9.18. Measles

Guidelines for Managing Measles

This guidance is intended to assist healthcare workers in the management of patients, staff and visitors who present with symptoms suggestive of measles. It is critical to implement these guidelines to prevent and control the spread of infectious diseases in an effort to avert any outbreaks.

Disease Description

Measles is caused by a single-stranded, enveloped RNA virus with 1 serotype, which allows for vaccine effectiveness against all genotypes. The viral genome has 8 clades (A–H) with 24 genotypes, enabling epidemiologic surveillance to determine the geographic origin of a particular genotype.

Humans are the only natural hosts of the measles virus.

Transmission

• Measles is a highly contagious disease — up to 18 susceptible persons with close contact to a measles case will develop measles (basic reproduction number R₀ = 12–18).
• Measles virus is transmitted primarily by respiratory droplets or airborne spray to mucous membranes of the upper respiratory tract or conjunctiva when an infected individual coughs or sneezes.
• The virus can remain infectious in the air for up to two hours within a radius of 2–4 metres after an infected person leaves an area.

Incubation Period

• Approximately 10–12 days from exposure to onset of fever and non-specific symptoms.
• Approximately 14 days (range 7–18 days; rarely up to 19–21 days) from exposure to onset of rash.

Period of Communicability

• Measles can be transmitted from 4 days before rash onset (1–2 days before fever onset) to 4 days after rash onset.
• Due to the high transmission efficiency of measles, outbreaks have been reported in populations where only 3–7% of individuals were susceptible.

Immunity

• Infants are generally protected until 5–9 months of age by passively acquired maternal measles antibodies.
• Natural infection confers lifelong immunity.
• Vaccination with measles-containing vaccine has been shown to be protective for at least 20 years and is considered to confer long-term, likely lifelong, immunity following two doses.

Clinical Features

Prodrome and General Symptoms

• A 2–4 day prodrome of fever, malaise, cough, runny nose (coryza), and conjunctivitis — the "3 Cs" (cough, coryza, conjunctivitis).
• During the prodrome, the patient is shedding virus and is highly contagious.
• A harsh, non-productive cough is present throughout the febrile period, persists for 1–2 weeks in uncomplicated cases, and is often the last symptom to disappear.
• Generalized lymphadenopathy is common in young children; photophobia and arthralgia are more common in older children.

Koplik Spots

• Appear 1–2 days before rash onset and persist for 2–3 days after rash disappearance.
• Slightly raised white dots (2–3 mm diameter) on an erythematous base on the buccal mucosa — a pathognomonic finding for measles. May number 5 to several hundred.

Rash

• A large, blotchy red rash begins behind the ears and on the face within 2–4 days of prodromal symptoms, at which time high fever also develops.
• The rash spreads cephalocaudally (head downwards to the trunk and extremities), peaks in 2–3 days, and fades in the same pattern as it appeared, often followed by fine desquamation.

Complications

• Respiratory: pneumonia (most common cause of death from measles), laryngotracheobronchitis (measles croup), bronchiolitis, otitis media, mastoiditis.
• Gastrointestinal: diarrhoea, dehydration, malabsorption and malnutrition (contributing to high mortality in developing countries).
• Ocular: keratitis, ulcerating keratomalacia (particularly in vitamin A-deficient children, can cause blindness).
• Skin: cancrum oris (noma), pyoderma.
• Adenitis: cervical, mesenteric.
• Cardiac: myocarditis, pericarditis.

High-risk groups for severe illness and complications include: infants and children < 5 years, adults > 20 years, pregnant women, and immunocompromised individuals (including those with leukemia and HIV infection).

Diagnosis

• Laboratory testing is necessary for definitive diagnosis as multiple conditions can mimic measles, including rubella, erythema infectiosum (Fifth disease), roseola infantum, dengue, Zika, chikungunya, and scarlet fever.

Specimen Collection Guide:

Differential Diagnosis

Comparison of measles to arboviral and exanthematous diseases:

Case Fatality

• In industrialized countries, the case-fatality rate for measles is approximately 1 per 1,000 reported cases.
• In developing countries, the case-fatality rate is estimated at 3–6%; the highest rate occurs in infants 6–11 months of age, with malnourished infants at greatest risk.
• Young age, crowding, underlying immunodeficiency, vitamin A deficiency, and lack of access to medical care are factors leading to high case-fatality rates in developing countries.

Treatment and Management

There is currently no specific antiviral treatment for measles. Management is supportive:

• Relieve common symptoms: fever, cough, nasal congestion, conjunctivitis, sore mouth.
• Nutritional support to reduce the risk of malnutrition due to diarrhoea, vomiting, and poor appetite.
• Encourage breastfeeding where appropriate.
• Use oral rehydration salts as needed to prevent dehydration.
• Administer vitamin A to all acute measles cases:
  • < 6 months of age: 50,000 IU orally — give immediately on diagnosis and repeat the next day
  • 6–11 months of age: 100,000 IU orally — give immediately on diagnosis and repeat the next day
  • ≥ 12 months of age: 200,000 IU orally — give immediately on diagnosis and repeat the next day
  • If clinical signs of vitamin A deficiency (e.g., Bitot's spots): give a third dose 4–6 weeks later

Isolation

• Isolate sick individuals from 4 days before to 4 days after the onset of the rash. In immunocompromised hosts: for the duration of the illness.
• All uncomplicated suspected and confirmed cases of measles will be isolated at home. Masks should be worn if there is any possibility of contact with others in the home.

Ending Isolation

• Suspected case: isolation can be ended upon receipt of a negative PCR result or negative serology.
• Confirmed case: isolation ends on Day 5 after rash onset (4 days after rash onset), when the individual is no longer considered infectious.
• Confirmed cases with immunocompromised status: isolate for the duration of the illness.

Care of Exposed Individuals

Definitions

Exposed individuals / contacts: anyone sharing the same air space — usually an enclosed area (same household, room, school, health facility waiting room, office, or transport) — for any length of time with a case during the infectious period. Because measles virus remains contagious in air or on surfaces for up to two hours, transmission can occur even if the contact was not in the same room at the exact same time as the case.

Non-immune persons: those who are unvaccinated, without proof of vaccination, or without proof of past infection.

Quarantine

• Contacts will not be quarantined but will be advised to self-monitor for signs and symptoms of measles for 21 days from first contact with the confirmed case.
• During this period, contacts will be placed on airborne precautions.
• Contacts unable to provide evidence of vaccination status will be managed as unvaccinated contacts.

Case Definitions

Suspected Case

Any person with fever and maculopapular (non-vesicular) rash AND cough, coryza (runny nose), or conjunctivitis (red eyes).

Upon investigation, all suspected cases should be classified into one of the following mutually exclusive categories:

1. Laboratory-confirmed case: a suspected case with laboratory confirmation of measles (IgM or PCR positive) and/or epidemiological linkage to a laboratory-confirmed case.
2. Clinically confirmed case: a suspected case that has not been adequately investigated.
3. Discarded case: a suspected case that, upon adequate investigation including a blood specimen collected in the appropriate time frame, lacks serologic evidence of measles/rubella infection.
4. Imported case: a confirmed case with epidemiological and/or virologic evidence of exposure outside the Western Hemisphere during the 7–21 days prior to rash onset. Local exposure must be excluded after careful community investigation.
5. Import-related case: a confirmed case with epidemiological and/or virologic evidence of exposure locally as part of a transmission chain initiated by an imported case. A chain of transmission is two or more confirmed cases that are epidemiologically linked.

Identification, Notification, and Investigation

Identification

A patient in whom a healthcare provider suspects measles, or any patient with fever and rash, is - for surveillance purposes - considered a suspected measles case.

Notification

Investigation

• Upon notification, all suspected cases will be investigated immediately.
• Regional investigation teams will be in charge of the investigation.
• Investigations will comprise: a home visit within 48 hours of notification; collection of complete relevant data (date of rash onset, date of notification, date of investigation, date sample taken, type of rash, presence of fever, dates of previous measles/rubella vaccinations); and active measles case-searches (contact investigations).

Key Messages for Healthcare Workers

• Suspect measles in any patient with fever, maculopapular rash, and the 3 Cs (cough, coryza, conjunctivitis) — especially in unvaccinated individuals or those with recent travel history.
• Notify the Epidemiology Unit within 24 hours of any suspected case — do not wait for laboratory confirmation.
• Collect specimens (blood for IgM and nasopharyngeal swab for RT-PCR) at first contact — do not delay for the ideal window.
• Administer vitamin A to all acute measles cases regardless of prior dosing history.
• Post-exposure MMR vaccination within 72 hours can prevent disease in exposed non-immune contacts.
• Place all suspected measles cases on airborne precautions immediately.

Reference List

• World Health Organization (2023). Vaccine Preventable Diseases Surveillance Standards — Measles. Available from: https://cdn.who.int/media/docs/default-source/immunization/vpd_surveillance/vpd-surveillance-standards-publication/who-surveillancevaccinepreventable-02-measles-r2.pdf
• Pan American Health Organization / World Health Organization (2023). Guidelines for the Surveillance of Measles, Rubella, and Congenital Rubella Syndrome in the Region of the Americas.
• Centers for Disease Control and Prevention (2024). Measles (Rubeola): For Healthcare Professionals. Available from: https://www.cdc.gov/measles/hcp/index.html
• World Health Organization (2023). Measles vaccines: WHO position paper — April 2017 (reaffirmed 2023). Weekly Epidemiological Record.