General Medicine
Fever and Tropical Infections
Fever and tropical infections for MBBS: malaria, dengue, typhoid and sepsis, the peripheral smear and fever of unknown origin, mapped to NMC codes IM4.1 to IM4.15.
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Fever and Tropical Infections
Fever and tropical infections for MBBS: malaria, dengue, typhoid and sepsis, the peripheral smear and fever of unknown origin, mapped to NMC codes IM4.1 to IM4.15.
This chapter builds a systematic approach to the febrile patient in the Indian setting, covering the physiology of fever and the major tropical infections. It emphasises the peripheral smear for malaria, dengue warning signs, recognition of sepsis and the workup of fever of unknown origin.
High-yield: Fever and Tropical Infections
- Fever is a regulated rise in the hypothalamic set point driven by pyrogenic cytokines, distinct from hyperthermia.
- In tropical India the common infective causes of acute fever include malaria, dengue, typhoid, leptospirosis and scrub typhus.
- Falciparum malaria can cause cerebral malaria, severe anaemia, acute kidney injury and acute respiratory distress.
- The peripheral blood smear remains the gold standard for diagnosing and speciating malaria.
- Dengue warning signs include abdominal pain, persistent vomiting, mucosal bleeding and a rising haematocrit with falling platelets.
- Enteric fever classically presents with stepladder fever, relative bradycardia and later abdominal symptoms.
- An eschar is a valuable clue to scrub typhus, which responds rapidly to doxycycline.
- Sepsis is a dysregulated host response to infection with organ dysfunction, and needs early antibiotics and resuscitation.
- The elderly, neonates and immunocompromised may mount a blunted or absent fever response.
- Fever of unknown origin is prolonged fever above 38.3 degrees Celsius without a cause after appropriate initial evaluation.
- Rapid diagnostic tests aid malaria diagnosis where microscopy is unavailable but a negative test does not exclude it.
- A thick smear is more sensitive for detecting parasites while a thin smear allows species identification.
- Leptospirosis after freshwater or mud exposure can present with fever, conjunctival suffusion, myalgia and jaundice.
- Sputum acid-fast bacilli examination is essential when tuberculosis is a differential in prolonged fever.
- A structured travel, exposure and seasonal history sharpens the differential in tropical fever.
Approach to tropical fever
- **Common causes:** Malaria, dengue, typhoid, leptospirosis and scrub typhus in acute febrile illness across India.
- **Malaria:** Peripheral smear is the gold standard; thick film is sensitive, thin film for speciation.
- **Dengue red flags:** Abdominal pain, persistent vomiting, bleeding and a rising haematocrit with falling platelets.
- **Sepsis:** Organ dysfunction from a dysregulated response; needs early antibiotics and resuscitation.
NMC competencies in this chapter
- **IM4.1:** The febrile response and host determinants
- **IM4.3:** Common infectious causes of fever across India
- **IM4.6:** Pathophysiology and manifestations of malaria
- **IM4.7:** The sepsis syndrome
- **IM4.8:** Fever of unknown origin
- **IM4.12:** Diagnostic tests in the febrile patient
- **IM4.14:** Sputum acid-fast bacilli examination
- **IM4.15:** Interpretation of the malarial smear
Frequently Asked Questions
What is the gold-standard test for malaria?
The peripheral blood smear remains the gold standard; a thick film is more sensitive for detecting parasites and a thin film allows accurate species identification.
What are the warning signs in dengue?
Warning signs include severe abdominal pain, persistent vomiting, mucosal bleeding, lethargy and a rising haematocrit with a falling platelet count, which flag progression to severe dengue.
What defines fever of unknown origin?
It is fever above 38.3 degrees Celsius on several occasions lasting more than three weeks with no diagnosis after an appropriate initial evaluation.
How does this chapter help for NEET-PG?
Smear findings, dengue warning signs, the eschar of scrub typhus and sepsis definitions are recurring exam themes, so a structured febrile-illness approach maps directly to questions.
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