Paratyphoid Fever: Complete ICD-11 Coding Guide (1A08)

1. Introduction

Paratyphoid fever is a systemic infectious disease caused by the gram-negative bacterium Salmonella paratyphi, belonging to the group of enteric fevers. This condition represents a significant challenge for global public health, especially in regions with inadequate basic sanitation and limited access to treated drinking water. Although clinically similar to typhoid fever, paratyphoid fever generally presents a milder course, but is no less important from an epidemiological and clinical perspective.

Transmission of paratyphoid fever occurs predominantly through the fecal-oral route, by ingestion of food or water contaminated with the bacterium. The disease manifests with acute and continuous fever, frequently accompanied by symptoms such as asthenia, abdominal pain, headache, hyporexia, and in some cases, characteristic skin eruptions known as rose spots. The incubation period typically ranges from 6 to 30 days after exposure to the infectious agent.

The importance of correct coding of paratyphoid fever in the ICD-11 system transcends mere statistical classification. Accurate coding enables appropriate epidemiological monitoring, facilitates prevalence and incidence studies, aids in appropriate allocation of public health resources, and contributes to more effective prevention and control strategies. Furthermore, adequate documentation is fundamental for planning sanitary interventions, vaccination programs, and epidemiological surveillance measures in at-risk populations.

2. Correct ICD-11 Code

Code: 1A08

Description: Paratyphoid fever

Parent category: null - Bacterial intestinal infections

Official definition: A condition caused by infection by the gram-negative bacterium Salmonella paratyphi. This condition is characterized by acute and continuous fever. The individual may present with asthenia, abdominal pain, headache, hyporexia, or rash with flat and pink spots. Transmission occurs through ingestion of contaminated food or water. Confirmation is made by identification of Salmonella paratyphi in fecal or blood sample.

Code 1A08 belongs to the chapter of infectious or parasitic diseases of ICD-11, specifically within the category of bacterial intestinal infections. This positioning reflects the nature of the disease as a systemic infection that has its portal of entry through the gastrointestinal tract. The classification recognizes that, although the initial infection occurs in the intestine, paratyphoid fever is a systemic disease with manifestations that go beyond the digestive system, differentiating it from simple bacterial gastroenteritis.

3. When to Use This Code

Code 1A08 should be used in specific clinical scenarios where there is confirmation or strong substantiated suspicion of Salmonella paratyphi infection. Below, we present detailed practical situations:

Scenario 1: Laboratory confirmation by blood culture Patient with persistent fever for 7 days, temperature between 38-40°C, associated with general malaise, frontal headache, and diffuse abdominal pain. Blood culture was performed and isolated Salmonella paratyphi type A. In this case, code 1A08 is definitely appropriate, as there is microbiological confirmation of the etiologic agent through blood sample, as specified in the code definition.

Scenario 2: Identification in stool culture Individual presenting with acute febrile illness lasting 5 days, significant anorexia, marked asthenia, and pasty stools without blood. Stool culture identified growth of Salmonella paratyphi type B. Even without documented bacteremia, identification of the pathogen in fecal sample fully justifies the use of code 1A08.

Scenario 3: Characteristic clinical presentation with suggestive epidemiology Patient with continuous fever for 10 days, appearance of rose-colored spots on the trunk (typhoid roseolas), relative bradycardia, palpable splenomegaly, and history of untreated water consumption in an endemic area. Although awaiting laboratory confirmation, the clinical-epidemiological presentation justifies provisional coding with 1A08, especially if serological testing (Widal) shows elevated titers.

Scenario 4: Documented epidemiological outbreak During investigation of an outbreak in a specific community, patient develops acute and continuous fever, headache, abdominal pain, and generalized malaise. Other cases confirmed laboratorially in the same community were identified as Salmonella paratyphi, with clear epidemiological linkage (same water source). Code 1A08 is appropriate even with laboratory confirmation pending, given the strong epidemiological connection.

Scenario 5: Complicated form with systemic manifestations Patient with confirmed diagnosis of paratyphoid fever who develops complications such as pronounced hepatosplenomegaly, alterations in liver transaminases, and leukopenia. Code 1A08 remains as the primary diagnosis and may be supplemented with additional codes for specific complications.

Scenario 6: Identified convalescent carrier Individual who had confirmed paratyphoid fever 3 months ago and continues to shed Salmonella paratyphi in feces on follow-up examinations, even without active symptoms. Code 1A08 can be used to document the carrier state, important for epidemiological surveillance and public health measures.

4. When NOT to Use This Code

It is essential to recognize situations where code 1A08 should not be applied, even when similar symptoms are present:

Typhoid fever (Salmonella typhi): When microbiological identification confirms Salmonella typhi instead of Salmonella paratyphi, the correct code is not 1A08. Although clinically very similar, they are distinct entities caused by different bacterial serotypes, requiring specific codes.

Gastroenteritis caused by other non-typhoidal Salmonellas: Infections caused by other Salmonella serotypes (such as S. enteritidis or S. typhimurium) that cause predominantly gastroenteric presentations, with watery or dysenteric diarrhea, fever of shorter duration and without the characteristic systemic pattern of enteric fevers, require different coding.

Febrile syndromes of other etiologies: Acute febrile presentations caused by dengue, malaria, leptospirosis or other systemic infections should not be coded as 1A08, even when there are overlapping symptoms such as fever, headache and abdominal pain. Etiological confirmation is essential.

Fever of undetermined origin without confirmation: Patients with prolonged fever under investigation, without microbiological or serological confirmation of Salmonella paratyphi and without clear epidemiological linkage, should not receive code 1A08 prematurely. Codes for fever of undetermined origin are more appropriate until diagnostic clarification.

Intestinal infections caused by other pathogens: Shigellosis, cholera, infections caused by Vibrio, Campylobacter or enterotoxigenic E. coli have their own specific codes and should not be classified as 1A08, even when there is initial diagnostic doubt.

5. Step-by-Step Coding Process

Step 1: Assess diagnostic criteria

The first fundamental step is to confirm whether the patient meets the diagnostic criteria for paratyphoid fever. Ideal confirmation is based on laboratory identification of Salmonella paratyphi in biological samples, preferably blood culture or stool culture. Blood culture shows higher sensitivity in the first week of illness, while stool culture becomes more positive after the second week.

Essential diagnostic instruments include: blood culture (gold standard in the acute phase), stool culture (especially after the first week), serological tests such as the Widal reaction (although with specificity limitations), and molecular methods such as PCR when available. Clinical evaluation should document continuous or plateau fever, symptom duration, presence of characteristic manifestations such as rose spots, relative bradycardia, altered mental status, and organomegaly.

Step 2: Verify specifiers

Paratyphoid fever generally does not require formal severity specifiers in code 1A08, but clinical documentation should record important characteristics. Document the duration of fever (usually 1-3 weeks if untreated), presence or absence of complications (intestinal perforation, gastrointestinal hemorrhage, neurological manifestations), and the specific type of Salmonella paratyphi identified (A, B, or C), although this does not change the main code.

Treatment response and clinical course should also be recorded, including time to defervescence after initiation of appropriate antibiotic therapy, persistence of bacterial shedding in stool (important for identifying chronic carriers), and development of relapses.

Step 3: Differentiate from other codes

1A00 - Cholera: The main difference lies in the predominant clinical presentation. Cholera manifests with profuse watery diarrhea ("rice water"), severe and rapid dehydration, without the pattern of continuous fever characteristic of paratyphoid fever. The etiological agent is Vibrio cholerae, easily differentiated on culture.

1A01 - Intestinal infection by other bacteria of the genus Vibrio: These infections cause acute gastroenteritis, usually self-limited, without the prolonged systemic component. Fever, when present, is of short duration and less intense. There is no pattern of enteric fever with characteristic systemic manifestations.

1A02 - Intestinal infections by Shigella: Shigellosis typically presents with dysentery (diarrhea with blood and mucus), tenesmus, intense colicky abdominal pain, and fever of shorter duration. The presentation is predominantly intestinal, without the prolonged systemic manifestations of paratyphoid fever. Microbiological identification clearly differentiates the two conditions.

Step 4: Required documentation

Adequate documentation should include a complete checklist of information:

Clinical data: Date of symptom onset, fever pattern (continuous, plateau), maximum recorded temperature, associated symptoms (headache, abdominal pain, asthenia, anorexia), presence of rose spots, physical examination findings (hepatosplenomegaly, relative bradycardia).
Laboratory data: Blood culture results with agent identification, stool cultures, complete blood count (common leukopenia), liver function tests, serology when performed, molecular methods if available.
Epidemiological data: History of exposure to potentially contaminated water or food, recent travel to endemic areas, contact with confirmed cases, environmental sanitary conditions.
Course and treatment: Antibiotic therapy instituted, clinical response, time to defervescence, complications developed, need for hospitalization, follow-up tests to verify bacterial shedding.

6. Complete Practical Example

Clinical Case:

A 28-year-old male patient seeks medical care with a complaint of fever for 8 days. He reports that the fever started gradually, becoming continuous, with temperatures between 38.5-39.5°C, without an intermittent pattern. Associated with the febrile condition, he presents with persistent frontal headache, intense generalized malaise, significant loss of appetite, and diffuse abdominal pain. He denies voluminous diarrhea, but reports intestinal constipation over the last 3 days. He reports that 15 days ago he returned from a rural area where he consumed untreated well water.

On physical examination: patient in fair general condition, febrile (axillary temperature 39.2°C), heart rate of 76 bpm (relative bradycardia considering the fever), mucous membranes pink and hydrated. Abdomen slightly distended, diffusely tender on deep palpation, without signs of peritoneal irritation. Liver palpable 2 cm below the right costal margin, spleen palpable at the lower pole. Some pink, flat spots, approximately 2-3 mm in diameter observed on the trunk. Cardiopulmonary auscultation without abnormalities.

Complementary tests ordered: complete blood count revealed leukopenia (3,200/mm³) with relative lymphocytosis, mildly elevated transaminases (AST 78 U/L, ALT 92 U/L). Blood culture collected before initiation of antibiotic therapy. Stool culture also requested. After 48 hours, the microbiology laboratory reports growth of Salmonella paratyphi type A in blood culture.

Step-by-Step Coding:

Analysis of criteria:

Microbiological confirmation: Present - Salmonella paratyphi type A isolated in blood culture, fully meeting the definitive confirmation criterion specified in the code definition.
Characteristic clinical manifestations: Present - acute and continuous fever (8 days), marked asthenia, abdominal pain, headache, anorexia, and rash with pink spots (typhoid rosettes).
Compatible epidemiological history: Present - exposure to potentially contaminated water in a rural area, compatible incubation period (approximately 7 days).
Suggestive physical findings: Present - hepatosplenomegaly, relative bradycardia, typhoid rosettes.
Compatible laboratory profile: Leukopenia with relative lymphocytosis, mild elevation of transaminases, findings frequent in enteric fevers.

Code chosen: 1A08 - Paratyphoid fever

Complete justification:

The code 1A08 is unequivocally the correct code for this case based on multiple converging factors. First, there is definitive laboratory confirmation through the isolation of Salmonella paratyphi in blood culture, which is the diagnostic gold standard and an explicit criterion in the ICD-11 code definition. The clinical presentation is absolutely characteristic of paratyphoid fever, with all cardinal elements present: continuous fever of appropriate duration, systemic symptoms (asthenia, headache, anorexia), abdominal manifestations (pain, hepatosplenomegaly), and the pathognomonic finding of typhoid rosettes.

The epidemiological history reinforces the diagnosis, with clear exposure to a potential source of contamination and a compatible incubation period. The additional laboratory findings (leukopenia, mild hepatic alterations) are consistent with the diagnosis, although not specific. The absence of significant diarrhea does not exclude the diagnosis, as constipation is common in the early phases of enteric fevers, differentiating them from typical bacterial gastroenteritis.

Complementary codes:

In this specific case, there is no need for additional codes, as no documented complications occurred. If the patient had progressed with specific complications (such as intestinal perforation, gastrointestinal hemorrhage, or neurological manifestations), additional codes for these conditions should be added to the primary coding.

7. Related Codes and Differentiation

Within the Same Category:

1A00: Cholera

When to use vs. 1A08: Use 1A00 when there is confirmation of Vibrio cholerae infection, manifesting with characteristic profuse watery diarrhea, severe and rapid dehydration, and rapid progression. Cholera presents a predominantly acute gastroenteric picture, while paratyphoid fever (1A08) is characterized by prolonged systemic fever with more subtle manifestations in the digestive tract.

Main difference: Cholera causes dramatic dehydration from voluminous diarrhea ("rice water" stools), with abrupt onset and rapid course. Paratyphoid fever presents continuous fever as the predominant manifestation, more gradual evolution, and more pronounced systemic picture.

1A01: Intestinal infection by other bacteria of the genus Vibrio

When to use vs. 1A08: Use 1A01 for infections caused by other Vibrio species (V. parahaemolyticus, V. vulnificus), which usually cause acute gastroenteritis, frequently associated with seafood consumption. Use 1A08 specifically when Salmonella paratyphi is identified.

Main difference: Infections by other Vibrio are typically self-limited gastroenteritis of short duration, without the pattern of systemic enteric fever. Paratyphoid fever is a systemic disease with prolonged duration and manifestations beyond the digestive tract.

1A02: Intestinal infections by Shigella

When to use vs. 1A08: Code 1A02 is appropriate when there is confirmation of Shigella (S. dysenteriae, S. flexneri, S. sonnei, S. boydii), typically manifesting as bacillary dysentery with bloody diarrhea, tenesmus, and intense cramping abdominal pain.

Main difference: Shigellosis is characterized by dysentery (blood and mucus in stools), predominantly intestinal symptoms, and shorter duration fever. Paratyphoid fever presents prolonged continuous fever as the central manifestation, frequently with constipation rather than diarrhea in the initial phases.

Differential Diagnoses:

Typhoid fever: Clinically very similar to paratyphoid fever, but caused by Salmonella typhi. Differentiation is essentially microbiological, based on specific identification of the agent. Clinically, typhoid fever may be slightly more severe, but there is significant overlap of manifestations.

Dengue: May present with high fever, headache, abdominal pain, and cutaneous manifestations (petechiae). Distinguished by the presence of intense myalgia, retro-orbital pain, more pronounced leukopenia with thrombocytopenia, absence of significant hepatosplenomegaly, and specific serological confirmation.

Malaria: Presents with fever, may have hepatosplenomegaly, but typically with intermittent fever pattern (tertian or quartan), presence of plasmodium on blood smear, hemolytic anemia, and specific epidemiological history.

8. Differences with ICD-10

In the ICD-10 system, paratyphoid fever was coded as A01.1 to A01.4, with specific subdivisions: A01.1 (Paratyphoid fever A), A01.2 (Paratyphoid fever B), A01.3 (Paratyphoid fever C), and A01.4 (Paratyphoid fever unspecified).

The main change in ICD-11 is the unification under the single code 1A08, without mandatory subdivisions by Salmonella paratyphi type. This simplification reflects ICD-11's approach of reducing unnecessary complexity when subdivisions do not significantly impact clinical management or epidemiological surveillance. Specific identification of the type (A, B, or C) remains clinically important and should be documented in the medical record, but does not require distinct codes.

Another relevant difference is the modified alphanumeric structure of ICD-11, with the code starting with "1A" instead of "A0" from ICD-10. This change is part of the general reorganization of the coding system, allowing greater flexibility for future expansions.

The practical impact of these changes is mainly in the simplification of the coding process, reducing potential errors in selection among subtypes when specific information is not available. For epidemiological surveillance systems that need to track specific types, the information should be captured through additional fields in the registration system, not through distinct codes.

9. Frequently Asked Questions

How is the definitive diagnosis of paratyphoid fever made?

The definitive diagnosis is based on the isolation of Salmonella paratyphi in cultures of biological samples. Blood culture is the method of choice in the first week of illness, with sensitivity of approximately 70-80% when performed before the initiation of antibiotic therapy. Stool culture becomes more sensitive after the second week of illness. Serological methods such as the Widal reaction may be helpful but have limitations in specificity and sensitivity. Molecular techniques such as PCR are increasingly available and offer superior diagnostic speed, although at higher cost.

Is treatment available in public health systems?

Yes, treatment of paratyphoid fever is widely available in public health systems in various countries. First-line antibiotics, such as fluoroquinolones, azithromycin, and third-generation cephalosporins, are generally part of essential medication lists. Outpatient treatment is possible in uncomplicated cases, while severe cases require hospitalization. The typical duration of treatment is 7-14 days, depending on the antibiotic chosen and clinical response. It is important to note that emerging antimicrobial resistance in some regions may influence available therapeutic options.

How long does treatment last and what is the prognosis?

Appropriate antibiotic treatment generally lasts 7 to 14 days. With appropriate antibiotic therapy, fever usually subsides in 3-5 days, although complete recovery may take several weeks. Without treatment, the disease may persist for 3-4 weeks. The prognosis is generally favorable when treatment is instituted early, with a mortality rate of less than 1% in appropriately treated patients. Serious complications such as intestinal perforation or gastrointestinal hemorrhage occur in a small percentage of cases, usually in the third week of untreated illness. Approximately 1-4% of patients may become chronic carriers, shedding the bacteria in feces for more than one year.

Can this code be used in medical certificates and notifications?

Yes, code 1A08 should be used in medical certificates when appropriate, although it is often preferable to use descriptive terminology for documents intended for patients or employers. For epidemiological surveillance notifications, the use of the ICD-11 code is essential, as paratyphoid fever is a notifiable disease in many countries due to its importance in public health. Appropriate notification allows for outbreak tracking, identification of contamination sources, and implementation of control measures. Accurate documentation is also essential for reimbursement purposes in health systems based on diagnostic codes.

What is the difference between typhoid fever and paratyphoid fever in clinical practice?

Clinically, the two conditions are very similar, presenting with continuous fever, systemic symptoms, and abdominal manifestations. Paratyphoid fever tends to be slightly milder, with lower incidence of serious complications, although there is considerable overlap. The definitive distinction is microbiological: typhoid fever is caused by Salmonella typhi, while paratyphoid fever is caused by Salmonella paratyphi (types A, B, or C). Both require the same type of diagnostic investigation and similar therapeutic approach. Differentiation is important mainly for epidemiological purposes, surveillance, and development of vaccination strategies, since available vaccines for typhoid fever do not provide protection against paratyphoid fever.

Can people who have had paratyphoid fever transmit the disease after recovery?

Yes, some individuals may become carriers after clinical recovery, continuing to shed Salmonella paratyphi in feces. Convalescent carriers shed the bacteria for up to 3 months after acute infection, while chronic carriers (more rare) may shed for more than one year. This has important public health implications, especially for people who work with food handling. Follow-up stool culture examinations are recommended after completion of treatment to document bacterial clearance. Chronic carriers may require prolonged antibiotic treatment or, in refractory cases, even cholecystectomy, since the gallbladder is the main site of chronic colonization.

Is there a vaccine available for paratyphoid fever?

Currently, there is no specific vaccine widely available exclusively for paratyphoid fever, unlike typhoid fever, for which effective vaccines exist. Some conjugate vaccines in development promise protection against multiple Salmonella serotypes, including S. paratyphi, but are not yet commercially available. Prevention of paratyphoid fever is based mainly on basic sanitation measures, adequate water treatment, food and personal hygiene. For travelers to endemic areas, strict attention to the quality of water and food consumed is recommended, avoiding untreated water, raw or undercooked foods, and foods from street vendors.

How to differentiate paratyphoid fever from other causes of prolonged fever?

Differentiation requires a systematic approach considering detailed clinical history (including travel, food exposures), complete physical examination, and appropriate laboratory investigation. Characteristics suggesting paratyphoid fever include: continuous fever with gradual onset, history of exposure to potentially contaminated water or food, presence of rose spots, hepatosplenomegaly, relative bradycardia, and leukopenia. Other causes of prolonged fever such as tuberculosis, endocarditis, autoimmune diseases, and neoplasms usually present with distinct characteristics. Investigation should include blood cultures, stool cultures, complete blood count, liver function tests, and, depending on epidemiological context, tests for malaria, dengue, leptospirosis, and other endemic infections. Microbiological confirmation remains essential for definitive diagnosis.

Conclusion:

Appropriate coding of paratyphoid fever with ICD-11 code 1A08 is fundamental for appropriate clinical management, effective epidemiological surveillance, and public health planning. Understanding when to use this code, differentiating it from similar conditions, and appropriately documenting all clinical and laboratory aspects are essential competencies for health professionals. Paratyphoid fever remains an important public health problem in many regions, and accurate coding contributes significantly to control and prevention efforts for this preventable disease through adequate sanitary measures.

External References

This article was prepared based on reliable scientific sources:

References verified on 2026-02-04

Paratyphoid fever

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