any patient with signs of central nervous system involvement like seizures, altered consciousness, or meningism (the action) to obtain cerebrospinal fluid for analysis (cell count, protein, glucose) and measles RT-PCR, which is critical for diagnosing or ruling out encephalitis (the rationale) (6).
Management
Management Principles
The management of measles is primarily supportive, as there is no specific antiviral agent. The focus is on maintaining hydration, ensuring adequate nutritional support, providing symptomatic relief, and, most importantly, the vigilant monitoring for and prompt treatment of complications (2).
Acute Stabilisation (The First Hour)
For a patient presenting with severe disease (e.g., respiratory distress, shock, or altered consciousness):
Airway/Breathing: Assess for and secure a patent airway. Administer high-flow oxygen via a non-rebreather mask to maintain SpO2 >94% (the action), which is critical to prevent tissue hypoxia from complications like severe pneumonia or croup (the rationale). Have a low threshold for escalating to more advanced airway support if there is fatigue or poor air entry.
Circulation: Secure IV access (preferably two large-bore cannulas) and administer a fluid bolus of an isotonic crystalloid like IV Normal Saline or Hartmann's solution at 20mL/kg if signs of dehydration or shock are present (the action), to restore circulatory volume and ensure adequate tissue perfusion (the rationale). Reassess fluid status frequently.
Disability: Rapidly assess neurological status using the Glasgow Coma Scale (GCS) and check a capillary blood glucose to rule out hypoglycemia as a reversible cause of altered mental status.
Definitive Therapy
While there is no cure, two key evidence-based interventions significantly improve outcomes:
Vitamin A Supplementation: The WHO and AAP recommend Vitamin A for all children with measles, especially those with severe disease requiring hospitalisation (11). This is a critical intervention because measles infection rapidly depletes Vitamin A stores, and supplementation has been definitively shown to reduce morbidity and mortality from complications like pneumonia and diarrhoea (the rationale). The oral dose must be given for two consecutive days:
Infants <6 months: 50,000 IU daily
Infants 6-11 months: 100,000 IU daily
Children ≥12 months: 200,000 IU daily (11)
Post-Exposure Prophylaxis (PEP): For susceptible contacts, PEP is a public health emergency measure to prevent further spread.
MMR Vaccine: Administering the MMR vaccine within 72 hours of exposure can prevent or significantly modify the illness in susceptible, immunocompetent individuals aged >6 months (the action), as it rapidly induces an active immune response before the wild virus can establish a full-blown infection (the rationale) (3).
Human Immunoglobulin (IG): For contacts where the live MMR vaccine is contraindicated (infants <6 months, susceptible pregnant women, severely immunocompromised patients) or if it is >72 hours but <6 days post-exposure, IG should be given to provide immediate, temporary passive immunity (3).
Supportive & Symptomatic Care
Fever & Discomfort: Use paracetamol or ibuprofen for fever control and to relieve malaise. Aspirin is absolutely contraindicated in children and adolescents with viral illnesses due to its strong association with Reye's syndrome.
Hydration & Nutrition: Aggressively encourage oral fluids (oral rehydration solution is ideal if there is diarrhoea) and nutrition. If intake is poor or there is persistent vomiting, IV hydration is necessary.
Antibiotics: These have no role in treating the measles virus itself. They are only indicated for the treatment of confirmed or strongly suspected secondary bacterial infections like otitis media or pneumonia.
Key Nursing & Monitoring Instructions
Implement airborne precautions immediately for any suspected case. This requires placing the patient in a negative pressure room if available. All healthcare staff entering the room must wear a fitted N95 respirator, regardless of their own vaccination status or presumptive immunity.
Continuous monitoring of vital signs, especially respiratory rate, work of breathing, and oxygen saturation.
Maintain a strict fluid balance chart, monitoring urine output closely (target >0.5-1mL/kg/hr).
Perform and document regular neurological observations (e.g., GCS, pupil response) for all patients, especially those who are very young or appear toxic, to detect early signs of encephalitis.
Inform medical staff immediately if there is any clinical deterioration, particularly increasing respiratory distress, a drop in oxygen saturation, a fall in GCS, or the onset of seizures.
When to Escalate
A house officer must call their senior (Medical Officer or Specialist) immediately if:
The patient develops any signs of respiratory distress or has an increasing oxygen requirement.
There are any new or evolving neurological signs (seizures, persistent drowsiness, profound irritability, neck stiffness).
The patient is unable to tolerate oral fluids and shows signs of moderate to severe dehydration requiring ongoing fluid resuscitation.
A hemorrhagic rash develops or there are other signs of bleeding.
The patient is known to be severely immunocompromised.
Referral Criteria: Refer to the Paediatric Infectious Disease team for all confirmed or highly suspected cases. Involve the Paediatric Intensive Care Unit (PICU) team early for any patient with severe complications, shock, or impending respiratory failure.
References
Centers for Disease Control and Prevention. (2024). Clinical Overview of Measles. Retrieved from https://www.cdc.gov/measles/hcp/clinical-overview/index.html
Strebel, P. M., & Orenstein, W. A. (2024). Measles. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK448068/
Malaysian Society of Infectious Diseases & Chemotherapy. (n.d.). Measles – Guidelines for Adult Immunisation. Retrieved from https://adultimmunisation.msidc.my/measles/
Jalil, A. A., et al. (2022). Five-Year Trend of Measles and Its Associated Factors in Pahang, Malaysia: A Population-Based Study. International Journal of Environmental Research and Public Health, 19(13), 8017. https://doi.org/10.3390/ijerph19138017
World Health Organization. (2024). Measles. Retrieved from https://www.who.int/news-room/fact-sheets/detail/measles
Mayo Clinic. (2025). Measles - Symptoms & causes. Retrieved from https://www.mayoclinic.org/diseases-conditions/measles/symptoms-causes/syc-20374857
Griffin, D. E. (2016). The Pathogenesis of Measles. In Measles Virus. Springer.
Mina, M. J., Metcalf, C. J. E., de Swart, R. L., Osterhaus, A. D. M. E., & Grenfell, B. T. (2015). Long-term measles-induced immunomodulation increases overall childhood infectious disease mortality. Science, 348(6235), 694–699. https://doi.org/10.1126/science.aaa3662
Ministry of Health Malaysia. (2015). Clinical Practice Guidelines: Management of Dengue Infection in Adults (Third Edition). Putrajaya: MOH.
Centers for Disease Control and Prevention. (2024). Laboratory Testing for Measles. Retrieved from https://www.cdc.gov/measles/lab-tools/rt-pcr.html
World Health Organization. (2017). Vitamin A supplements: a guide to their use in the treatment and prevention of vitamin A deficiency and xerophthalmia. Geneva: WHO.
