1.2

• Diarrhea can have many causes. It may or may not be the result of an infectious disease. When diarrhea is the result of an infectious disease, the pathogen may be a virus, a bacterium, a protozoan, or a helminth.
• Dysentery (a severe form of diarrhea) may also be caused by various pathogens, including bacteria (e.g., Shigella spp. cause bacillary dysentery) and protozoa (e.g., those that cause amebiasis and balantidiasis).
• Viral gastroenteritis


  Also known as viral enteritis and viral diarrhea
• Viral gastroenteritis


  • It may be an endemic or epidemic illness in infants, children, and adults
  • Symptoms include nausea, vomiting, diarrhea, abdominal pain, myalgia
  • Often a self-limiting disease lasting 24 to 48 hours
  • Can be fatal in an infant or young child, especially when caused by a rotavirus
  • Responsible for more than 800,000 diarrheal deaths per year in developing countries
  • Not a nationally notifiable disease in the United States
  • Norovirus is the leading cause of illness and outbreaks from contaminated food in the United States
• Patient care


  • Use Standard Precautions for hospitalized patients
  • Add Contact Precautions for diapered or incontinent patients and for patients with norovirus and rotavirus infections
• Pathogens causing viral gastroenteritis in children

  • Enteric adenoviruses
  • Astroviruses
  • Caliciviruses (including noroviruses)
  • Rotaviruses
• Pathogens causing viral gastroenteritis in children and adults

  • Norovirus-like viruses
  • Rotaviruses
• Reservoirs


  • Infected humans
  • Contaminated water and shellfish
• Transmission


  • Fecal-oral route
  • Airborne transmission
  • Contact with contaminated fomites
  • Foodborne, waterborne, and shellfish transmission
• Laboratory diagnosis


  • Molecular-based assays
  • Electron microscopic examination of stool specimens
  • Immunodiagnostic procedures
• Hepatitis


  Inflammation of the liver, can have many causes including alcohol, drugs, and viruses
• Viruses that can cause viral hepatitis

  • Hepatitis A virus (HAV)
  • Hepatitis B virus (HBV)
  • Hepatitis C virus (HCV)
  • Hepatitis D virus (HDV)
  • Hepatitis E virus (HEV)
• Viral hepatitis


  Hepatitis caused by any one of about a dozen different viruses
• Patient care


  • Use Standard Precautions for hospitalized patients
  • Add Contact Precautions for diapered or incontinent patients
• Laboratory diagnosis


  Various immunodiagnostic procedures and molecular assays are available
• The World Health Organization estimates that approximately 240 million people are chronically infected with HBV worldwide, that about 600,000 people die each year as a result of HBV infections, and that more than 2 million new acute clinical cases occur annually.
• HAV vaccine


  Contains inactivated virus grown in cell culture, recommended for people at increased risk of acquiring hepatitis A
• HBV vaccine


  A subunit vaccine, produced by genetically engineered Saccharomyces cerevisiae (common baker's yeast), now routinely administered to U.S. children
• Genital herpes


  Characterized by a localized primary lesion, latency, and a tendency to localized recurrence
• Genital herpes


  • In women, the principal sites of primary infection are the cervix and vulva, with recurrent disease affecting the vulva, perineal skin, legs, and buttocks
  • In men, lesions appear on the penis, and in the anus and rectum of those engaging in anal sex
  • Initial symptoms are usually itching, tingling, and soreness, followed by a small patch of redness and then a group of small, painful blisters
  • The blisters break and fuse to form painful, circular sores, which become crusted after a few days
  • The sores heal in about 10 days but may leave scars
  • The initial outbreak is more painful, prolonged, and widespread than subsequent outbreaks and may be associated with fever
• Patient care


  • Use Standard Precautions for hospitalized patients
  • Add Contact Precautions for severe disseminated or primary mucocutaneous herpes
• Genital warts


  • Start as tiny, soft, moist, pink or red swellings, which grow rapidly and may develop stalks
  • Their rough surfaces give them the appearance of small cauliflowers
  • Multiple warts often grow in the same area, most often on the penis in men and the vulva, vaginal wall, cervix, and skin surrounding the vaginal area in women
  • Also develop around the anus and in the rectum in men or women who engage in anal sex
  • Can become malignant
• Pathogens causing genital herpes

  Usually HSV-2, but occasionally HSV-1
• Reservoirs and mode of transmission for genital herpes

  • Infected humans serve as reservoirs
  • Transmission occurs via direct sexual contact or oral-genital, oral-anal, or anal-genital contact during the presence of lesions
  • Mother-to-fetus or mother-to-neonate transmission occurs during pregnancy and birth
• Laboratory diagnosis of genital herpes


  Diagnosed by observation of characteristic cytologic changes in tissue scrapings or biopsy specimens, and the presence of multinucleated giant cells with intranuclear inclusions, and confirmation by immunodiagnostic, molecular diagnostic procedures and cell culture
• Pathogens causing genital warts

  • 30-40 types of HPV in the Papovaviridae family of DNA viruses (human wart viruses)
  • HPV genotypes 16 and 18 have been strongly associated with cervical cancer
• Reservoirs and mode of transmission for genital warts

  • Infected humans serve as reservoirs
  • Transmission occurs via direct contact, usually sexual; through breaks in skin or mucous membranes; or from mother to neonate during birth
• Laboratory diagnosis of genital warts

  • Usually diagnosed clinically
  • Molecular diagnostic procedures are available and are used to screen for cancer-causing genotypes of HPV
• HIV infection and AIDS


  • The signs and symptoms of acute HIV infection usually occur within several weeks to several months after infection
  • Initial symptoms include an acute, self-limited mononucleosis-like illness lasting 1 or 2 weeks
  • Other signs and symptoms include fever, rash, headache, lymphadenopathy, pharyngitis, myalgia, arthralgia, aseptic meningitis, retro-orbital pain, weight loss
• Viremia


  The presence of viruses in the bloodstream
• Viral load


  The number of viral nucleic acid copies per milliliter of serum or plasma
• Viral loads are used to monitor patients with HIV, hepatitis B and C, and the polyomaviruses BK and JC in transplant patients
• Epstein-Barr virus and cytomegalovirus viral loads are also useful in diagnosing infection caused by these two herpes viruses because both are latent viruses where simple detection may not signify that the virus is causing disease
• HIV


  Single-stranded RNA viruses in the family Retroviridae (retroviruses)
• Modes of HIV transmission

  • Direct sexual contact (homosexual or heterosexual)
  • Sharing of contaminated needles and syringes by intravenous drug abusers
  • Transfusion of contaminated blood and blood products
  • Transplacental transfer from mother to child
  • Breastfeeding by HIV-infected mothers
  • Transplantation of HIV-infected tissues or organs
  • Needlestick, scalpel, and broken glass injuries
• There is no evidence of HIV transmission via biting insects
• Most likely, HIV-1 first invades dendritic cells in the genital and oral mucosa. These cells then fuse with CD4+ lymphocytes (helper T cells) and spread to deeper tissues
• ELISA


  Enzyme-linked immunosorbent assay, the most commonly used screening test for HIV
• Western blot analysis


  A confirmatory test for HIV
• p24 antigen


  An HIV antigen detected by antigen detection procedures