Measles outbreaks in Micronesia, 1991 to 1994

Area of Science:

• Epidemiology
• Public Health
• Infectious Disease Dynamics

Background:

• Multiple Micronesian islands faced significant measles outbreaks between 1991-1994.
• These outbreaks occurred after a 20-year period with no reported measles cases on most islands.

Purpose of the Study:

• To characterize the epidemiology of measles outbreaks in Micronesia.
• To identify transmission sources and assess the effectiveness of control measures.

Main Methods:

• Reviewed measles surveillance data, hospital records, and death certificates.
• Assessed pre-outbreak vaccination coverage using public health records.
• Conducted genetic sequencing of viral isolates and epidemiological investigations.
• Utilized linear regression to evaluate outbreak control strategies.

Main Results:

• Over 1300 cases and 16 deaths were reported from 1991-1994.
• Pre-outbreak vaccination coverage varied from 55% to 94% among 2-year-olds.
• Genetic and epidemiological data indicated inter-island transmission and external importations.
• Highest attack rates were observed in children under 5 and adolescents aged 10-19.
• Higher 2-dose vaccination coverage in ages 5-9 correlated with lower attack rates (P < 0.001).
• Rapid mass vaccination campaigns significantly shortened outbreak durations (P = 0.049).

Conclusions:

• Island populations are highly susceptible to measles, necessitating high two-dose vaccination coverage.
• Prompt and widespread measles vaccination campaigns proved effective in controlling island outbreaks.
• Enhanced public health infrastructure and surveillance are crucial for early detection and rapid response to outbreaks.