Immune to the facts

摘要

The measles virus is remarkably contagious, infecting more than 95% of susceptible humans exposed to it. About 1 in 1,000 people infected requires hospitalization and may become permanently disabled, and 1 in 300,000 infected with measles develops a progressive neurological disorder, subacute sclerosing panencephalitis, which invariably causes death. But along with smallpox, yellow fever and poliomyelitis, measles is remarkably well controlled by vaccination. Before routine measles vaccination in the United States, some 4,000,000 people a year contracted the disease; widespread vaccination has brought this number down to less than 40. Other countries in which 95% of the population are vaccinated — the proportion believed to provide 'herd immunity', which blocks the transmission of measles—have experienced similar declines in cases. However, coverage in some regions of Africa is less than 50% of the population, and there are still some 40,000,000 infections each yrar, causing more than 600,000 deaths.