Resurgent diphtheria--are we safe?

Diphtheria, one of the major causes of morbidity and mortality in the past, seemed nearly eliminated from industrialized countries, thanks to improved hygienic conditions and large scale vaccinations. In 1990, a large epidemic started in Eastern Europe, mainly in Russia and Ukraine, with over 70,000 cases reported within a 5 year period. The main factors leading to the epidemic included low immunization coverage among infants and children, waning immunity to diphtheria among adults, and profound social changes in the former Soviet Union. The possibility of new virulence factors in the epidemic strain has not yet been ruled out. Even though immunity among adults is far from complete in Western Europe, the epidemic did not spread there. The main reason for this might be the good immune status of children and lack of social turbulence favouring the spread of infection. Several countries have also taken preventive measures, which may also have played a role in protection against the potential epidemic.