The total number of untreated polio in the developing countries of the world is probably several million. Measles is a highly contagious infection of the respiratory system caused by the measles virus. About one million children die from measles each year. Even countries that have achieved high levels of measles vaccination coverage and have recorded several years of low incidence frequently have experienced large measles outbreaks. Incidence of measles in North America are believed to be introduced from external sources such as infected persons travelling to North America.
Pertussis is a bacterial infection of the respiratory tract.
Worldwide it is estimated that 200,000 - 300,000 children die each year from pertussis. Diphtheria is a bacterial infection transmitted from person to person through close physical and respiratory contact.