08. Measles Flashcards
Biologic Characteristics and history
Single-stranded RNA virus
Since 2000, due to vaccination, endemic transmission in the U.S. has been interrupted.
Majority of cases now due to importations from another country or linked to importation.
Measles remains a significant public health issue outside of the Americas, including countries in Asia and Europe
Epidemiologic Characteristics (Transmission, Distribution, Reservoir)
Transmission:
- Direct via large respiratory droplets
- Indirect via aerosolized small droplet nuclei: transmission has been documented in closed areas up to 2 hours after area occupied by individual infected with measles
- Can be killed quickly by heat and ultraviolet radiation
Distribution: Global
Reservoir: Humans
Epidemiologic Characteristics (Incubation Period, Infectious Period, Infectivity )
Incubation Period: Approximately 12.5 days (range 7-21 days)
Infectious Period: 4 days before through 4 days after development of rash (typically occurs 14 days following exposure)
Infectivity:
- Measles is one of the most highly contagious infectious agents
- R0 = 12-18
- Transmission commonly occurs among household contacts, school-age children, and healthcare workers
- High level of population immunity required to interrupt measles virus transmission
Clinical Features
Acute respiratory illness
Begins with prodrome characterized by
- Fever – may be as high as 105◦ F
- The three C’s – cough, coryza (runny nose) & conjunctivitis (inflammation of the membrane covering the front of eye and eyelid)
- Koplik’s spots – small white lesions inside the mouth
- Lasts 2-4 days
Followed by onset of rash
- Begins approximately 14 days following exposure and lasts 5-6 days
- Starts on face, then spreads to trunk and limbs •
- Fades in the same order it appeared, from head to extremities
In uncomplicated cases, recovery begins soon after appearance of rash
Complications
30-40% of cases experience complications
Increased risk for those < 5 and > 20 years of age, pregnant females and the immunocompromised
Common complications: Diarrhea, otitis media (ear infection) and pneumonia
Rare complications: Encephalitis (inflammation of the brain), seizures, and death
Case fatality: vary widely depending on ave. age of infection, nutrition status, vaccine coverage and access to health care
Laboratory Diagnosis
Locations where measles is endemic: characteristic clinical features are sensitive/specific enough to base diagnosis upon
Low measles transmission rates: lab diagnosis necessary
- Standard method:d etection of IgG or IgM antibodies to measles virus by enzyme immunoassay (EIA)
- Approx. 80% will be positive at onset of rash / 20% false negatives
- IgM will stay positive for 30+ days following rash onset
Measles Vaccination – U.S.
Currently, only measles vaccine available in U.S. is live, attenuated vaccine, and is in combination with other vaccines.
- MMR – Measles, mumps & rubella MMRV – Measles, mumps, rubella & varicella
Vaccination offers long-term, perhaps life-long immunity
Vaccine contraindications: severe allergic reaction to vaccine component, pregnant, immunocompromised
Vaccine Adverse Reactions
Occur 6 -12 days following vaccination
Fever: most common, 5-15% of recipients
Rash:5% of recipients
Other adverse events: febrile seizure, thrombocytopenia (low platelet count), inflammation of lymph nodes, allergic reaction – are rare
Global Measles Strategic Plan (2012-2020)
9 year plan to address measles control and elimination at the global level
Developed by the Measles Initiative (US CDC / American Red Cross / WHO / United Nations Foundation / UNICEF)
5 core components
- High vaccine coverage
- Effective surveillance
- Outbreak preparedness & response
- Communicate & engage public
- R & D
Suspected Case Investigation
Essential components of case investigation
- Establish a diagnosis of measles
- Obtain immunization history of confirmed cases
- Identify sources of infection
- Assess potential for transmission & identify contacts without evidence of immunity
- Determine importation status
- Obtain specimens for viral culture and isolation
Priority Groups for Contact Investigation
Household
Close contacts other than household
Healthcare settings
Child care centers / schools / colleges
Close settings where defined number of people have congregated (e.g. churches)
Outbreak Control Measures
Isolate case patients for four days post rash onset ‘
Healthcare settings: institute respiratory etiquette and airborne precautions
Postexposure prophylaxis (PEP): preventive treatment started after exposure to a pathogen to decrease risk of infection occurring
- Measles PEP: MMR vaccine & Immunoglobulin (IG)
- Contacts without evidence of immunity should be offered PEP and monitored for signs and symptoms for 1 incubation period
- MMR: administered within 72 hours of exposure; contact may then return to work/daycare/school
- IG: administered within 6 days of exposure; For contacts with contraindications to vaccine (infants < 12 months, pregnant, immunocompromised)
- Special rules for healthcare contacts without evidence of immunity: May not return to work until 21 days after last exposure, regardless of whether PEP received
