FACTORS INFLUENCING THE SPREAD OF BETA HEMOLYTIC STREPTOCOCCAL INFECTIONS WITHIN THE FAMILY GROUP

Abstract

From this study the following conclusions can be drawn about the spread of streptococcal disease:

Approximately one-half to one-fourth of sibling contacts will develop streptococcal infection.

Less than 1 in 20 of the parents will develop streptococcal infection from a sick child.

Although in larger families there were more secondary attacks than in smaller families, the number of such attacks was roughly proportional to the number exposed, and the secondary attack rate in individuals was no higher than in smaller families.

Although the age of the primary case bore little relation to the attack rate in siblings, the age of the exposed children did seem related. Those under 2 years of age and those over 10 were least frequently attacked while the 3-and 4-year-ld children seemed most susceptible.

Cases of otitis media in the primary case seemed to be associated with a higher attack rate in siblings than any other clinical manifestation of disease.

Delay in treatment of the primary case beyond 2 days was associated with a rapidly increasing attack rate in sibling contacts.

Of the types of Group A streptococci which caused disease in the period studied, type 3 was associated with a much higher attack rate in siblings than other types.

Approximately half of the "secondary" cases occurred simultaneously, prior to, or more than 5 days after the onset of illness in the case which the physician was called to treat.