This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax firstname.lastname@example.org with numerous contributions by others.
Measles is one of the most contagious infectious diseases. "A child
can catch measles by breathing the air in a doctor's waiting room two
hours after an infected child has left." (Fettner) 90% of susceptible
household contacts get the disease (Harrison). Measles spreads very
rapidly in unexposed populations. In 1951, it was introduced to
Greenland by a recently arriaved visitor who went to a dance as he was
coming down with it, and in three months it spread to more than 4000
cases and 72 deaths. The attack rate was 999 cases per 1000
people. In 1875, measles was introduced to Fiji and killed 30 percent
of the population (Smith).
In areas where it was endemic, before the measles vaccine, measles
epidemics used to occur at regular intervals of two to three years,
usually in the spring, with small local outbreaks in intervening
years. Mortality is low in healthy, well-nourished children unless
complications ensue (Merck), but nevertheless there were 400 deaths a
year before an improved measles vaccine was introduced in 1966
(Pantell, Fries, and Vickery). Complications include brain infection,
pneumonia, convulsions, blindness, various bacterial infections,
encephalitis, and SSPE (a fatal complication which can occur years
after a person has had measles). Pregnant women who get measles have a
20% chance of miscarriage.
Worldwide, measles is one of the leading causes of childhood
mortality. "Measles has been called the greatest killer of children in
history." (Clements, Strassburg, Cutts, and Torel) In 1990, "45
million cases and around 1 million deaths were estimated to occur in
developing countries. Thus measles is still responsible for more
deaths than any other EPI target diseases. The true number dying as a
result of measles may be twice the estimated 1 million if the recently
documented delayed effect of the disease is taken into account."
(Ibid.) Mortality is higher in developing countries due to a
difference in the age at which most people catch it (measles is a more
dangerous disease in the very young), poorer nutrition, less
availability of treatment for bacterial chest infections, and other
environmental factors. However, "Even in countries with adequate
health care and healthy child populations, the complication rate can
reach 10%." (Ibid.)
More information on the incidence of measles complications is found in
the answer to Q3c.2.