Diseases & Clinical Algorithms

Chronic, slowly progressive bacterial infection by Actinomyces spp. causing cervicofacial, thoracic, or abdominal mass/fistula.

Delayed autoimmune complication of group A streptococcal pharyngitis, causing carditis, arthritis, chorea, erythema marginatum.

DNA virus causing pharyngoconjunctival fever, severe pneumonia, and epidemic keratoconjunctivitis.

Respiratory infection by adenoviruses; can cause severe pneumonia, ARDS, and bronchiolitis obliterans.

Parasitic infection of the large intestine caused by Entamoeba histolytica; may cause dysentery or extra‑intestinal abscess.

Zoonotic Bacillus anthracis infection; cutaneous (most common), inhalational, or gastrointestinal; bioterrorism agent.

Soil‑transmitted helminthiasis of the small intestine caused by Ascaris lumbricoides; often asymptomatic, can cause obstruction.

Zoonotic infection by Brucella spp. via unpasteurized dairy or animal contact, causing undulant fever and arthritis.

Acute enteritis caused by Campylobacter spp., mainly C. jejuni, typically from poultry.

Flea‑transmitted Bartonella henselae infection from cats; regional lymphadenitis, fever; rarely hepatosplenic or neuroretinitis.

Trypanosoma cruzi infection via triatomine bugs, causing acute phase then chronic cardiomyopathy/megasyndromes decades later.

Mosquito‑borne alphavirus causing acute fever and severe arthralgia; can persist months.

Acute, secretory diarrhoeal disease caused by toxigenic Vibrio cholerae O1 or O139.

Soil‑dwelling dimorphic fungus causing acute pneumonia or disseminated disease; endemic in arid Americas.

Acute respiratory disease caused by SARS‑CoV‑2; spectrum from asymptomatic to severe pneumonia, ARDS, multi‑organ failure.

Rapidly progressive, fatal neurodegenerative prion disease; sporadic (85%), genetic (10–15%), variant (vCJD) linked to BSE.

Encapsulated yeast infection, primarily causing subacute meningitis in HIV/AIDS; also pneumonia and skin lesions.

Intestinal coccidian parasite causing watery diarrhoea; severe in immunocompromised, especially HIV/AIDS.

Intestinal coccidian infection causing prolonged watery diarrhoea, often foodborne; caused by Cyclospora cayetanensis.

Larval T. solium infection of tissues, mainly brain (neurocysticercosis – NCC); leading cause of adult‑onset epilepsy in endemic regions.

Flavivirus infection transmitted by Aedes mosquitoes; spectrum from mild fever to severe haemorrhagic shock.

Toxin‑mediated bacterial infection causing pharyngeal pseudomembrane, myocarditis, and neuropathy.

Filovirus causing severe haemorrhagic fever with high mortality, transmitted via body fluids.

Common childhood pinworm infection (Enterobius vermicularis) causing perianal itching, transmitted via faecal‑oral route.

Diarrhoeal disease caused by EPEC strains, often in infants, with attaching‑effacing lesions.

Acute watery diarrhoea due to ETEC heat‑labile/stable enterotoxins; most common cause of travellers’ diarrhoea.

Non‑polio enterovirus causing severe respiratory illness, especially in children with asthma; associated with acute flaccid myelitis.

Non‑polio enterovirus causing respiratory illness; rarely asymmetric limb weakness/acute flaccid myelitis (AFM).

Most common bacterial STI; Chlamydia trachomatis causes urethritis, cervicitis, PID, tubal infertility, and ectopic pregnancy.

Small‑intestinal protozoal infection causing diarrhoea, malabsorption, and bloating, caused by Giardia lamblia.

Rare zoonotic Burkholderia mallei infection from horses, causing cutaneous/nasal/pulmonary infection; potential bioterrorism agent.

Sexually transmitted Neisseria gonorrhoeae causing urethritis, cervicitis, PID, epididymitis; increasing antimicrobial resistance.

Invasive bacterial infection causing epiglottitis, meningitis, pneumonia in unimmunized children.

Old‑World hantaviruses causing acute renal failure, thrombocytopenia, and haemorrhage.

Acute viral zoonosis from Old World hantaviruses; fever, acute kidney injury, haemorrhage, shock.

Acute febrile illness with vesicular lesions on hands, feet, and oral mucosa, caused by Coxsackievirus A16 or Enterovirus 71.

Rodent‑borne hantavirus causing prodrome then rapidly progressive pulmonary oedema and cardiogenic shock.

Acute, self‑limited viral hepatitis transmitted faeco‑orally, often associated with contaminated food/water.

Parenterally and sexually transmitted DNA virus causing acute hepatitis; high chronicity risk in neonates.

Blood‑borne flavivirus causing slowly progressive hepatitis, cirrhosis, and hepatocellular carcinoma.

Defective RNA virus requiring HBV for replication; co‑infection or superinfection of HBV, causing severe liver disease.

Sexually transmitted ulcerative infection by HSV‑2 (or HSV‑1); chronic with recurrent painful ulcers.

Recurrent vesicular lesions of the lips/oral mucosa due to HSV‑1 latency and reactivation.

Reactivation of latent VZV in dorsal root ganglia causing painful dermatomal vesicular rash.

Dimorphic fungus (Histoplasma capsulatum) causing pulmonary or disseminated infection; endemic in Americas, Africa, Asia.

Retroviral infection causing progressive CD4+ T‑cell depletion, leading to opportunistic infections and malignancies.

Small‑intestinal blood‑feeding nematodes (Ancylostoma duodenale, Necator americanus) causing iron‑deficiency anaemia and hypoalbuminaemia.

Acute respiratory infection resembling RSV, causing bronchiolitis, pneumonia, and exacerbations of COPD/asthma.

Acute viral respiratory infection characterised by sudden fever, myalgia, cough; annual epidemics and occasional pandemics.

Severe filamentous fungal infection of lungs/sinuses in neutropenic, transplant, and critically ill patients.

Bloodstream or deep‑tissue infection by Candida spp., typically in ICU, immunocompromised, abdominal surgery patients.

Severe infection by Streptococcus pneumoniae causing bacteraemia, meningitis, and pneumonia.

Mosquito‑borne flavivirus causing acute encephalitis; leading cause of viral encephalitis in Asia.

Tick‑borne rickettsial infection (Rickettsia japonica) causing fever, eschar, and maculopapular rash.

Arenavirus causing acute haemorrhagic fever, often mild or subclinical; endemic in West Africa.

Persistent immune‑controlled Mycobacterium tuberculosis without active disease; reactivation risk 5–10% lifetime.

Protozoan infection transmitted by sandflies; visceral form causes fever, hepatosplenomegaly; cutaneous causes chronic skin ulcers.

Chronic granulomatous infection by Mycobacterium leprae affecting skin, peripheral nerves, and upper respiratory tract.

Zoonotic spirochetal infection from animal urine, causing febrile illness to multi‑organ failure with jaundice and renal impairment.

Tick‑borne spirochetal infection (Borrelia burgdorferi sensu lato) causing skin, joint, cardiac, and neurological manifestations.

Mosquito‑borne protozoan infection; P. falciparum causes severe anaemia, cerebral malaria, and multi‑organ failure.

Filovirus closely related to Ebola, causing sporadic severe outbreaks of haemorrhagic fever.

Highly contagious airborne paramyxovirus causing fever, cough, coryza, conjunctivitis, and maculopapular rash.

Environmental saprophyte infection (Burkholderia pseudomallei) in tropics; causes pneumonia, abscesses, sepsis; high mortality.

Invasive Neisseria meningitidis infection causing meningitis and/or fulminant sepsis.

Opportunistic infection by obligate intracellular fungi, causing diarrhoea, keratoconjunctivitis, or disseminated disease.

Zoonotic poxvirus causing febrile rash illness with lymphadenopathy; can be severe in immunocompromised.

Aggressive angio‑invasive mould infection; rhino‑orbital‑cerebral, pulmonary, or cutaneous; high mortality.

Paramyxovirus infection causing painful parotid swelling, orchitis, pancreatitis, and meningoencephalitis.

Flea‑borne rickettsial infection (Rickettsia typhi) causing fever, headache, and rash.

Chronic, progressively destructive subcutaneous infection by fungi or actinomycetes; painless mass, sinus tracts, grains.

Actinomycete infection (Nocardia spp.) causing pulmonary infiltrates/cavities, brain abscess, or disseminated disease.

Highly contagious viral gastroenteritis causing outbreaks of vomiting and diarrhoea in closed settings.

Filarial infection transmitted by blackflies, causing pruritus, skin atrophy, and blindness due to corneal microfilariae.

Arboviral disease transmitted by Culicoides midges causing acute fever, headache, myalgia; second most frequent arbovirus in Amazon.

Common respiratory virus causing croup, bronchiolitis, and pneumonia, especially in young children; serotypes 1–4.

Clinically similar to typhoid but caused by S. Paratyphi A, B, or C; generally milder.

Highly contagious respiratory disease caused by Bordetella pertussis, characterised by paroxysmal cough and post‑tussive vomiting.

Zoonotic flea‑borne Yersinia pestis infection; bubonic (lymphadenitis), septicaemic, or pneumonic forms.

Fungal pneumonia causing severe hypoxic respiratory failure in immunocompromised patients (HIV, transplant, chemotherapy).

Enterovirus (poliovirus types 1, 2, 3) causing acute flaccid paralysis; wild‑type 2 and 3 eradicated.

Zoonotic intracellular bacterium Coxiella burnetii causing acute febrile illness, atypical pneumonia, or chronic endocarditis.

Fatal encephalomyelitis caused by Lyssavirus transmitted via infected animal bite.

Major cause of bronchiolitis and pneumonia in infants, with recurrent wheeze sequelae.

Acute dehydrating diarrhoea caused by rotavirus; leading cause of severe infantile diarrhoea worldwide.

Mild viral exanthem; congenital rubella syndrome (CRS) causes deafness, cataracts, heart defects if infection in first trimester.

Trematode infection (Schistosoma spp.) causing intestinal/hepatic (S. mansoni, japonicum) or urogenital (S. haematobium) disease.

Mite‑borne rickettsial infection (Orientia tsutsugamushi) causing fever, eschar, lymphadenopathy.

Acute invasive enteric infection caused by Shigella spp., leading to bloody diarrhoea (dysentery).

Exotoxin‑mediated severe illness with fever, rash, hypotension, and multiorgan failure.

Threadworm infection caused by Strongyloides stercoralis that can autoinfect, persist decades, and cause hyperinfection in immunosuppression.

Chronic spirochetal STI with primary chancre, secondary rash, latent period, and late destructive tertiary disease.

Intestinal infection with adult tapeworms (Taenia saginata or T. solium) from undercooked beef or pork, often asymptomatic.

Toxin‑mediated spastic paralysis from Clostridium tetani spores entering wounds; neonatal tetanus via umbilical stump.

Flavivirus transmitted by tick bite or unpasteurized milk; causes meningitis/meningoencephalitis.

Protozoan infection from undercooked meat/cat faeces; causes lymphadenopathy, retinochoroiditis; severe congenital disease.

Chronic conjunctivitis by Chlamydia trachomatis serovars A–C; leading infectious cause of blindness.

Colonic infection causing colitis, dysentery, and rectal prolapse in heavy infections; caused by Trichuris trichiura (whipworm).

Airborne mycobacterial infection primarily of the lungs, causing cough, fever, night sweats, and weight loss.

Highly infectious zoonotic bacterium Francisella tularensis; ulceroglandular, oculoglandular, pneumonic, or typhoidal forms.

Systemic infection caused by Salmonella enterica serovar Typhi, transmitted faeco‑orally.

Highly contagious primary VZV infection causing pruritic vesicular rash; reactivates as herpes zoster.

Mosquito‑borne flavivirus causing febrile illness, rarely meningitis/encephalitis; maintained in bird‑mosquito cycle.

Mosquito‑borne flavivirus causing haemorrhagic fever with jaundice; severe cases have 20–50% mortality.

Mosquito‑borne and sexually transmitted flavivirus causing mild fever, rash; congenital infection causes microcephaly.