Can you become infected with salmonella typhi if you already had it once?

Yes, it is possible to become infected with Salmonella typhi again, even if you have had it before. This can happen because immunity to the bacteria may not be long-lasting, and different strains can cause reinfection. Additionally, factors such as poor hygiene, contaminated food or water, and living in or traveling to areas where typhoid fever is common can increase the risk of reinfection.