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General concepts: 1. Epidemiological triangle: the traditional model of infectious disease causation, which has three components: an external agent, a susceptible host, and an environment that brings the host and agent together so that disease occurs. An external agent (organism): - Ability of the agent to survive outside the host/ in the environment - Ability of the agent to change its antigenicity to escape host’s immunity such as influenza virus A susceptible host: - Personal factors such as low immunity, extremely age and malnutrition status - Person with genetic predisposing factors - Risk behaviors such as smoking, alcohol drinking, unsafe sex and some recreational activities An environment: - Some favorable physical/ biological factors for vectors such as ambient temperature, specified climate and disaster - Limited social welfare/ poverty - Displacement, immigrant 2. Isolation VS. Quarantine: Isolation: separation, for the period of communicability, of infected persons (sick person) or animals from others under such conditions as to prevent or limit the transmission of the infectious agent from those infected to those who are susceptible or who may spread the agent to others. Quarantine: restriction of the activities of well persons or animals who have been exposed to a case of communicable disease during its period of communicability (i.e., contacts) to prevent disease transmission during the incubation period if infection should occur. Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford University Press. Kindle Edition. 3. Direct VS. Indirect transmission: Direct transmission: direct and essentially immediate transfer of infectious agents to a receptive portal of entry through which human or animal infection may take place. This may be by direct contact such as touching, kissing, biting, or sexual intercourse or by the direct projection (droplet spread) of droplet spray. Indirect transmission: Vehicle-borne: Contaminated inanimate material or objects (fomites--e.x., sharing needles) such as toys, handkerchiefs, soiled clothes, bedding, cooking or eating utensils, and surgical instruments or dressings (indirect contact); water, food, milk; biological products including blood, serum, plasma, tissues, or organs; or any substance serving as an intermediate means by which an infectious agent is transported and introduced into a susceptible host through a suitable portal of entry. The agent may or may not have multiplied or developed in or on the vehicle before being transmitted. Vector-borne: (a) Mechanical: Includes simple mechanical carriage by a crawling or flying insect through soiling of its feet or proboscis or by passage of organisms through its gastrointestinal tract. This does not require multiplication or development of the organism. (b) Biological: Propagation (multiplication), cyclic development, or a combination of these (cyclopropagative) is required before the arthropod can transmit the infective form of the agent to humans. Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford University Press. Kindle Edition. Hep B= direct and indirect, Hep C= indirect (needle exchange) Rabies= direct transmission from animal to human Malaria= indirect (mosquito), a transmission cycle in between human and mosquito Lepto= indirect reservoir. host is animals 4. Horizontal VS. Vertical transmission: Horizontal transmission: the transmission of an infectious agent, such as bacterial, fungal, or viral infection, between members of the same species that are not in a parent-child relationship. Reference: http://en.wikipedia.org/wiki/Horizontal_disease_transmission Vertical transmission: (Syn: intergenerational transmission) the transmission of infection from one generation to the next, especially of HIV infection from mother to infant prenatally, during delivery, or in the postnatal period via breast milk. Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford University Press. Kindle Edition. Vertical -Perinatal - Placental - Transplacental such as “TORCHS” - Toxoplasmosis, Rubella, Cytomegalovirus, Herpes, Syphilis 5. Infectivity VS. Pathogenicity VS. Virulence Infectivity: the proportion of people who are exposed to an agent and become infected. Pathogenicity: the proportion of people who are infected by an agent and then develop clinical disease. Virulence: the measure of severity of a disease, expressed as the proportion of people with the disease who become extremely ill or die. * Are exposed – Become infected—Developed clinical disease—Become extremely ill/die* * Measle has high infectivity. TB has low pathogenicity. Rabies has high pathogenicity. HIV has low infectivity, but high pathogenicity. 6. Zoonosis/ Enzootic or Epizootic: a disease infection, or infestation transmitted under natural conditions from vertebrate animals to humans. Examples include rabies and plague. Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford University Press. Kindle Edition. 7. Epidemic VS. Endemic VS. Pandemic: Epidemic: [from the Greek epi (upon), dēmos (people)] The occurrence in a community or region of cases of an illness, specific health-related behavior, or other health-related events clearly in excess of normal expectancy. The community or region and the period in which the cases occur must be specified precisely. The number of cases indicating the presence of an epidemic varies according to the agent, size, and type of population exposed; previous experience or lack of exposure to the disease; and time and place of occurrence. Endemic: the constant occurrence of a disease, disorder, or noxious infectious agent in a geographic area or population group; it may also refer to the chronic high prevalence of a disease in such area or group. Pandemic: an EPIDEMIC occurring over a very wide area, crossing international boundaries, and usually affecting a large number of people. Only some pandemics cause severe disease in some individuals or at a population level. Characteristics of an infectious agent influencing the causation of a pandemic include: the agent must be able to infect humans, to cause disease in humans, and to spread easily from human to human. Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford University Press. Kindle Edition. 8. Passive VS. Active immunity: Passive immunity: conferred by an antibody produced in another host and acquired naturally by an infant from its mother or artificially by administration of an antibodycontaining preparation (antiserum or immune globulin). Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford University Press. Kindle Edition. Active immunity: A type of immunity or resistance developed in an organism by its own production of antibodies in response to an exposure to an antigen, a pathogen or to a vaccine. Reference: http://www.biology-online.org/dictionary/Active_immunity Disease Legionnaires’ disease Causative agent Bacterium Reservoir Man-made water supplies that aerosolized water Mode of Transmission Air-borne spread Incubation period 2-10 days (most often 5-6 days) Risk factors Aging, Compromised immunity, Chronic Lung Disease (COPD), Deficiency of Immunity, Male Preventive measure Proper maintenance and disinfection of man-made water supplies Vaccination No Disease Syphilis Gonorrhea Chlamydia Causative agent Bacterium Reservoir Humans Mode of Transmission Sexual transmission Vertical/ perinatal transmission Blood transfusion Sexual transmission Vertical/ perinatal transmission Sexual transmission Vertical/ perinatal transmission Incubation period 10 days - 3 months 1-14 days (Usually 3 weeks) 7-14 days Risk factors All people Health professionals MSM Sex workers Sexually active youth Sexually active persons Preventive measure Safe sex Screening: STI group, sex worker, pregnant Safe sex Screening: STI group, sex worker Safe sex Screening: STI group, sex worker, all sexually active women aged 25 years or younger Vaccination No Disease HPV (Human Papillomavirus) Causative agent Virus Reservoir Humans Mode of Transmission Sexual transmission Vertical/ perinatal transmission Fomites HSV (Herpes Simplex Virus) Sexual transmission Vertical/ perinatal transmission Contact with HSV in saliva or genital secretions Incubation period 2 - 3 months 2 - 12 days Risk factors Children Sexually active young adults Immunosuppressed patients Neonates born to women with genital HSV Unprotected sexual intercourse Preventive measure Safe sex : condom may decrease risk Safe sex Health education and personal hygiene Cesarean section Vaccination Yes: Gardasil No Disease HIV (Human Immonodeficiency Virus)/ AIDS (Acquired Immune Deficiency) Causative agent Virus Reservoir Humans Mode of Transmission Person to person Unprotected sexual intercourse Needle/ syringe sharing Vertical transmission Breast feeding Blood transfusion Incubation period Less than 1 month, Variable Risk factors Unprotected sexual intercourse Injecting drug users Sex workers MSM Health care workers Preventive measure Safe sex Prevention of injecting drug use HIV testing and counselling: high risk group Postexposure prophylaxis Preventing mother to child transmission Universal HIV screening of pregnant women Antiretrovirals Elective cesarean section Avoid breast feeding Autologous transfusion Universal precaution Vaccination No Disease HAV HBV HCV Causative agent Virus Reservoir Humans (Primary) A-Anus B-Baby/Booty/Blood C-Cooker Mode of Transmission Ingestion of fecally Perinatal/ vertical contaminated food/ transmission water Percutaneous or mucosal exposure to infective body fluid (Direct transmission) Injection drug use with sharing of needles (Indirect transmission) Receipt of blood/ Sexually transmission (Direct transmission) blood products from unscreened donor (Indirect transmission) Injection drug use with sharing of needles (Indirect transmission) Incubation period 28 - 30 days 60 -90 days (usually 45180 days) 2 weeks - 6 months (6 - 9 weeks) Risk factors Living in/ travelling to high endemic areas Sexual partner or household contact Recipients of unscreened donated blood MSM Close personal contact to patients Preventive measure Vaccination Injection drug users Health care and public safety work Vaccination Vaccination Proper sanitation Risk-based screening Blood bank screening test Single use needle Standard precaution for blood Yes Yes No Disease Dengue Malaria Causative agent Virus Protozoa parasites Reservoir Humans Humans Mosquito Mosquito/ Apes(??) Monkey Monkey (P.knowlesi)(??) Bite of infective mosquitoes (day-biting species) Bite of infective female mosquitoes (night-biting species) Mode of Transmission Incubation period 3 -14 days (commonly 4 -7 days) PF: 9 - 14 days PV & PO: 12 -18 days (Some) PV: 6 - 12 months PM: 18 - 40 days Risk factors Living in endemic areas esp. children Living in endemic areas universal except in human with specific genetic traits Perinatal transmission Preventive measure Vaccination Education A - Aware of the risks Prevention of bites from the vector mosquito B - Avoid being bitten by mosquitoes Vector control eliminate larval habitats C - Chemoprophylaxis No No D - Immediate seek diagnosis and treatment Use ITN, LLIN, mosquito repellent. Disease Tuberculosis Influenza Causative agent Bacterium Virus Reservoir Humans Aquatic birds Bats Influenza A - Pig, Horses, and Seals Humans Mode of Transmission Infective droplet nuclei via coughing or sneezing Infective droplet nuclei via coughing or sneezing Incubation period 2 - 10 weeks 2 days Risk factors Exposure to active pulmonary TB All age group esp. extremely age Compromised immunity Extremely age Obesity Compromised immunity Preventive measure Public education Public education BCG vaccine Vaccination Prompt diagnosis and treatment Prophylaxis: anti-viral antigen Infective control measure in health care setting Eliminate bovine tuberculosis Vaccination Yes Disease Leptospirosis Causative agent Bacterium Reservoir Renal tubule/ genital tract of wild and domestic animals rats swine cattle dogs raccoons Mode of Transmission Contact of skin or mucous membranes with moist soil or vegetation contaminated with the urine of infected animal (Indirect contact) contaminated water (Indirect contact) urine, fluids, or tissues of infected animals Incubation period 5 -14 days (2 - 30 days) Risk factors Living in endemic area Occupational workers Yes Preventive measure Public education Protect workers in hazardous occupations Control rodents and reservoir wildlife populations Immunization of farm and pet animals/ people Vaccination Yes Disease Small pox Anthrax Causative agent Virus Bacterium Reservoir Humans Herbivores, both livestock and wildlife Mode of Transmission Person-person via respiratory droplets or skin inoculation Transmitted from infected animals to humans Incubation period 7 - 19 days (10 - 14 days) Cutaneous: 1 - 12 days (5 - 7 days) Inhalation: 1 - 43 days GI: 1 - 6 days Injection: 1 -10 days Risk factors Preventive measure Unvaccinated persons Occupational workers Small pox research scientist Heroin injection Vaccination Vaccination persons and animals Prevention and control in animals Vaccination Yes Yes Disease Ebola hemorrhagic fever Causative agent Virus Reservoir Forest/ cave-dwelling fruit bats Mode of Transmission Person-person transmission occurs through direct contact with infected body fluid Nosocomial infection Semen Incubation period 5 - 15 days Risk factors All ages People working with wildlife Health care workers Preventive measure Strict procedures for isolation Vaccination No Disease Hantaviral diseases (HPS) Causative agent Virus Reservoir Deer mouse Humans (accidental hosts) Mode of Transmission Aerosol transmission from rodent excreta Incubation period 2 weeks Risk factors Persons in rural populations who come into contact with rodents Occupational workers Health care workers Preventive measure Disinfection Vaccination Vaccination Yes 9. Legionnaires’ Disease: Pneumonia occurred in persons who attended conventions at a hotel on Broad Street was legionnaire disease. The outbreak which occurred in the summer caused 182 cases, of which, 29 cases were fatal. Of the 182 legionnaire cases, 142 were males and patientsʻ mean age was 54.7 years old. Mode of transmission was airborne spread. There was no evidence of transmission from person to person, food-borne, or water-borne. There was a consistency with the association of illness with time spent in the lobby and on the sidewalk in front of the hotel, smoking habit (patients are predominantly male), older age, and immunocompromised condition. 10. Bacterial STDs: * Five leading National notifiable infectious disease 2012 US. Hawaii 1. Chlamydia 1. Chlamydia 2. Gonorrhea 2. Gonorrhea 3. Salmonellosis 3. Salmonellosis 4. Syphilis 4. TB 5. HIV 5. Invasive pneumococcal disease Age and Sex- Chlamydia Gonorrhea Syphilis Predominantly Infection rate has Predominantly male specific Rates Epidemiological Trends sexually active, been decreasing young female group both in the US and (14-24 years). Hawaii. (MSM cases in HI: 74%) among middle age (42 years in HI). The prevalence (6.8 %) among female 14-24y is 3 times higher than those 25-29 years). In HI, more males than females. In US, proportion of female cases has been decreasing; but it is increasing in HI (from 4% in early 2000s to 20% in late 2000s). 2.8 million infections each year. Most infected females are asymptomatic; most infected males are symptomatic. Prevalence among African American has 5 times higher than the rate among nonHispanic white. Among females, mostly young age groups (15y < 2024y> 30y). Rapid spread of drug resistance. Racial and ethnic group variations exist (African American population was 6 times higher than the rate among nonHIspanic white group). Up to 70% of infected females and 50% of males are asymptomatic. Condom Efficacy* Can protect against Chlamydia 90+% Can protect against Gonorrhea 90+% Limited efficacy for Syphilis protection * Reference: Condoms and STDs: Fact Sheet for Public Health Personnel, CDC 11. Viral STDs: Epidemiological Trends Incidence & Prevalence natural history HPV HSV Most common STD in the U.S. ~ 50-80% of sexually adults will be infected at least once Steadily trends in HPV-2 seroprevalence Impact of HPV vaccine: Reduction in HPV prevalence was found in Seroprevalence: Overall 15.7%, increase with increasing age 14-19 year old females Most significant agent that cause cervical and anal cancer Prevalence among females (survey): Overall 39.8%, Peak 2024 years Infection usually goes away completely by itself. Persistent infection related to: older age, high risk type, and infection with more than one type. Condom Efficacy Most cases go unrecognized and undetected It is because 80% of case are asymptomatic. Recurrences are more frequent within the first few years but tend to decrease over time Condom use: Limited efficacy Hazard Ratio 0.3 for CSIL Hazard Ratio 0.74 Hazard Ratio 0.0 for Intraepithelial for infection lesions * Gardasil vaccine: Quadrivalent vaccine which targets HPV type 6, 11, 16, 18. Responsible for 70% of cervical cancer (16 & 18) and 90% of external genital wart (6 & 11). RCT demonstrated 100% efficacy against HPV-related disease and 89% protection against HPV infection. 12. HIV/AIDS: Descriptive epidemiology Risk behavioral groups Globally/ Internationally U.S. Hawaii 35 million living with HIV 1.2 million persons living with HIV Male 89% Female 11% New infection has been decreased. However, HIV incidence and HIV-related mortality have increased in Eastern Europe and Central Asia driven by injection drug use and needle sharing Female 52% Transmission: Predominantly due to heterosexual sex 50,000 new infections/year (stable) Male 80% Female 20 % Male: 80% MSM, 5% IDU, 6% MSM+IDU, 11% Heterosexual Transmission: MSM 71% IDU 8% MSM+IDU 7% Heterosexual 7% Undetermined 6% Transfusion 1% Perinatal < 1% Hemophilia < 1% Female: 85% heterosexual, 14% IDU Africanamerican 47% White 28% Prevention Caucasians 57% Asians 15% Hawaiians 11% Hispanics 7% Africanamerican 5% Heterosexual transmission Condom Male circumcision Antiretroviral therapy for HIV-infected person Pre & Post exposure prophylaxis General Testing of the blood supply MSM Condoms Antiretroviral therapy for HIV-infected person Pre & Post exposure prophylaxis Mother to child transmission Antiretroviral therapy C-section Avoid breast feeding Injection drug use Do not share equipment Syringe exchange programs Opiate substitution Pre & Post exposure prophylaxis *PrEP: Uninfected person takes HIV antiretrovirals, daily May prevent replication of HIV infection Candidates: MSM Transgender individuals Heterosexual women and men - serodiscordant, multiple partners and commercial sex workers Injection drug users 13. Viral hepatitis: Natural history HAV HBV HCV 2,700 new infections in U.S. 18,800 new infections in U.S. up to 1.4 million chronic infections (Most people do not know they have it) 16,500 new infections in U.S. up to 5 million chronic infections 75 - 85 % of infected adults will not resolve Acute infection only Once resolved -- lifelong immunity Possible chronic Chronic infection 5% of infected adults will develop to chronic stage. 90% of infected children will develop to chronic stage. Once resolved -- lifelong immunity Symptoms: Acute: Infant ~0%(Carrier) child 10%(Carrier) Adult 30% Symptoms: None ~80% Treatment: up to 80% cure If resolve: no protection Highly infectious -stable in environment for 4 days - 6 weeks Treatment: no cure Highly infectious -- stable in environment for 7 days 14. Influenza: Anti-genetic drift: Molecular changes in virus (small change) Occur constantly Anti-genetic shift: The genetic change (major change) that enables a flu strain to jump from one animal species to another, including humans (e.g., Swine flu, bird flu) Because people have no immunity, this can cause pandemic. (Source: class handout of NIH ) Antigenic markers for influenza: Three types - A , B , C Flu strains based on surface antigen - Hemagglutinin (HA), Neuraminidase (NA) 15.Dengue: * Epidemiological triangle Environment: Rainfall, temperature, flight range, female density, feeding behavior Area and indoor spray, source reduction, genetic modification Human: Movement, exposure, age, sex, urbanization, water storage practices Bug spray, long pants, screen windows/ bed nets Virus: endemic or epidemic strain, mutation *Antigenic markers DENV 1-4 * Identify risk factors for DHF/DSS Children High viral load and elevated cytokines and chemokines are associated with DHF * Antibody dependent enhancement ( Immune enhancement) – - once infected one strain of dengue virus, it will increase antibody and the prior infection to heterogenous dengue increases a great risk. This causes the problem on the vaccine developing processes because the vaccine has to be effective for all strains of virus in order not to cause the immune enhancement issue. *Epidemiological trend of occurrence Global resurgence (500-100 million annually, 75% is SEA and West Pacific) 16. Tuberculosis: * Latent VS. Active TB Latent TB (LTBI) (Goal = prevent future active disease) = TB Infection = No Disease = NOT SICK = NOT INFECTIOUS Active TB (Goal = treat to cure, prevent transmission) = TB Infection which has progressed to TB Disease = SICK (usually) = INFECTIOUS if PULMONARY (usually) = NOT INFECTIOUS if not PULMONARY (usually) *Factors increased TB disease Biomedical HIV infection* (strongest risk) DM Tobacco Malnutrition Silicosis Malignancy Environmental Indoor air pollution Inadequate ventilation Socioeconomic Overcrowding Urbanization Migration Poverty Population explosion * Epidemiology of TB Hawaii Epidemiology # 1 in the nation, but improving 90% of TB cases in Hawaii are foreign born U.S. Globally 1990 - TB re-emerges, co-infection with HIV After disappearing from the world public health agenda in the 1960s and 1970s, TB returned in the early 1990s for several reasons, including the emergence of the HIV/AIDS pandemic and increases in drug resistance. 2010 Lowest # of reported cases in U.S. *MDR-TB: That is, strains resistant to isoniazid and rifampicin This emerging problem was linked to improper prescribing practices, lack of patient adherence to treatment and irregular supply low quality of drugs 17. Malaria: P. Falciparum Natural history P. Vivax Roughly Equal prevalence in most of Asia and Central America, where transmission is low and seasonal. Most prevalence P. Ovale P. Malariae Mainly in subSaharan Africa Similar distribution with PV but is rare Second most prevalence Asexual cycle in blood: 48 h Asexual cycle in blood: 72 h Some hepatic form remain dormant as hypnozoites for 2 weeks - more than a year Ass. general seizures Period of communicability (Untreated or insufficiency treated patients may be a source of mosquito infection) < 1 year up to 5 years Several decades 18. Leptospirosis: *Epidemiology in Hawaii Highest incidence rate in U.S. Kauai > Hawaii > Molokai Male > Female A significant shift from peak occurrence during the drier summer months to the wetter winter months Highest age specific rate 20 - 29 years Recreational > Occupational > Habitational 19. Smallpox and Anthrax <Natural History> Smallpox Malaise, headache, rashes on extremity Risk groups: caregiver, nursing person Incubation period: 7-19 days (commonly 10-14 days) Up to 4 days one can intervene after infected. Immunization after exposure will significantly decrease. 20-50% case fatality rate. Highly infectious, highly pathogenic, highly virulent. Anthrax Cutaneous (get lesion in cutaneous anthrax, don’t die from it) Risk factors: slaughtering animals, close to herder. disease (veterinarians, agriculture and wildlife worker in developed country, persons working with animal hair or hide) Incubation period: 5-7 days. *Characteristics/ features that led the CDC to classify as “category A” bioweapon agents Feasibility of large-scale aerosol exposing High infectivity among unvaccinated population Bioweapons can be produced at low tech facility by independent groups. 9 points to remember regarding Anthrax (zoonotic bacteria – B. Anthracis, spores)/ Small pox (variola virus) 1. Biological weapons: Small pox is more severe since it is difficult for Anthrax to transmit via person to person 2. Both diseases can be prevented by vaccination. 3. Anthrax: Transmission- Cutaneous (most common but least severe) --- contacted with infected animal, Gastro-intestinal --- consuming inadequately cooked meat, Inhalation (most severe form, with > 85% of case mortality) --- risky in industrial processes 4. Anthrax: Reservoir-herbivores/ spores, which contaminated soil, may remain viable for year 5. Anthrax: Prevention-vaccinated high-risk persons and animals/ using proper disinfected protocol for destroying B. Anthracis spores 6. Small pox: No known human cases since 1978, eradication was done primarily by vaccination. 7. Small pox: Transmission: primary mode of infection is contact with infected droplet. 8. Small pox: Reservoir-only human 9. Small pox: Prevention-vaccination with in 4 days of exposure prevents clinical illness. 20. Ebola virus disease: * Classified as a “Category A” (high-priority agent that poses a risk to national security) bioweapon agent in 1999 by the CDC based upon: Potential to cause widespread illness and death Ease of dissemination or person-to-person spread (Only Ebola and Smallpox, not Anthrax) Potential for major public health impact Requirement for special public health preparedness 21.Hantavirus pulmonary syndrome: * A case control study during the outbreak in the Southwestern U.S. found that these factors were associated with risk of developing HPS: More small rodents at case household Hand plow Clean feed storage areas plants clean animal sheds RESERVOIR OF INFECTION 1. Any person, animal, arthropod, plant, soil, or substance, or combination of these in which an infectious agent normally lives and multiplies, on which it depends primarily for survival, and where it reproduces itself in such a manner that it can be transmitted to a susceptible host. 2. The natural habitat of the infectious agent. Source: A Dictionary of Epidemiology (Kindle Locations 12197-12208). Oxford University Press. Kindle Edition.