Paratyphoid fever: causes, symptoms, diagnosis, treatment, and prognosis

Paratyphoid fever A, B, and C are acute infectious diseases caused by Salmonella Paratyphi A, Salmonella Paratyphi B, and Salmonella Paratyphi C, respectively. The symptoms of paratyphoid fever A and B are similar to those of typhoid fever, generally mild, and short duration and low mortality are present. Paratyphoid fever C has different symptoms, and can be manifested by mild typhoid fever, acute gastroenteritis, or septicemia.


There are 3 serovars of Salmonella Paratyphi including Salmonella Paratyphi A, Salmonella Paratyphi B, and Salmonella Paratyphi C. They all have O antigen and H antigen, and Salmonella Paratyphi C has Vi antigen. Under natural conditions, Salmonella Paratyphi can only infect humans.

The source of infection is patients and carriers. The mode of transmission is roughly the same as that of typhoid fever, but food transmission is more common, because Salmonella Paratyphi can survive in foods for a long time. Paratyphoid fever B is seen all over the world, paratyphoid fever A is more localized, and paratyphoid fever C is less common.


The pathological changes of paratyphoid fever A and B are almost the same as those of typhoid fever, but the intestinal lesions of patients with gastroenteritis are significant and extensive, and the colon is often invaded. Intestinal lesions in paratyphoid C are not significant, and there may be no ulceration in the intestinal wall, but focal suppurative lesions may occur in other areas such as joints, cartilage, pleura, and pericardium.

Signs and Symptoms

The incubation period is shorter than that of typhoid fever, usually 8 - 10 days, sometimes only 3 - 6 days.

Paratyphoid fever A and B present mostly slow onset, rarely sudden onset. The initial symptoms are symptoms of acute gastroenteritis, such as abdominal pain, vomiting, and diarrhea. About 2 - 3 days after onset, the symptoms are relieved. Subsequently, the body temperature rises, and typhoid symptoms appear. Significant symptoms of gastroenteritis may be present and are more common in paratyphoid fever B. Fever often reaches a peak in 3 - 4 days, and large fluctuations are present. Continuous fever is less common. Fever has a short duration of averagely 3 weeks in paratyphoid fever A and 2 weeks in paratyphoid fever B. Mild septicemia and significant intestinal symptoms are present. Relative bradycardia and hepatosplenomegaly may occur, which are the same as those of typhoid fever. The skin lesions often appears early, and can spread throughout the whole body and may be slightly larger in size and darker in color than those of typhoid fever. Recurrence and recrudescence are more common in paratyphoid fever A and B, especially in paratyphoid fever A. Intestinal hemorrhage and intestinal perforation are rare. Low mortality rate is present.

Paratyphoid fever C may be manifested by typhoid fever, acute gastroenteritis, and septicemia.

Typhoid fever

Symptoms are similar to those of paratyphoid A and B. Sudden onset, rapid hyperthermia, irregular fever, chills, headache, and generalized muscle ache and weakness are present. Convulsions or dysphoria can be seen in children, and deliration or coma can occur in severe patients. Hepatosplenomegaly is present, and may be accompanied by jaundice and liver dysfunction. Fever persists for about 1 - 2 weeks. Subsequently, fever gradually drops, the condition tends to improve.

Acute gastroenteritis

Acute gastroenteritis is caused mostly by ingestion of foods contaminated by the bacteria. Gastrointestinal symptoms, short duration, and recovery within 2 - 5 days are present.


Septicemia is more common in frail children and patients with chronic wasting disease. Sudden onset, chills, high fever, irregular, remittent, or intermittent fever, and 1 - 3 weeks of fever are present. If there are suppurative complications, the duration of disease is longer. Skin lesions and hepatosplenomegaly are present, and jaundice may occur.

More than half of patients may have protracted suppurative complications as follows.

Arthropathy often occurs in the costal cartilage, ribs, clavicle, knee, ankle, foot, finger, lumbar vertebra, and sacrum, and then focal abscess occurs. The abscess is only mildly red and swollen, and sinus tracts are formed after rupture of the abscess in few weeks, which affect the adjacent bones, causing osteomyelitis. The abscess can also last for several months without rupture, and the appearance resembles tuberculous infection, but Salmonella Paratyphi C can be found in the pus culture.

Most patients present with bronchitis, pneumonia, pleural effusion, and empyema, and sometimes the bacteria can be detected in the sputum culture.

Purulent meningitis, endocarditis, pericarditis, and pyelonephritis also occasionally occur.


Sometimes, it is not easy to differentiate the disease from typhoid fever, and diagnosis is usually based on the results of bacterial culture and Widal test.


Currently, the recommended antibacterial medications are mainly quinolones and third-generation cephalosporins.

Quinolones, such as ciprofloxacin, ofloxacin, and norfloxacin, have a strong antibacterial effect against Salmonella including chloramphenicol-resistant strains, and should be preferred. However, children and pregnant women are contraindicated. The treatment regimen is ofloxacin 200mg orally 3 times a day, or ciprofloxacin 250 - 500mg/d intravenously or 250mg orally 3 times a day, or norfloxacin 400mg orally 3 times or 4 times a day, until 10 days to 2 weeks after body temperature drops to normal.

Third-generation cephalosporins, especially ceftriaxone, cefoperazone, and ceftazidime, have strong antibacterial effects. The dose is 2 - 4g/d intravenously for 2 weeks.

Chloramphenicol can still be used, and the dose is 1.5 - 2g/d orally, until fever drops, and then halved dose for 10 - 15 days.

Amoxicillin 2 - 4g/d orally for 2 - 3 weeks has a certain effect against non-resistant bacterial strains.

Patients with obvious septicemia can use hormones in combination with a sufficient amount of effective antibacterial medications. The treat regimen is prednisone 5mg orally 3 times a day or 4 times a day, or dexamethasone 2 - 4mg intravenously once a day, for less than 3 days. For patients with significant tympanites or diarrhea, the use of hormones should be cautious to avoid intestinal hemorrhage and intestinal perforation.


Because paratyphoid fever is milder than typhoid fever, intestinal hemorrhage and intestinal perforation are less common, the prognosis is better. However, paratyphoid fever C can cause osteomyelitis and multiple abscesses in the body cavity or tissue, which should be cautious.