March 20, 2025 Author : Saraiva da Cunha (Doenças Infecciosas) Among foodborne and waterbone human infections, those due to bacteria of the genus Salmonella stand out. Salmonella has multiple species and subspecies and the diseases they cause differ , namely their severity. Typhoid fever and paratyphoid fever are among the most serious , have risk of death, and are due, respectively, to the typhi and paratyphi serovars of the bacterium Salmonella enterica , also known for short as Salmonella typhi and Salmonella paratyphi , which cause disease only in humans. According to data from the World Health Organization, these two clinically similar infections, which together are called enteric fever, affected around 9.2 million people worldwide in 2019, causing approximately 110 thousand deaths, most due to Salmonella typhi. In 2019, Salmonella paratyphi was responsible for 3.8 million infections. The European Centre for Disease Prevention and Control (ECDC), in its latest report on typhoid and paratyphoid fever, refers the diagnosis of 54 cases of the disease in Portugal between 2017 and 2021. Typhoid fever is the second most important serious infection in travelers , surpassed only by malaria. Currently, typhoid fever is not common in European countries. It continues to be endemic causing morbidity and mortality in many less developed and poorer regions of the world, affecting both local populations and travelers , mainly in: Sub-Saharan Africa countries S outh and Southwest Asia, such as India, Nepal, Pakistan, Bangladesh, Philippines Middle East Central America, the Caribbean and South America Infection Salmonella is a very resistant bacterium and remains viable in the environment for prolonged periods. It multiplies at temperatures between 7ºC-48ºC, pH between 4.5 and 9.3, it is resistant to freezing temperatures and dry conditions and is destroyed by pasteurization. In both rural and urban areas of endemic countries, the infection occurs orally : Consuming water and food contaminated by feces or urine containing Salmonella typhi and Salmonella paratyphi bacteria due to: Lack of basic sanitation conditions, including waste treatment, sewage systems, supply networks, treatment of drinking water; Poor food preservation and storage conditions; Poor control of insects, especially flies that land on feces and then contaminate food and water. Directly via the fecal-oral route, when hygiene is not adequate . Symptoms, diagnosis and treatment After infection, Salmonella typhi multiplies in the intestine, penetrates its wall and enters the bloodstream, giving rise to a systemic infection. The incubation period (between infection and symptoms occurrence) varies between 6 and 30 days, most commonly 10-14 days. The symptoms of typhoid fever begin gradually and are nonspecific , that is, they are common to many other infections: High fever; Lack of appetite, tiredness and malaise; Abdominal pain and headache; Nausea and vomiting; Febrile convulsions, more important in children; Mild to severe constipation or diarrhea, with or without blood; More rarely, skin rash (in about 25% of patients), cough, muscle pain and throat pain. The suspicion of typhoid fever is raised by symptoms and the patient's context, especially, in the case of travelers, the history of traveling to endemic areas in the last 30 days. The diagnosis can be confirmed by testing the causative bacteria in the blood, feces, urine or material from a skin lesion. Children, elderly and immunocompromised are the main risk groups for infection and more severe disease. In the most severe cases and when treatment for typhoid fever is not started in time, meningitis, peritonitis, intestinal perforation and generalized infection and death may occur. Being a bacterial infection, typhoid fever is treated primarily with antibiotics. In more severe cases, treatment may have to be done in hospital. The increasing antibiotic resistance of Salmonella typhi and Salmonella paratyphi has facilitated the spread of the infection . Recovery from typhoid fever is prolonged, it can take about 2 months. Recovered people can remain carriers of Salmonella for several months and eliminate it through their feces , contributing to maintaining the cycle of infection and the spread of the disease. Therefore, recovered people must reinforce hygiene precautions until they are sure that they no longer pose a risk to others. Prevention For travelers to endemic areas, vaccination against typhoid fever is recommended and is usually prescribed during the traveler's consultation. However, the vaccine does not provide total protection. So, precautions must be taken to avoid consuming potentially contaminated food and wate r, such as: Wash hands with soap and water before eating, drinking or handling food , after using the bathroom, after handling domestic animals or livestock, as well as upon arrival home; Drink only bottled water and open the bottle yourself. Boiling for a few minutes eliminates Salmonella typhi from the water, so it can be considered when bottled water is not available. Another option is to disinfect the water with specific disinfectants available in pharmacies; Do not use ice in drinks unless it is made with bottled water; Do not eat raw vegetables or any foods that are not well cooked and still hot, to ensure they have been cooked recently; Do not drink milk that is not pasteurized or boiled , nor eat any products prepared with unpasteurized milk; Eat only fruits that have peel . Before eating them, you should wash them well with bottled or boiled water and peel them. Never eat the peel; Keep food and drinks covered and in proper storage conditions. People who have returned from traveling to endemic areas in the last 30 days should be alert to symptoms that may be related to typhoid fever and seek medical attention immediately if they occur. Timely medical care is critical to reducing the risk of complications and death. People who have had typhoid fever and recovered should maintain proper hygiene precautions to avoid infecting others and refrain from preparing food for others until they are certain that they are no longer carriers. Sources Autoridade de Segurança Alimentar e Económica. Salmonella . Bhandari J, Thada PK, Hashmi MF, DeVos E. Typhoid fever . Treasure Island: StatPearls Publihing; 2024. European Centre for Disease Prevention and Control. Typhoid and paratyphoid infection. In: ECDC. Annual epidemiological report for 2021. Stockholm: ECDC; 2024. World Health Organization. Typhoid . Meet the infectious diseases clinical team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
