This is notable because typhoid is often said to be a disease of school age children. Indeed, many proponents of vaccination have suggested that vaccination should focus on school age children.

I believe this is because a disproportionate amount of work on typhoid has come out of Chile which has a different epidemiology of typhoid than other places. Most notably Santiago has a good water supply.

The pattern in Karachi are similar to community based data in New Dehli, where children under age 5 years were more than twice as likely to be infected with S typhi than persons 5 – 19 years old.