Measles, Mumps & Rubella

• Introduction.
• MMR vaccine.
• Measles.
• Mumps.
• Rubella.

Introduction

• Measles, mumps and rubella are three quite different, but potentially serious viral infections that are included together on this page because:
  • Of the need for appropriate Cross Infection control measures in the dental practice.
  • Measles, mumps and rubella are notifiable diseases under the Public Health (Infectious Diseases) Regulations (1988).
    • It is a statutory requirement to inform the local 'Medical Officer for the Environment' (often a consultant in communicable diseases) so that steps can be taken to limit spread of infection and protect vulnerable members of the community.
  • Of their association with the combined MMR vaccine:
    • Current controversies surrounding this vaccine have resulted in children remaining unvaccinated, and these infections may still be encountered in the dental practice.

MMR Vaccine

• The MMR vaccine is a live, attenuated combined vaccine that aims to prevent measles, mumps and rubella.
  • This vaccine remains the focus of considerable controversies and media attention.
  • Single vaccines against either measles, mumps or rubella are no longer available in the United Kingdom, but are available elsewhere in the world.
• Two doses are received before the child enters primary school:
  • The first dose is given at 12-15 months old.
  • The second, booster dose is given at 3-5 years old.
• Measles, mumps and rubella are highly infectious.
  • Accordingly it is essential that as many children as possible receive the MMR vaccine, or outbreaks of these viral illnesses will occur.
• The MMR vaccine is given to all children unless:

• There is a medical contraindication, or
• There is parental refusal - a significant number of parents do withhold consent.

• MMR vaccination is associated with a mild illness (fever, malaise or rash) about a week after the first dose. Parotid swelling occasionally occurs after about three weeks.
  • These side effects are self-limiting and short-lived.
• MMR vaccination has become controversial due to possible links with development of:
  • Autism.
  • Inflammatory bowel disease, and in particular Crohn's Disease.
• Over 500 million doses of MMR vaccine have been given and rigorous analyis of the evidence to date does not support these putative associations:
  • Neither does the evidence indicate that use of single component vaccines would offer advantages over the combined MMR vaccine.
  • Single component vaccines are not available in the United Kingdom.
    • A doctor in Worcestershire who offered single component measles, mumps or rubella vaccines as alternatives to the combined MMR vaccine has been referred to the General Medical Council and is awaiting a disciplinary hearing.
• In addition to its role in community-wide prevention of measles, mumps and rubella, the MMR vaccine can also have a prophylactic role during an outbreak of measles.
  • If given within 3 days of exposure to the measles virus, MMR vaccine can prevent measles in a previously unvaccinated child.
    • This is because antibodies against the measles component of the vaccine are produced rapidly.
    • By contrast, antibody production to the mumps and rubella components of the vaccine are slow, and MMR vaccination cannot be used to protect against outbreaks of clinical mumps or rubella in the same way.

Measles

• The measles virus is a RNA paramyxovirus that only naturally occurs in humans. There are no animal reservoirs.
• Measles is of direct relevance to the practice of dentistry as:
  • Appropriate Cross Infection practices will reduce the risks of unnecessary spread of measles infections in the dental surgery.
  • Koplik's spots involving the oral mucosa are one of the first clinical manifestations of measles.
• Measles is highly infectious and is spread via aerosols of infected nasopharyngeal secretions.
  • Hence, the need to undertake immunization early in life, and particularly before school is entered.
• Measles can be associated with high morbidity and mortality, particularly in developing countries:
  • Mortality is higher if there is malnutrition. Mortality rates have reached 5-15% in parts of Africa.
  • Measles has killed millions of children around the world in recent decades.

   

Clinical Features of Measles

• Measles is rarely subclinical:
  • The clinical illness nearly always occurs in preschool age children.
• There is an incubation period of 10-14 days.
  • Patients are infectious for approximately 7 days before the rash forms.
• A prodrome ('running before') immediately precedes the rash and is characterised by:
  • Fever, runny nose, conjunctivitis and cough.
  • Koplik's spots - these are pathognomic of measles and should alert the clinician to the illness.
    • Typically involve the buccal and labial mucosa.
    • Irregular, patchy erythema with a central, minute bluish-white specks with the appearance of a 'grains of salt'.
• A morbilliform rash (red and raised) starts 14-18 days after infection.
  • Initially occurs behind the ears and on the forehead and neck.
    • Then spreads over the next 3-4 days to involve the trunk and limbs.
  • The rash can be extensive, with individual lesions becoming confluent.
  • The rash fades after 72 hours, but can leave post-inflammatory pigmentation that may take 6-8 weeks to fade.
  • The patient is no longer infectious once the rash forms.

A. Koplik's spots resemble grains of salt on the oral mucosa and precede the skin rash. B. The rash of measles can be extensive.

• Early complications occur within 18-30 days of infection and include a transient immune supression:
  • This is reasonally tolerated in most children who are otherwise well, but it can be life-threatening in children who are immunocompromised, especially those who are malnurished.
  • The child is at increased risk of other infections such as oral candidosis or Herpes virus infections such as Primary Herpetic Gingivostomatitis.
• Measles is self-limiting in the majority of patients, there is no specific antiviral therapy and management is supportive.
  • However, prompt action is required to limit the number of patients affected by this highly infectious virus. Hence the need for early involvement of the Medical Officer for the Environment.
  • If given within 3 days of exposure to the measles virus, MMR vaccine can prevent measles in a previously unvaccinated child.

Mumps

• The mumps virus is a RNA paramyxovirus that only naturally occurs in humans. There are no animal reservoirs.
• Measles is of direct relevance to the practice of dentistry as:
  • Appropriate Cross Infection practices will reduce the risks of unnecessary spread of mumps infections in the dental surgery.
  • Sialadenitis with associated xerostomia (and an increased risk of secondary bacterial infection) are prominent features.
• Spread occurs via close contact with individuals secreting virus into oropharyngeal secretions.
  • Less infectious than either Measles or Chickenpox (VZV).
  • Infectious for a few days before the onset of clinical symptoms until the salivary gland swelling resolves.

Clinical Features of Mumps

• Infection with mumps virus is often subclinical, especially in children under the age of three.
  • The severity of the clinical illness increases with age.
• There is a incubation period of 14-18 days.
• There may be a fever and the patient feels unwell.
• Salivary gland involvement is a prominent feature of mumps. Salivary gland tissue is inflammed (sialadenitis) and swells with an associated decrease in saliva production. The gland is then at an increased risk of secondary bacterial infection until saliva starts to flow again.
  • Parotid gland involvement (parotitis):
    • Is common (90% bilateral).
    • Is painful due to stretching of the parotid capsule. This lasts for 3-4 days.
    • Displaces the earlobe due to involvement of the tail of the parotid gland.
    • May even cause trismus in extreme instances.
    • May cause the skin overlying the parotid gland to be warm and flushed. However, there is no rash.
  • Clinical swelling of the submandibular glands is much less frequent (10%).
  • Symptomatic sublingual gland involvement is uncommon.
• Mumps can involve a wide range of different tissues and organs:
  • Meningitis is common, but is typically mild.
  • Orchitis may develop 4-5 days after the parotitis:
    • Generally only occurs in post-pubertal males and rarely causes sterility.
  • More serious complications do occasionally occur including:
    • Deafness.
    • Encephalitis.
• Mumps is self-limiting in the majority of patients, there is no specific anti-viral therapy and management is supportive.
  • There should be early involvement of the Medical Officer for the Environment to limit the spread of infection.

Rubella

• The rubella virus is a RNA togavirus that only naturally occurs in humans. There are no animal reservoirs.
• Rubella is of direct relevance to the practice of dentistry as:
  • Appropriate Cross Infection practices will reduce the risks of unnecessary spread of rubella in the dental surgery.
• Rubella (also known as German measles) typically causes a mild clinical illness that includes a erythematous rash.
• However, infection during the first few months of pregnancy can be devastating to the developing foetus:
  • This can result in severe developmental abnormalities with long-term morbidity including hearing loss, mental retardation and cerebral palsy.
  • Similar congenital abnormalities may also follow infection with either Toxoplasmosis, Cytomegalovirus or HSV (ToRCH syndrome, where R is rubella infection).
• Rubella vaccine used to be given as a single vaccine to girls (and not boys) aged 10-14 years old. In an attempt to erradicate rubella from the population, the rubella vaccine is now included in the MMR vaccine used to immunize preschool children (boys and girls).
  • Recent controversies related to the safety of MMR vaccine have undermined this policy and an increase in cases of congenital rubella might be expected in the future.

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