Typhoid is a dangerous disease caused by the bacterium Salmonella typhi. According to the National Institutes of Health, typhoid cases are rare in the United States: only about 400 cases occur each year, and 75 percent of these are acquired during travel to countries where typhoid is common 1. People who have been infected with typhoid fever in the past may experience a relapse due to several factors.

Ineffective Treatment

The Centers for Diseases Control and Prevention states that typhoid is treated using antibiotics. According to the National Institutes of Health, symptoms of typhoid may return if treatment is not completed 1. Patients who fail to complete the full course of antibiotic treatment may develop antibiotic resistance which requires stronger antibiotics. Patients should ensure that they complete taking all the doses of antibiotics prescribed for typhoid even if they begin to feel better within a few days of taking these drugs.

Vaccine Ineffectiveness

According to the Centers for Diseases Control and Prevention, typhoid vaccines are used to prevent typhoid infection and are recommended for people who travel regularly to countries where typhoid is common. Typhoid vaccines are not 100 percent effective, and patients who fail to observe other preventative measures may become reinfected with typhoid fever. Typhoid vaccines become ineffective after several years, and people at risk require boosters every two years for inactivated vaccines, and every fives years for live oral typhoid vaccines.

Typhoid Carrier

According to Centers for Diseases Control and Prevention, some people who recover from typhoid illness may continue to carry the bacteria in their bloodstream and body organs. These people are called typhoid carriers, and they continue to shed Salmonella typhi in their feces and urine. Typhoid carriers are more likely to have typhoid fever relapse because the Salmonella typhi is already present in their bodies. Typhoid carriers who contaminate food may become reinfected with typhoid if they ingest the food.