High fever for 7 days with one episode of loose stool . Low saturation

High fever for 7 days with one episode of loose stool . Low saturation of oxygen with pr 90 lower abdomen pain . History of same symptoms amongst family members and neighbours. No rashes no history of cough and cold. I am thinking of shigelosis what are other possible differential diagnosis

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Here is a structured differential diagnosis analysis for this clinical presentation:

Clinical Summary

Key features to anchor the differential:

Fever x 7 days (prolonged, high-grade)
Low oxygen saturation (SpO2 reduced, PR 90)
Lower abdominal pain
Only one episode of loose stool (not frank dysentery)
Cluster pattern: family members and neighbours affected (point-source or waterborne/foodborne outbreak)
No rash, no cough or cold

Why Shigellosis Is a Differential - But Less Likely as the Primary Diagnosis

Shigellosis classically presents with dysentery - bloody mucoid diarrhea, tenesmus, and colicky lower abdominal pain. The fever averages 48 hours before diarrhea onset. Per Sleisenger & Fordtran, the average symptom duration in adults is ~7 days; dysentery is present in >80% of S. dysenteriae cases. Only one episode of loose stool in 7 days of high fever makes typical shigellosis unlikely - though atypical/mild shigellosis (especially S. sonnei) with predominantly systemic features is possible.

The cluster pattern (family + neighbours) fits shigellosis, but also fits several other waterborne/foodborne illnesses.

Low oxygen saturation is not a typical feature of shigellosis and should prompt consideration of other diagnoses.

Differential Diagnoses (Ranked by Fit)

1. Typhoid Fever (Enteric Fever) - TOP DIFFERENTIAL

This is actually the most likely diagnosis here. Key features supporting it:

Feature in Patient	Typhoid Fit
High fever x 7 days	Classic - fever rises stepwise over 1-3 weeks
Only mild/single episode of diarrhea	Typhoid is systemic, not primarily a diarrheal illness; 30% have constipation
Lower abdominal pain	Classic (ileal lymphoid involvement)
Cluster in family/community	Waterborne/fecal-oral point-source outbreaks typical
No rash	Rose spots appear in only ~30% and mainly in fair-skinned; absent in most dark-skinned patients
Low SpO2	Pulmonary complications (pneumonia, myocarditis, septic shock) can occur as typhoid progresses

Per Tintinalli's Emergency Medicine: "Once malaria is excluded, typhoid fever is commonly the cause of a febrile illness lasting >10 days... Typhoid fever classically begins with fever and headache and then progresses to high fever with chills, headache, cough, abdominal distention, myalgias, constipation, and prostration. 30% of patients present with constipation rather than diarrhea."

The low SpO2 may indicate typhoid pneumonitis, myocarditis, or early sepsis - all recognized complications.

2. Malaria (Plasmodium falciparum / vivax) - MUST EXCLUDE FIRST

Prolonged fever in an endemic area is malaria until proven otherwise
Cluster pattern fits (common mosquito source)
Lower abdominal pain, prostration, and low SpO2 (in P. falciparum - severe malaria) all fit
No diarrhea or rash is consistent with malaria
The absence of rash and cough makes malaria very plausible
P. falciparum can cause respiratory distress (low SpO2) via pulmonary edema

3. Leptospirosis

Waterborne illness affecting clusters (flooding, sewage contamination)
Presents with high fever, myalgia, headache, abdominal pain
Can affect lungs causing pulmonary hemorrhage syndrome (explains low SpO2)
Typically no significant diarrhea
Jaundice, conjunctival suffusion, renal failure in severe forms (Weil's disease)
Community clustering fits after shared water exposure

4. Viral Hemorrhagic Fever (e.g., Dengue, Chikungunya)

Dengue: high fever, severe headache, myalgia, abdominal pain, no rash in early phase (rash appears after fever spikes)
Community clustering fits (Aedes mosquito)
However, dengue classically causes thrombocytopenia and leukopenia, not typically prolonged 7-day fever with low SpO2 alone
Ebola/other hemorrhagic fevers: consider in endemic areas with clusters

5. Entamoeba histolytica (Amoebic Colitis / Amoebic Liver Abscess)

Fecal-oral transmission, clusters possible with contaminated water/food
Lower abdominal pain, loose stool
Amoebic liver abscess: high swinging fever, right upper/lower quadrant pain, can persist for weeks, SpO2 can drop if abscess is large (causing diaphragm elevation and basal lung compression)
No rash, no cough directly
The clustering pattern and poor sanitation fit perfectly

6. Salmonella Gastroenteritis (Non-typhoidal)

Subacute onset of fever, nausea, diarrhea (watery, 6-8 motions/day)
Fever and nausea resolve in 1-2 days but diarrhea persists 5-7 days
High fever possible, though typically shorter course than 7 days
Bacteremia occurs in ~5%, which could explain the systemic presentation

7. Brucellosis

Undulant fever lasting weeks, fatigue, myalgia, lower abdominal/back pain
Community clustering fits (shared food source - raw dairy, meat)
No rash in most cases
Hepatosplenomegaly, leukopenia
Low SpO2 less typical unless pulmonary brucellosis

8. Rickettsial Disease (Typhus - Scrub or Murine)

Scrub typhus: fever for 7+ days, headache, eschar (may be missed), no rash visible early
Murine typhus: similar presentation, rat flea exposure
Low SpO2 possible (interstitial pneumonitis)
Eschar (small ulcer at bite site) may be overlooked
Community clustering fits if shared vector exposure
Important: rash of typhus may be absent or subtle in early disease; "no rash" does not exclude typhus

9. Viral Hepatitis (Hepatitis A or E)

Hepatitis A/E: fecal-oral spread, classic community clusters
Prodrome: fever, abdominal pain (right upper quadrant predominantly), malaise
Diarrhea can occur
Jaundice may not yet appear in early presentation
Low SpO2 less typical unless fulminant hepatic failure

10. Campylobacter / Yersinia Enterocolitis

Fever, abdominal pain, diarrhea
Yersinia: can mimic appendicitis with right iliac fossa pain (mesenteric adenitis), can have prolonged fever
Campylobacter: usually bloody diarrhea, shorter course
Less likely to cause community clustering of this scale

Feature That Demands Urgent Attention: Low SpO2

Low oxygen saturation is not explained by simple gastroenteritis or shigellosis. This points to:

Severe/complicated typhoid (myocarditis, pneumonia, septic shock)
Severe falciparum malaria (ARDS, pulmonary edema)
Leptospirosis with pulmonary hemorrhage
Amoebic abscess with pleural involvement
Scrub typhus with interstitial pneumonia

Recommended Workup Priority

Thick and thin blood film + RDT for malaria - STAT (exclude first)
Blood culture x 2 (typhoid diagnosis, sensitivity ~60-80% in week 1)
Widal test / Typhidot (typhoid serology - limited specificity but useful in context)
CBC: leukopenia with relative lymphocytosis → typhoid; thrombocytopenia → malaria/dengue
LFTs (elevated in typhoid, hepatitis, leptospirosis)
Stool microscopy + culture
Dengue NS1 Ag / IgM if clinically suspected
Leptospira serology if cluster history suggests water exposure
Chest X-ray to evaluate low SpO2 source
Abdominal ultrasound for hepatosplenomegaly/liver abscess

Summary Table

Diagnosis	Fever	Diarrhea	Abdominal Pain	Low SpO2	Cluster	No Rash
Typhoid	+++	Minimal/absent	++	Possible (severe)	++	++ (rose spots rare)
Malaria	+++	-	+	++ (falciparum)	+	++
Shigellosis	++	+++ (bloody)	++	Rare	++	+
Leptospirosis	+++	-	+	++	+	+
Amoebic abscess	+++	+ (mild)	++	Possible	+	++
Rickettsial	+++	-	+	++	+	Rash late/absent
Dengue	+++	-	+	+	++	Rash variable

Bottom line: Typhoid fever is the single most fitting diagnosis and should be your primary working diagnosis. Malaria must be excluded by blood film as the first step. The cluster pattern, 7-day high fever, minimal diarrhea, lower abdominal pain, and no rash are a textbook enteric fever picture. The low SpO2 signals possible complications requiring urgent assessment.

Sources: Tintinalli's Emergency Medicine (Comprehensive Study); Sleisenger & Fordtran's Gastrointestinal and Liver Disease; Goldman-Cecil Medicine; Symptom to Diagnosis (4th Ed)

Pt has history of appendectomy and bp is also low

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