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Questions and Answers
Which bacterial infection is commonly associated with chronic infection of the lung?
Which bacterial infection is commonly associated with chronic infection of the lung?
Which laboratory test is particularly indicated for suspected cases of tuberculosis?
Which laboratory test is particularly indicated for suspected cases of tuberculosis?
What type of malignancy is categorized as hematologic?
What type of malignancy is categorized as hematologic?
Which therapeutic agent is specifically used for the treatment of amoeba infections?
Which therapeutic agent is specifically used for the treatment of amoeba infections?
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What imaging study is appropriate for evaluating potential lung infections?
What imaging study is appropriate for evaluating potential lung infections?
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What is the main causative organism of brucellosis?
What is the main causative organism of brucellosis?
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Which of the following is a common mode of infection for HIV?
Which of the following is a common mode of infection for HIV?
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What clinical symptom is indicative of brucellosis?
What clinical symptom is indicative of brucellosis?
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Which diagnostic test is best for confirming HIV infection?
Which diagnostic test is best for confirming HIV infection?
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Which treatment is commonly prescribed for brucellosis?
Which treatment is commonly prescribed for brucellosis?
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What is a significant complication associated with AIDS?
What is a significant complication associated with AIDS?
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A patient with brucellosis may present with which of the following symptoms?
A patient with brucellosis may present with which of the following symptoms?
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What defines a fever of unknown origin (FUO)?
What defines a fever of unknown origin (FUO)?
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Which of the following correctly describes the causative organism of typhoid fever?
Which of the following correctly describes the causative organism of typhoid fever?
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What is the mode of transmission for typhoid fever?
What is the mode of transmission for typhoid fever?
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In which week of typhoid fever is the Widal test expected to be positive?
In which week of typhoid fever is the Widal test expected to be positive?
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What clinical manifestation is associated with the 1st week of typhoid fever?
What clinical manifestation is associated with the 1st week of typhoid fever?
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Which type of fever is characterized by daily fluctuations of less than 1ºC?
Which type of fever is characterized by daily fluctuations of less than 1ºC?
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Which of the following regarding the complications of typhoid fever is correct?
Which of the following regarding the complications of typhoid fever is correct?
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What is indicated by a culture being positive in the first week of typhoid fever?
What is indicated by a culture being positive in the first week of typhoid fever?
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How is hyperpyrexia defined in terms of body temperature?
How is hyperpyrexia defined in terms of body temperature?
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Study Notes
Infectious Diseases
- Infectious diseases are a broad category encompassing various illnesses caused by pathogens.
- Important infectious diseases include typhoid fever, brucellosis, and acquired immunodeficiency syndrome (AIDS).
- Normal body temperature ranges from 36.5°C to 37.2°C.
- Fever is defined as having a body temperature above the normal upper limit.
- Hyperpyrexia is a fever exceeding 40°C.
- Types of fever include sustained, remittent, hectic, and relapsing fever.
Aetiological Classification
-
Bacterial:
- Gram-positive: streptococci, staphylococci
- Gram-negative: Klebsiella, Pseudomonas, Haemophilus influenza
- Anaerobic bacteria: bacteroides
- Mycobacterial: Tuberculosis (TB), Leprosy
- Spirochetal: Syphilis, Leptospirosis
- Rickettsia: Typhus
- Chlamydia
- Viral: Dengue, Influenza, Herpes simplex virus (HSV), Varicella-zoster virus (VZV), Cytomegalovirus (CMV), Epstein-Barr virus (EBV), Measles, Mumps, Rubella
- Protozoal: Malaria, Amebiasis, Bilharziasis, Giardiasis
- Fungal: Candida albicans, Aspergillus niger
Typhoid Fever
- Etiology: Salmonella typhi and paratyphi A and B
- Mode of Infection: Feco-oral transmission
-
Clinical Manifestations:
- First week: Fever (stepladder pattern), headache, relative bradycardia, constipation, rose spots
- Second week: Continuous fever, tachycardia, diarrhea, splenomegaly
- Third week: convalescence begins
- Complications: Intestinal bleeding, peritonitis, meningitis, encephalitis, convulsions, pyelonephritis
- Investigations: CBC (leucopenia with relative lymphocytosis), Widal test (positive from the second week – prognostic rather than diagnostic), cultures (blood, stool, urine, in weeks 1-3 respectively).
- Treatment: Ciprofloxacin, Co-trimoxazole, ceftriaxone
Brucellosis
- Etiology: Brucella (melitensis, abortus, or suis)
- Mode of Infection: Contaminated milk, or remnants from aborted animals.
- Clinical Picture: Bone and muscle pain, vomiting, constipation, relapsing fever. Fever for 10 days followed by 10 days of apyrexia- cycling fever. Hepatosplenomegaly and lymph node enlargement.
- Complications: Relapse, infective endocarditis, orchitis, paraplegia (transverse myelitis), abortion.
- Investigations: CBC (lymphocytosis positive during fever spike), Blood culture, Serological tests (Brucella agglutination test - the best diagnostic test).
- Treatment: Doxycycline or rifampicin for 6 weeks.
Acquired Immunodeficiency Syndrome (AIDS)
- Etiology: Human Immunodeficiency Virus (HIV)
- Modes of Infection: Parenteral, sexual, vertical
- Pathogenesis: HIV infects T-lymphocytes, suppressing cellular and humoral immunity. A fall below 200 T-cells/dL leads to opportunistic illnesses and malignancies.
- Clinical Picture: Asymptomatic phase (up to 10 years), acute HIV syndrome (fever, rigors, arthralgia, rash), symptomatic syndromes (generalized LN enlargement, Constitutional symptoms, Neurological disease, Opportunistic infections, Secondary neoplasms).
- Investigations: HIV antibodies (screening, appear within 2 weeks of infection), HIV-RNA by PCR (best diagnostic test).
- Treatment: Anti-retroviral (HAART), Zidovudine 600 mg/day orally (note that HAART involves multiple drugs in practice).
Fever of Unknown Origin (FUO)
- Definition: Persistent elevation of body temperature above 38.5°C for 3 weeks without a diagnosed cause. Requires 1 week of inpatient investigations.
- Causes: Bacterial (TB, infective endocarditis, typhoid fever, brucellosis, lung abscess, pyelonephritis), Viral (EBV, CMV, HIV, hepatitis), Protozoal (malaria, amebiasis), Malignancy (hematologic and non-hematologic), Collagen diseases (rheumatic fever, PAN, SLE), Others (inflammatory bowel disease, hemolysis, cerebral hemorrhage).
- Undiagnosed Often the cause is unidentified even after comprehensive investigation.
Other Topics/Notes
- Preventive measures (hand hygiene, respiratory precautions)
- Investigations (laboratory, imaging, endoscopy, biopsies, etc.)
- Treatment regimens (for TB, malaria, etc.). Details on the use of different medicines are not included in this summary for safety and efficacy reasons.
Pulmonary Tuberculosis (TB)
- Definition: Chronic lung infection caused by Mycobacterium tuberculosis.
- Etiology: Mycobacterium tuberculosis (acid-fast, intracellular, aerobic, non-motile bacillus)
- Risk Factors: Children under 5, close contacts with active TB patients, immunocompromised individuals (AIDS, diabetes, leukemia, steroid users)
- Mode of Transmission: Droplet infection.
- Clinical Picture: Symptoms (night fever, sweating, weight loss, appetite loss), cough and expectoration (thick mucoid), hemoptysis (blood-tinged sputum), sings (inspection, percussion, auscultation), complicated TB with massive systemic spread in immunocompromised patients, tubercles in CNS, lungs, pericarditis, Pott's disease of spine, generalized lymphoma.
- Investigations: Chest X-ray, ESR and CRP (elevated), sputum examination (acid-fast bacilli staining), PCR (Mycobacterial DNA detection), Seriological tests (Quantiferon Gold, ADA), Tuberculin skin testing.
- Treatment: First-line drugs (isoniazid, rifampicin, pyrazinamide, ethambutol, and streptomycin), combination therapy for long periods, standardized 6-month regimen. Indications for corticosteroids vary.
Dengue Fever
- Definition: Viral disease caused by the dengue virus.
- Etiology: Dengue virus (RNA virus, Flavivirus, arbovirus).
- Vector: Aedes aegypti mosquito.
- Pathogenesis: Virus inoculated by the bite of an infected mosquito, replicates in the reticuloendothelial system. Secondary infections may cause antibody response and complications.
- Clinical Features: Incubation (5-9 days), social history (residence in or travel to endemic region). Initial fever (2-4 days), rapid defervescence, afebrile period (1 day), second fever period (2-3 days). Generalised lymphadenopathy, skin rash (itchy maculopapular), GIT issues, CNS and CVS symptoms,
- Complications: Dengue shock syndrome (DSS), Dengue haemorrhagic fever (DHF).
- Investigations: Haematology (Elevated Hct, leucopenia, low platelets), Biochemistry (Elevated liver enzymes), Immunology (Dengue Antibody - IgM and IgG ELISA), Microrbiology (PCR possible).
- Management: Support (intravenous fluids, colloids, paracetamol). Possible platelet transfusion.
- Prevention: Vector control, biological agents
- Prognosis: Mortality 10-30% in dengue haemorrhagic fever.
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Description
Explore the fundamentals of infectious diseases, including their types, causes, and categorization by pathogens. This quiz covers bacterial, viral, and protozoan diseases, alongside key concepts like fever classifications. Test your knowledge on crucial infectious diseases such as AIDS and tuberculosis.
