Major Infectious Diseases of Humans

• Pathogens cause two general categories of diseases: Microbial intoxications and Infectious diseases
• Infectious diseases


  Diseases caused by pathogens following colonization of some body site by the pathogen
• Some infectious diseases affect more than one anatomical site, and some pathogens move from one body site to another during the course of a disease
• Skin infectious diseases


  • Dermatitis
  • Folliculitis
  • Sty (or stye)
  • Furuncle
  • Carbuncle
  • Macule
  • Papule
  • Pustule
  • Vesicle

  
• Skin


  • Epidermis and dermis
  • Sebaceous glands

  
• There are three pathways for pathogens to enter the ear: Via the eustachian (auditory) tube, from the throat and nasopharynx; Via the external ear canal; Via the blood or lymph
• Otitis media


  Infection of the middle ear
• Otitis externa


  Infection of the outer ear canal
• Eye


  • Conjunctiva, conjunctivitis, keratitis, keratoconjunctivitis, retinitis
• Parts of the respiratory system


  • Upper respiratory tract (URT): paranasal sinuses, nasopharynx, oropharynx, epiglottis, and larynx
  • Lower respiratory tract (LRT): trachea, bronchial tubes, and alveoli of the lungs
• Indigenous microbiota of the URT may cause opportunistic infections of the respiratory system
• LRT infections are the most common cause of death from infectious diseases
• Respiratory system infectious diseases

  • Bronchitis
  • Bronchopneumonia
  • Epiglottitis
  • Laryngitis
  • Pharyngitis
  • Pneumonia
  • Sinusitis
• The oral cavity is a complex ecosystem, suitable for growth of many types of microbes
• Oral infectious diseases


  • Dental caries
  • Periodontal diseases
  • Gingivitis
  • Periodontitis
  • Trench mouth
• Transient and resident microbes continuously enter and leave the GI tract, and most microbes are destroyed in the stomach and duodenum
• GI tract infectious diseases

  • Colitis
  • Diarrhea
  • Dysentery
  • Enteritis
  • Gastritis
  • Gastroenteritis
  • Hepatitis
• Diarrhea can have many causes (e.g., foods, drugs, viruses, bacteria, protozoa, or helminths)
• Urinary tract infectious diseases

  • Cystitis
  • Nephritis
  • Ureteritis
  • Urethritis
  • Prostatitis
  • Pyelonephritis
• The most common cause of cystitis and pyelonephritis is E. coli; the most common cause of urethritis is Chlamydia trachomatis
• Genital tract infectious diseases

  • Bartholinitis
  • Cervicitis
  • Endometritis
  • Epididymitis
  • Pelvic inflammatory disease (PID)
  • Vaginitis
  • Vulvovaginitis
• Sexually transmitted diseases (STDs) include any of the infections transmitted by sexual activities, and sometimes include diseases of not only the genital and urinary tracts, but other areas of the body as well (e.g., skin, mucous membranes)
• Cardiovascular infectious diseases


  • Endocarditis
  • Myocarditis
  • Pericarditis
• Blood is normally sterile
• Lymphatic system infectious diseases

  • Lymphadenitis
  • Lymphadenopathy
  • Lymphangitis
• Central nervous system infectious diseases

  • Encephalitis
  • Encephalomyelitis
  • Meningitis
  • Meningoencephalitis
  • Myelitis
• There is no indigenous microbiota of the nervous system
• Causes of meningitis


  • Ingestion of poisons
  • Ingestion or injection of drugs
  • Reaction to a vaccine
  • Pathogen (virus, bacterium, fungus, or protozoan)
• Major causes of bacterial meningitis

  • Haemophilus influenzae
  • Neisseria meningitidis
  • Streptococcus pneumoniae
• Because of vaccination, these organisms are not commonly encountered in the CML's of the developed world
• Common opportunistic infections


  • Aspergillosis and other mould infections
  • Candidiasis
  • Cytomegalovirus (CMV) and herpes simplex infections
  • Tuberculosis, toxoplasmosis
  • Mycobacterium avium and Pneumocystis infections
• Examples of emerging infections

  • Avian influenza (bird flu)
  • Chaga's Disease
  • Chikungunya virus
  • Hemolytic uremic syndrome and other E. coli O157 infections
  • Ebola hemorrhagic fever
  • Hantavirus pulmonary syndrome (HPS)
  • HIV infection and Aids
  • Human monkeypox
  • Lassa fever
  • Legionellosis
  • Lyme disease
  • Marburg hemorrhagic fever
  • Middle East respiratory syndrome (MERS-CoV)
  • Zika virus
• Examples of reemerging infections

  • Cholera
  • Dengue fever
  • Diphtheria
  • Malaria
  • Mumps
  • Rift Valley fever
  • Tuberculosis
  • Yellow fever
  • Infections caused by MRSA and other "superbugs"