This document summarizes fever and febrile syndromes. It discusses the physiology of temperature regulation in the body and the pathogenesis of fever. It describes the different causes of fever including exogenous and endogenous pyrogens. It then discusses specific infectious causes of fever like malaria, enteric fever, dengue, leptospirosis, and scrub typhus. For each condition, it summarizes the causative organism, transmission, clinical features, diagnosis, and treatment. It also discusses complications, investigations, and management principles for febrile illnesses.

1. FEVER AND FEBRILE SYNDROMES
DR. AKSHAYA

2. PHYSIOLOGY OF TEMPERATURE
REGULATION
Warmth and
cold receptors
on skin
Preoptic anterior
hypothalamus
Posterior
hypothalamus
Temperature
of blood
bathing the
region

3. PHYSIOLOGY OF TEMPERATURE
REGULATION
Heat
production Heat
dissipation
HEAT PRODUCTION HEAT LOSS
Metabolic activity of liver Skin
Muscle activity Lungs

4. PHYSIOLOGY OF TEMPERATURE
REGULATION
• Normal daily variation in temperature – 0.5°C/1.0°F
• Diurnal variation: lowest at 6 am and maximum
between 4 and 6 pm
• Seasonal variation: low during summer
• Rectal > oral > axillary temperature
• Menstrual cycle: lower in the 2 weeks prior to
ovulation and rises during ovulation till menstruation

5. PATHOGENESIS OF FEVER
• Rise in hypothalamic set point.
• A temperature of >37.7°C (>99.9°F) defines a
fever.
• Rise in set point – heat conservation
(vasoconstriction) and heat production
(shivering and increased nonshivering
thermogenesis)
• Reset in set point – vasodilation and sweating

6. PATHOGENESIS OF FEVER
1. Crisis: Immediately temperature returns to
baseline eg. Pneumonia, sepsis, dengue
2. Lysis: temperature goes back slowly in step
ladder fashion over days eg. Uncomplicated
typhoid fever

7. PYROGENS
• Substances that cause fever
• Exogenous pyrogens: microbial products, toxins
and whole microorganisms eg. LPS of gram-
negative bacteria
• Pyrogenic cytokines: IL-1, IL-6, TNF, ciliary
neurotrophic factor, IFN-α

9. FEVER vs HYPERTHERMIA
• A fever of >41.5°C (106.7°F) is called hyperpyrexia.
• Hypothalamic fever – local trauma, hemorrhage,
tumor or intrinsic hypothalamic malfunction.
• Hyperthermia – setting of hypothalamic set point
is unchanged; does not respond to antipyretics.

11. MECHANISMS OF ANTIPYRETICS

12. ALARMING FEATURES
• PR >120/min
• SpO2 <92%
• Temp >41.5°C
• Altered sensorium/seizures/severe headache
• Cold extremities/hypotension
• Dyspnea/tachypnea/cyanosis
• Profuse diarrhea/severe abdominal
pain/dehydration/recurrent vomiting
• Decreased urine output
• Bleeding manifestations
• Muscle paralysis

13. TROPICODROMES

14. LOCALIZATION
• ENT: tonsils/sinusitis/ear discharge/mastoid
tenderness
• Cardiovascular: new/changing murmur; signs of IE
• Liver: Tender hepatomegaly/ murphy’s sign
• Dental: periodontal swelling/ abscess
• Genitourinary: suprapubic tenderness/ renal
angle/cervical motion tenderness

15. LOCALIZATION
• Musculoskeletal: joint swelling/tenderness, bone
swelling/tenderness
• Skin: redness/
swelling/tenderness/bullae/crepitus
• Lymphadenopathy
• Abdomen: lump, guarding,tenderness
• Respiratory: crepitation/ effusion

16. INVESTIGATIONS
Hemogram
RDTs/thick smear
Dengue-NS1
Dengue/scrub/Leptospira IgM ELISA
Blood and urine cultures
Throat swab for influenza
CXR
USG abdomen

17. MALARIA
• Caused by protozoa of the genus Plasmodium –
P. vivax, P. falciparum, P. malariae, P. ovale, P.
knowlesi.
• Transmitted by the bite of female Anopheles
mosquito – after 10-14 days.
• Life cycle: Pre-erythrocytic schizogony and
erythrocytic schizogyny.

18. CLINICAL FEATURES
• Fever is the cardinal symptom of malaria. Often
accompanied by
 Headache
 Myalgia
 Arthralgia
 Anorexia
 Nausea and vomiting
• Physical findings – mild anemia, mild jaundice and
splenomegaly.

21. DIAGNOSIS
• Microscopy: Thick film increase sensitivity and
thin film helps in species identification.
• Rapid Diagnostic test: simple, sensitive and
specific. RDTs target HRP2 and pLDH.
Pf HRP-2 based kits may show positive result upto
3 weeks after successful treatment and parasite
clearance.

22. TREATMENT OF VIVAX MALARIA

23. TREATMENT OF FALCIPARUM MALARIA

24. TREATMENT OF COMPLICATED MALARIA
• Open iv line for 8 hours of IVF including diluents for
antimalarial medicine
• Exclude or treat hypoglycemia
• Blood transfusion
• Tepid sponging
• Consider other infections and need for anti-
convulsant treatment

26. ENTERIC FEVER
• Systemic disease characterized by fever and
abdominal pain and caused by dissemination of
S. typhi or S. paratyphi
• No known hosts other than humans.
• Most commonly, food-borne or waterborne
transmission results from fecal contamination by
ill or asymptomatic chronic carriers

27. ENTERIC FEVER
• Incubation period is about 5-21 days.
• First week: “stepwise” fever and relative
bradycardia
• Second week: abdominal pain and rose spots
• Third week: Hepatosplenomegaly, intestinal
perforation or bleeding leading to peritonitis

28. ENTERIC FEVER
• Definitive diagnosis: isolation of S. typhi or S.
paratyphi from blood, bone marrow or other
sterile sites such as rose spots, stool or intestinal
secretions
• Serological tests include Widal and Typhidot IgM
Widal agglutination test is considered to be positive
if a four-fold or greater increase in titer in paired
samples of acute and convalescent sera is
documented

29. ENTERIC FEVER
• Ceftriaxone and high-dose azithromycin remain
the main drugs for the treatment of enteric fever
• Chronic carriers – oral amoxicillin, ciprofloxacin,
norfloxacin or TMP-SMX for 4-6 weeks
• Vaccines – Ty21a on days 1,3,5 and 7 with a
booster every 5 years; Vi polysaccharide
parenteral vaccine given in a single dose with a
booster every 2 years

30. DENGUE
• A major public health concern.
• Upsurge in cases during the period July –
November in India.
• Transmitted by Aedes aegypti and Aedes
albopictus.
• IP – 5 to 7 days

32. COURSE OF DENGUE ILLNESS
• FEBRILE PHASE
• CRITICAL PHASE
• RECOVERY PHASE

33. DENGUE FEVER
AFI of 2-7 days duration with ≥2 of the following
manifestations:
 Headache
 Retro-orbital pain
 Myalgia
 Arthralgia
 Rash
 Haemorrhagic manifestations

34. FEBRILE PHASE
• Lasts for 2-7 days
• Positive tourniquet test
• Earliest change is progressive decrease in TLC
• Higher plasma ALT and AST

35. CRITICAL PHASE
• D3-D7 of fever

36. RECOVERY PHASE
• 48 to 72 hrs following critical phase
• General well-being improves
• Appetite returns
• GI symptoms abate
• Hemodynamic status stabilizes
• Diuresis ensues

38. SEVERE DENGUE

41. MAINTENANCE FLUIDS

42. CRITERIA FOR DISCHARGE
 Afebrile for atleast 24 hrs
 No respiratory distress
 Adequate urine output
 Minimum of 2-3 days after recovery from
shock
 Return of appetite
 Platelet count >50,000/mm³

43. LEPTOSPIROSIS
• Global public health problem.
• Peak incidence in summer and epidemics
following unusually heavy rainfall and
monsoons.
• Humans get infected through indirect contact
with water or soil contaminated by the urine of
infected animals.

44. LEPTOSPIROSIS
o IP – 2 to 26 days
o Mild leptospirosis:
 Flu-like illness with fever, nausea, vomiting,
abdominal pain, conjunctival suffusion
 Severe headache and myalgia
 Spontaneous resolution in 7 – 10 days

45. LEPTOSPIROSIS
o Severe Leptospirosis:
 Renal insufficiency
 Hepatic dysfunction
 Hemorrhage
 Myocarditis
 High mortality
Triad of hemorrhage, jaundice and AKI – “Weil’s
syndrome”

46. LEPTOSPIROSIS
• Diagnosis: Direct detection of organisms or
serology
• Assays include MAT, IHA and ELISA
• Definitive diagnosis – isolation of the organism,
positive result in the PCR, seroconversion, rise
in antibody titer (four-fold or greater rise)

47. LEPTOSPIROSIS
• Severe cases – iv penicillin or Ceftriaxone or
Doxycycline
• Mild cases – oral doxycycline, azithromycin,
ampicillin or amoxicillin
• Preventive measures:
 Avoidance of exposure to urine and tissues from
infected animals through protective equipment
 Rodent control strategies

48. SCRUB TYPHUS
• Causative organism, Orientia tsutsugamushi,
obligate intracellular gram-negative bacterium
• India: kato, karp serotypes
• Transmitted to humans by trombiculid mites –
chiggers (Leptotrombidium)
• Most cases occur between August and February

49. SCRUB TYPHUS
• IP is 5 -20 days
• Fever, myalgia, headache, generalized
lymphadenopathy, GI symptoms, cough, transient
hearing loss, eschar and rash
• Eschar – neck, axillae, chest, abdomen, groin
• Associated complications – ARDS, interstitial
pneumonitis, meningoencephalitis, ARF, shock, GI
bleeding and coagulopathy

50. SCRUB TYPHUS
• Thrombocytopenia, leukopenia or leukocytosis,
elevations in hepatic enzymes, bilirubin and
creatinine
• Weil-Felix test: lacks sensitivity and specificity
• IgM ELISA against a recombinant 56 kDa protein
– reliable method for early detection of scrub
typhus

51. SCRUB TYPHUS
• DOC – Doxycycline
• Alternatives – Azithromycin, rifampicin,
chloramphenicol

52. THANK YOU