Typhoid: Salmonella typhi, Symptoms and the Widal Test
Biology · Human Health and Diseases · NEET
Typhoid fever is caused by a bacterium called Salmonella typhi. It spreads through food and water that are contaminated, and it is confirmed by the Widal test. Memory hook: "Sal + Widal" - Salmonella causes it, Widal confirms it.
Typhoid flow for NEET: Salmonella typhi enters the small intestine through contaminated food and water, spreads through blood, causes high fever and stomach problems, and is confirmed by the Widal test.
Your doubts, answered
What is the causative agent of typhoid fever?
The causative agent of typhoid is Salmonella typhi. It is a pathogenic (disease-causing) bacterium. NEET often asks this as a direct match, so remember the exact name: Salmonella typhi.
Which test confirms typhoid? Is it the Widal test?
Yes. Typhoid fever is confirmed by the Widal test. This is the one test name NCERT gives for typhoid, so link them together: typhoid to Widal test. Anthrone test and UTI test are wrong options NTA uses as traps.
Is typhoid a bacterial or viral disease?
Typhoid is a bacterial disease. The bacterium is Salmonella typhi. This matters for NEET because many matching questions ask you to group diseases by pathogen type. Do not confuse it with viral diseases like common cold.
How does Salmonella typhi enter and spread in the body?
The bacteria enter the small intestine through food and water contaminated with them. From there they migrate to other organs through the blood. This is why typhoid is a water-borne and food-borne disease.
What are the main symptoms of typhoid?
The symptoms are sustained high fever (39 to 40 degree C), weakness, stomach pain, constipation, headache and loss of appetite. In severe cases, intestinal perforation and death may occur.
Who was Typhoid Mary?
Mary Mallon, nicknamed Typhoid Mary, was a cook who was a typhoid carrier. She kept spreading typhoid for several years through the food she prepared. NCERT gives her as a classic example of a carrier.
⚠️ The NEET trap ✗ Salmonella typhi / Anthrone test ✓ Salmonella typhi / Widal test 🧠 The pathogen name Salmonella typhi is correct, so students relax and pick the wrong test. The Anthrone test is a sugar test, not for typhoid. Only the Widal test confirms typhoid. Always check BOTH halves of a pair before choosing.
Real NEET questions
NEET 2019
Identify the correct pair representing the causative agent of typhoid fever and the confirmatory test for typhoid.
A · Plasmodium vivax / UTI test
B · Streptococcus pneumoniae / Widal test
C · Salmonella typhi / Anthrone test
D · Salmonella typhi / Widal test ✓
Solution: Typhoid fever is caused by the pathogenic bacterium Salmonella typhi, and the disease is confirmed by the Widal test. Plasmodium causes malaria and Streptococcus pneumoniae causes pneumonia, so their pairs are wrong. The Anthrone test and UTI test are not confirmatory tests for typhoid.
NEET 2024
Match List I with List II: A. Common cold, B. Haemozoin, C. Widal test, D. Allergy | I. Plasmodium, II. Typhoid, III. Rhinoviruses, IV. Dust mites. Choose the correct answer.
A · A-I, B-III, C-II, D-IV
B · A-III, B-I, C-II, D-IV ✓
C · A-IV, B-II, C-III, D-I
D · A-II, B-IV, C-III, D-I
Solution: Common cold is caused by Rhinoviruses (A-III). Haemozoin is the toxic substance from Plasmodium (B-I). The Widal test diagnoses typhoid (C-II). Allergy is triggered by dust mites (D-IV). So the correct match is A-III, B-I, C-II, D-IV.
NEET 2020
Match the diseases with the causative organism: (a) Typhoid (b) Pneumonia (c) Filariasis (d) Malaria | (i) Wucheria (ii) Plasmodium (iii) Salmonella (iv) Haemophilus.
A · (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
B · (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
C · (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
D · (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii) ✓
Solution: Typhoid is caused by Salmonella (a-iii), Pneumonia by Haemophilus (b-iv), Filariasis by Wuchereria (c-i) and Malaria by Plasmodium (d-ii). This gives a-iii, b-iv, c-i, d-ii.
Solved Human Health and Diseases NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Salmonella typhi, a pathogenic bacterium. It is the single most-asked fact about typhoid in NEET.
What confirms typhoid fever?
The Widal test confirms typhoid fever. Remember typhoid goes with the Widal test.
What is the body temperature in typhoid?
Typhoid causes a sustained high fever of 39 to 40 degree C. NCERT gives this exact range.
Which organ does Salmonella typhi first enter?
It enters the small intestine through contaminated food and water, then spreads to other organs through the blood.
What can happen in severe typhoid?
In severe cases, intestinal perforation and death may occur. This shows why typhoid must be treated early.
Why is typhoid a food-borne disease?
Because the bacteria enter the body through food and water contaminated with them. A carrier like Typhoid Mary can spread it through food she prepares.
