Children are more at risk for contracting typhoid fever, according to Mayo Clinic, but their symptoms tend to be milder than those of adults. Typhoid complications in children are rare, claims KidsHealth, and they tend to involve the gastrointestinal tract. Still, a child can become dangerously ill due to dehydration or a perforated bowel.
Another notorious fact about typhoid is that some people are carriers, says Huffington Post, KidsHealth and Mayo Clinic. They carry the bacteria, which is a type of salmonella, but do not get sick themselves. One of the most famous cases was an Irish immigrant called Mary Mallon, who harbored the bacteria, spread it around via her work as a cook but never got sick. Some people are carriers for decades.
Researchers have discovered that the reason for this is because for some people the bacteria hides in the macrophages in their immune systems, says Huffington Post. The bacteria keep the macrophages from eating and destroying them, but still manage to be passed on from the infected person to another. In the meantime, the bacteria replicates by using a protein called PPAR-delta. It probably stimulates the macrophage itself into producing this protein. About 3 to 5 percent of patients who have had typhoid become carriers after they recover, says MedicineNet.