Childhood infection and adult disease.

In England and Wales there is a strong geographical relation between current mortality from chronic bronchitis and emphysema in adults and infant mortality from bronchitis and pneumonia 50 years ago. Follow-up studies of infants and children show that certain pulmonary infections cause persisting abnormalities of lung function. This suggests that infection of an organ system during a period of rapid growth may have permanent deleterious effects. Long-term consequences of infection may also depend on age-related differences in the host response. The relationship between age of infection with hepatitis B virus and the likelihood of becoming a chronic HBsAg carrier is an example of this. Evidence that the common communicable diseases of childhood tend to have occurred late in cases of multiple sclerosis hints at similar mechanisms in this disease. The current patterns of motor neuron disease mirror the epidemiology of poliovirus infection 40 years ago both in geographical distribution and in changes over time. The same neuronal populations are affected in both these conditions; is there a causal link?