Contact Diseases Epidemiology PDF

CONTACT DISEASES EPIDEMIOLOGY Community Medicine Department BACTERIAL DIAEASES Community Medicine Department Tetanus ◦Definition: Acute fatal bacterial infection, caused by exotoxin “tetanospasmin” produced by anaerobic tetanus bacilli. Characterized by muscle rigidity, hyper-reflexe...

CONTACT DISEASES EPIDEMIOLOGY Community Medicine Department BACTERIAL DIAEASES Community Medicine Department Tetanus ◦Definition: Acute fatal bacterial infection, caused by exotoxin “tetanospasmin” produced by anaerobic tetanus bacilli. Characterized by muscle rigidity, hyper-reflexes, neck & limb rigidity, stiff jaw “ trismus”, sardonic smile (risus sardonicus) & opisthotonos ◦Infectious Agent: Clostridium tetani, gram +ve, anaerobic spore forming organism “drum stick appearance”. Spore destroyed by steam under 120 degree. For 20—30 min or by gamma irradiation. ◦Reservoir of infection: Cl. Tetani widely distributed in soil, and dust, The bacilli found in herbivorous animal (cattle, sheep, horses) & excreted in their faces. Spore remain for many years in environment. - No man to man transmission  Tetanus ◦Mode of transmission: contamination of wound with tetanus spores. ◦Susceptibility & resistance: Age: All ages especially 5-40, new-born, Sex: males more frequently exposed. ◦IP: 3 – 21 days, may range from 1 day to several months, usually 14 days. ◦Types: traumatic tetanus, Puerperal tetanus, Tetanus Neonatorum, Otogenic tetanus, Idiopathic tetanus, Surgical tetanus. ◦Diagnosis: clinical features, laboratory confirmation difficult, C.tetani Abs sometimes detected in serum “may be from past immunization”, culture at site of infection “ organism often not recovered”  Leprosy ◦ Definition: chronic disease caused by mycobacterium leprae. It affects peripheral nerves, skin, muscles, eyes, bones, testes, & internal organs ◦ Infectious Agent: M. leprae acid-fast bacilli, have 20 Ag shared by pathogenic & non-pathogenic mycobacterium ◦ Reservoir of infection: man is only source, lepromatous (multibacillary), & borderline lepromatous cases most important source of infections in community. ◦ Portal of Exit: nose the most imp. exit, open skin lesion ◦ Period of communicability: Very long till patient start ttt. Infectivity declines after 90 days of dapsone, or 3 weeks with rifampicin. ◦ Mode of transmission: not yet established - Droplet, 2nd person – person close contact , others.  IP: 3-5 years in lepromatous cases, Tuberculoid shorter IP  Leprosy ◦ Susceptibility & resistance: - Age: peak of infection 10-20 years - Sex: male more affected - Immunity: abortive/self limiting, HLA linked gene have role ◦ Clinical Picture: Tuberculoid leprosy (paucibacillary leprosy) - Mild form: include red patches on skin, decrease in light –touch sensation in rash area, other forms associated sever pain, muscle weakness esp. hands, feet, skin stiffness dryness, loss of fingers, toes, eye problems, blindness enlarged nerves around elbow (ulnar), knee (peroneal) - Lepromtous leprosy: (multibacillary leprosy): asymmetrical skin rash found on face, ears, wrists, elbows, knees, buttocks. Skin rash small/ large, flat/ raised, light / dark. Other symptoms: thinning of eyebrow, eyelashes, thickened skin on face, nasal stuffiness, bloody nose, laryngitis, collapsing of the nose, swelling of LN in groin - armpits, scarring of tests & infertility, enlarged male breasts. Leprosy ◦Diagnosis: Clinical examination & inspection of lesions - Bacteriological (skin smear, nasal discharge or scraping) - Histamine test: intra-dermal injection of.1 ml of 1/1000 of histamine phosphate into a hypo-pigmented patch, in normal a wheel surround erythematous flare, in leprosy no response due to local nerve destruction. - Lepromine test:.1 ml intra-dermal injection of lepromine: nodule > 10 ml after 48 hrs, late after 7-10 days nodule > 5 ml Immunological: RIA, FLA- Abs, ELISA, monoclonal Ab.  Impetigo Contagious ◦Definition: contagious superficial skin infection seen mainly in children, it presented by irritating blisters, then pustules & erode leaving honey- color crust. Impetigo due to streptococcus pyogenes not generally associated with scarlet fever, but may cause GN. ◦Infectious Agent: various strains of streptococcus pyogenes, group A streptococci, staphylococcus aureus. ◦Reservoir of infection: human cases & carriers (different types). ◦Mode of transmission: organism enter though damaged skin & transmitted by direct contact with patient or asymptomatic/ nasal carrier ◦Period of communicability: If untreated remain infectious for weeks-months. Cases no longer infectious after 24 hours antibiotic treatment (ttt).  Impetigo Contagious ◦Susceptibility & resistance: Everyone susceptible to streptococcal & staphylococcal skin infection. Person suffer from eczema or dermatitis at great risk. IP: 1- 3 days for S. pyogenes, 4 – 10 days for S. aureus. Diagnosis: confirmed by isolation of organism from skin swabs, that allows confirmation of AB susceptibility.  Acute Bacterial Conjunctivitis ◦Definition: range from mild conjunctival redness to corneal infiltrate & visual disturbances in neglected cases. Purulent discharge present, trachoma should be suspected in presence of lymphoid follicle or diffuse conjunctival inflammation or in- turned eyelashes ◦Infectious Agent: H. influenza, streptococcus pneumonia most common causes, S. aureus, pseudomonas aeruginosa, N. gonorrhea, N. meningitides, Chlamydia occasionally. ◦Reservoir of infection: Cases & carriers (different types) ◦Mode of transmission: transmitted via contact with discharge of conjunctiva or URTI, Neonate's infection during vaginal delivery, sometimes flies. ◦Period of communicability: Infectious as there is discharge Acute Bacterial Conjunctivitis ◦Susceptibility & resistance: Everyone susceptible , repeated attacks by same or different bacteria possible, no immunity from infected mother to her infant. ◦IP: 1- 3 days, in trachoma 5 – 12 days. Diagnosis: mild conjunctivitis treated empirically. Microscopic examination of stained smear or culture of discharge required to differentiate bacterial from viral or allergic conjunctivitis  Sexually Transmitted Diseases ◦Definition: STDs or venereal diseases are infections acquire mainly through sexual contact. Some can be transmitted by non- sexual contact, as sharing needles, during delivery, during breast feeding. ◦5 Diseases were known as venereal diseases: gonorrhea, syphilis, less common granuloma inguinale, lymphoma-granuloma venerium, and chanchroid. ◦STD more sever in women: difficult diagnosis, sometimes 2 or more infections, less available ttt than men,, untreated cases lead to infertility, miscarriage, premature birth, infection of newborn. ◦Causes of increase STD incidence: use of contraceptives, emergence of drug resistant strains, symptomless carriers, highly mobile population, lack of public education, reluctance to seek treatment. ◦Period of communicability: - Curable STD: patient infectious until diagnosed & properly TT  Sexually Transmitted Diseases ◦Source of infection: cases with STD curable one (Chlamydia, gonorrhea, syphilis, trichomonas, vaginal infections) and incurable (genital herpes, genital warts “HPV”, Hep. B, HIV). - Incurable Carriers: HIV, genital herpes, genital warts “HPV”, Hep. B ◦Mode of transmission: through genital secretions: HIV, Syph. Hep. B through contact with infected blood as well as genital secretion. ◦Infective materials & exit: Semen, vaginal fluids, saliva, blood, skin, sores exudates. ◦Susceptibility & Risk factors: Age (20-29), male more frequent, women more serious, more in single, divorced than married, more in low socio-economic, population explosion, migration, women empowerment policies, delay marriage, family disruption, emotional & social disruption, drug addiction, smoking & alcoholism, decrease work opportunities.  Sexually Transmitted Diseases Incubation Period (IP) ◦ Gonorrhoea: 2 days after exposure – 1 month. ◦ Syphilis: chancre on average 21 days, may appear 10- 90 ◦ Chancaroid: 1 day – several wks, mostly 5-7 days after inf ◦ Chlamydia: 1 -3 wks after exposure to chlamydia. ◦ Trichomonas: women symptoms 5-28 days after exposure ◦ Scabies: 1 – 2 months for symptoms to appear. ◦ Genital warts: within 3 months of initial infection. ◦ Genital Herps: within 2 wks of exposure to virus. ◦ HIV: it may take 6 months after exposure before positive HIV Ab test ◦ Hepatitis B: 4 – 6 wks. ◦ Molluscum Contagiosa: 2 wks – 6 months.  VIRAL DISEASES Community Medicine Department  Rabies ◦Definition: it is a zoonotic disease transmitted from rabid animal to man. It is acute viral infection of CNS. ◦Infectious Agent: is rhabdovirus ◦Reservoir of infection: Dogs, cats, wolves, foxes, bats.. ◦Occurrence: 50.000 deaths / year worldwide ◦Mode of infection: 1. Common through bites of infected dogs, 2. Respiratory (rare): bates caves, or laboratory workers. ◦IP: in animal 20 – 60 days, in human variable according to site of bite varies from 10 days to 15 months with average 6 weeks ◦CP: Hydrophobia: difficult swallowing, painful muscle contraction (muscle of deglutition), There is reflex contraction at sight of liquids, Alternate periods of excitability up to mania and quietness, paralytic manifestation late or absent.  Hepatitis B ◦ Definition: Acute systemic infection cause liver pathology and transmitted by parenteral route, characterized by long IP & variable outcomes. ◦ Infectious Agent: Hepatitis B virus has 3 morphological forms (small spherical particles, tubules, Dane particles), HBsAg+ve has 3 forms, Dane is infectious, virus stable; survive for days on environ. surfaces, destroyed by autoclave (30-60 minutes). HBeAg+ve highly infectious. ◦ Reservoir of infection: man is the only reservoir (cases, carriers) ◦ Period of communicability: infected person is infective many weeks before onset of symptoms & remains infective through acute course, and chronic carrier state, which may persist for life. Persons who are HBV DNA positive highly infectious. ◦ CP: jaundice, anorexia, bad. discomfort, nausea, vomiting, lethargy, occasional rash, arthralgia.  Hepatitis B ◦Mode of transmission: - Transmission through per-cutaneous, per-mucosal exposure to contaminated blood, semen, vaginal fluids, during medical or dental procedures, tattooing, sharing razors toothbrushes, sexual contacts - Perinatal transmission at birth from infected mother ◦Susceptibility & resistance: All non-immune people are susceptible. Infection results in lifelong immunity in those who are not chronic carriers. Outcome age dependent: perinatal: 1-95% chronic, 1-5 years: 10-80% chronic, > 5years: 5-10% chronic. ◦High risk groups: Surgeons 50 times greater, blood transfusion, health & laboratory workers, homosexual, prostitutes, drug abusers, infant of infective mothers, immuno-compromised ◦IP: 45 – 180 days with average 60 -90 days. ◦Diagnosis: serological detection of HBsAg or HBV DNA  Hepatitis B Serology Interpretation Results Tests Susceptible negative HBsAg, antiHBc, antiHBs Immune due to infection negative HBsAg positive antiHBc, antiHBs Immune due to HB vaccination negative HBsAg, antiHBc positive antiHBs Acutely infected positive HBsAg, antiHBc, IgM anti- HBc negative antiHBs Chronic carrier positive HBsAg, antiHBc negative IgM anti-HBc, antiHBs HBV recovery, susceptible with negative HBsAg false +ve antiHBc, undetected positive antiHBc HBsAg in carrier, maternal antibody negative antiHBs  Hepatitis C ◦ Definition: Most infections Asymptomatic and acute infection may detected with elevated alanin aminotransferase (ALT) levels. 10-50% recover with clearance of the virus ◦ Infectious Agent: Hepatitis C virus RNA virus. Has at least 6 major genotype. ◦ Reservoir of infection: man is the only reservoir (cases, carriers) ◦ Period of communicability: Communicability occurs during acute clinical stage of HCV infection & indefinitely in chronic carrier stage. All HCV positive consider infectious, although risk is minimal in non viraemia (PCR) negative. ◦ Susceptibility & resistance: All non-immune people are susceptible. degree of immunity following infection is uncertain. If infection resolves & virus cleared, pt can infected by same or other genotype.Cohort studies shows that re-infection by HCV reduced after 1st HCV infection.  Hepatitis C ◦Mode of transmission: - Hepatitis C transmitted by blood contact: sharing injected needles in drug abusers, tattooing, in prisoners due to drug abusers & tattooing, health & laboratory workers. - sexual contacts rates of HCV are very low, the risk increase if HCV partner is immuno-compromised. - infected mother to baby 5-6%, occur in mothers HCV RNA +ve - Community, household transmission of HCV considered rare. ◦IP: ranges from 2 weeks to 6 months. Commonly 6-9 weeks after which serum ALT level rise. Current HCV antibody tests positive 2-3 months after exposure. ◦Diagnosis: HCV infection confirmed by HCV antibody test (EIA: enzyme immunoassay, RIBA: recombinant immunoblot assay): it can’t distinguish between patient who are currently infectious or recovered) ◦PCR detect HCV RNA: implies viraemia, ongoing infection, single –ve test not exclude infection, patient retested after 6-12 months.  Hepatitis D (delta hepatitis ) ◦Definition: It may be sever & always associated with HB V infection (co-infection). ◦Infectious Agent: Hepatitis D virus. A virus like particle consisting of a coat of hepatitis B virus. ◦Reservoir of infection: Human with HBV act as reservoir. ◦Period of communicability: similar to HBV. Patient infectious before onset of symptoms, acute disease & chronic carriers. ◦Mode of transmission: as HBV through blood infected blood & serous body fluid, sexual transmission less common, perinatal infection rare., ◦Susceptibility & resistance: all people susceptible to HB V infection, or have chronic hepatitis B. ◦IP: 2-8 wks. ◦Control & prevention: as HB V, vaccination against HBV prevents HDV  AID’s ◦Acute fatal diseases caused by retrovirus HIV characterize by opportunistic infections, neurological disorders, unusual malignancies. AID’s refers to late stage of HIV infection. ◦39.5 million infected with HIV worldwide. ◦Reservoir: cases & carrier. ◦Infected materials: blood, semen: high virus content. (CSF, tears, saliva, breast milk, urine, cervical & vagina secretion show low virus content). ◦ Mode of transmission: blood transfusion, drug abusers, sexual, trans-placental, needle stick, organ transplantation. ◦Susceptibility: age (20-50) , sex: homosexual, multiple partners PARASITIC DISEASES Community Medicine Department  Schistosomiasis ◦Definition: It is parasitic diseases in rural areas in Egypt & constitute major public health Problem ◦Infectious Agent: Sch. Haematobium cause urinary B, Sch Mansoni cause intestinal B, Sch Japonicum not in Egypt. ◦Source of infection: man passing egg ◦Infective Stage: Cercaria ◦Mode of infection: contact of skin with infected water during bathing, or manual irrigation. ◦Exit: faces or urine Inlet: skin especially between fingers ◦Infectivity Period: as long the case pass ova in stool, urine ◦Intermediate host: Bolinus trancatus, biomphalaria Snail ◦IP: about 4-6 weeks  Schistosomiasis ◦ CP: - Urinary B cause dysuria, terminal hematuria - Intestinal B cause dysenteric symptoms - Serious complication carcinoma of bladder, liver fibrosis. ◦ Diagnosis: Stool & urine examination to find OVA, rectal biopsy, intradermal test. ◦ Prevention & Control 1. Chemotherapy: paziquantal 40mg/kg with maximum dose 2.4 gms, Oxamniquine for Sch. Mansoni These drugs give as mass treatment to all population, or selective population (+ve cases) or selective group ttt (school children). 2. Snail control: cleaning of vegetation, proper banking, double canal system, nets prevent passage of snails, molluscides 3. Health education by mode of infection, how to prevent 4. Environmental: Pure H2 O, sanitary WC, mechanical irrigation In Egypt: decrease prevalence due to free examination, mass treatment