Measles, mumps, and rubella
Introduction
Measles, mumps, and rubella (MMR) are three highly contagious viral diseases that have significant public health implications. These diseases are preventable through vaccination, specifically the MMR vaccine, which is a combined vaccine that protects against all three infections. This article provides a comprehensive and detailed exploration of each disease, their epidemiology, clinical manifestations, complications, and prevention strategies.
Measles
Virology
Measles is caused by the measles virus, a single-stranded, negative-sense RNA virus belonging to the genus Morbillivirus within the family Paramyxoviridae. The virus has a lipid envelope derived from the host cell membrane and surface glycoproteins that facilitate host cell entry.
Epidemiology
Before the introduction of the measles vaccine, measles was a ubiquitous childhood infection. Despite high vaccination coverage in many countries, measles outbreaks still occur, primarily due to vaccine hesitancy and gaps in immunization coverage. Measles remains endemic in several regions, particularly in parts of Africa and Asia.
Clinical Manifestations
The incubation period for measles is typically 10-14 days. The disease progresses through several stages:
- **Prodromal Phase**: Characterized by high fever, cough, coryza, and conjunctivitis. Koplik's spots, small white lesions on the buccal mucosa, are pathognomonic for measles.
- **Exanthem Phase**: A maculopapular rash begins on the face and spreads cephalocaudally. The rash usually lasts for about 5-6 days.
Complications
Complications of measles can be severe and include pneumonia, encephalitis, and subacute sclerosing panencephalitis (SSPE). Immunocompromised individuals and malnourished children are at higher risk for severe disease.
Prevention
The primary method of prevention is the MMR vaccine, which is typically administered in two doses. High vaccination coverage is essential to achieve herd immunity and prevent outbreaks.
Mumps
Virology
Mumps is caused by the mumps virus, a single-stranded, negative-sense RNA virus belonging to the genus Rubulavirus within the family Paramyxoviridae. The virus has a lipid envelope with hemagglutinin-neuraminidase and fusion glycoproteins.
Epidemiology
Mumps was a common childhood disease before the introduction of the mumps vaccine. Despite widespread vaccination, mumps outbreaks still occur, particularly in close-contact settings such as schools and colleges.
Clinical Manifestations
The incubation period for mumps is about 16-18 days. Clinical features include:
- **Parotitis**: Swelling and tenderness of the parotid glands, often bilateral.
- **Non-specific symptoms**: Fever, headache, myalgia, and malaise.
Complications
Complications of mumps can include orchitis, oophoritis, meningitis, and pancreatitis. Orchitis can lead to infertility in post-pubertal males.
Prevention
The MMR vaccine is the primary preventive measure against mumps. Two doses of the vaccine are recommended for optimal protection.
Rubella
Virology
Rubella, also known as German measles, is caused by the rubella virus, a single-stranded, positive-sense RNA virus belonging to the genus Rubivirus within the family Matonaviridae. The virus has a lipid envelope with glycoprotein spikes.
Epidemiology
Rubella is generally a mild disease but poses significant risks during pregnancy, leading to congenital rubella syndrome (CRS). Widespread vaccination has significantly reduced the incidence of rubella and CRS in many countries.
Clinical Manifestations
The incubation period for rubella is typically 14-21 days. Clinical features include:
- **Rash**: A fine, pink maculopapular rash that begins on the face and spreads to the trunk and extremities.
- **Lymphadenopathy**: Enlargement of posterior auricular and suboccipital lymph nodes.
- **Non-specific symptoms**: Mild fever, headache, and arthralgia.
Complications
The most serious complication of rubella is CRS, which can result in severe birth defects such as deafness, cataracts, heart defects, and developmental delays.
Prevention
The MMR vaccine is highly effective in preventing rubella. Two doses are recommended for complete immunization.