The infant and young child during periods of acute infection.
Passive immunity, which is conferred on infants through maternal antibodies and breast milk, helps to protect them against infection during the first months of life. Later, as this immunity decreases and contact with the environment increases, the incidence of infections rises rapidly and persists at a high level during the second and third years of life. Infections and inadequate diet may be of little consequence for the well-nourished child; in underweight children, however, each episode of infection is frequently more protracted and has a considerably greater impact on health. Besides the reduced food intake and absorption, the demand for nutrients is higher during periods of infectious diseases. Infants who are exclusively breast-fed are at much lower risk from diarrhoeal diseases. In contrast, bottle-fed infants and children receiving foods other than milk, particularly in an unsanitary environment, are at much greater risk of infection from contaminated food and utensils. The period of convalescence from diarrhoeal and other disease is characterized by the return of a normal appetite and increased nutritional requirements to permit catch-up growth and the replenishment of nutritional reserves. A primary requirement is that children receive sufficient dietary energy and nutrients to enable them to achieve their growth potential.