What are the ways typhoid fever is transmitted? What are the pathogenesis and pathological characteristics of typhoid fever?

Typhoid bacillus has strong survival ability in nature and is resistant to low temperatures. It can survive in water for 2-3 weeks, last for several months in a frozen environment, survive for 1-2 months in feces, and not only survive for several months in milk, meat, and eggs but can also reproduce. So what are the ways typhoid fever is transmitted? What are the pathological characteristics?

1. Epidemiology of typhoid fever

1. The population is generally susceptible and has lifelong immunity, which is cellular immunity, and reinfection is rare. There is no cross immunity between typhoid and paratyphoid. It is more common in children and young adults, with no gender difference.

2. The disease mostly occurs in summer and autumn, but can be seen all year round.

3. It is common in temperate and tropical areas and is mostly sporadic.

4. Source of infection: patients and chronic carriers: During the incubation period, bacteria are excreted through feces. The amount of bacteria excreted is the highest 2-4 weeks after onset, and the infectiousness is the highest. During the recovery period or after recovery from illness, bacterial excretion decreases. Carriers: those within 3 months are called temporary carriers, those over 3 months are called chronic carriers, and some may excrete the bacteria for life. Chronic carriers are the main source of infection for the continuous spread and epidemic of the disease and have important epidemiological significance.

5. Transmission route: Fecal-oral route: Transmission through the digestive tract. A small part can also be transmitted through extra-gastrointestinal inoculation of microorganisms or infectious materials. Sporadic: Daily contact Epidemic: Food contamination, raw food stalls Outbreak: Water source contamination, sewage

2. Pathogenesis and pathological characteristics

1. Pathogenesis The basic pathological characteristics of typhoid fever: persistent bacteremia and toxemia.

2. Pathological characteristics: Proliferative reaction of the systemic monocyte-macrophage system. The most characteristic lesions are the Peyer's patches and solitary lymphoid follicles in the lower ileum. Week 1: Lymphoid tissue proliferates and swells to form button-like protrusions. Week 2: Necrosis Week 3: Ulcers (easy bleeding, perforation) Week 4: Healing

3. Prognosis of typhoid fever

1. Long-lasting immunity after illness.

2. The prognosis is poor for infants, the elderly, those with malnutrition, and those with obvious anemia.

3. The mortality rate is high among those with serious complications.

4. 3% become chronic carriers.

4. Prevention of Typhoid Fever

1. Control the source of infection and isolate and treat patients as soon as possible. The isolation period should last until 15 days after the clinical symptoms disappear and the body temperature returns to normal. Stool culture tests can also be performed once every 5 to 7 days, and those with two consecutive negative results can be released from isolation. Chronic carriers should be transferred from the above-mentioned jobs, receive treatment, and be regularly supervised and managed. Close contacts must undergo medical observation for 21 days.

2. Cutting off the transmission route is the key measure to prevent this disease. Carry out health education, manage feces, water sources and food hygiene well, and eliminate flies. Develop good hygiene habits, wash hands before meals and after defecation, do not eat unclean food, do not drink raw water or raw milk, etc.

3. Improve the immunity of the population. The Ty21a strain oral attenuated live vaccine was approved for use in the United States in 1989. It has few adverse reactions and has a certain protective effect.