Epidemic Disease Occurrence PDF

EPIDEMIC DISEASE OCCURRENCE TOPIC 13 Level of disease Sporadic Epidemic Outbreak Pandemic Endemic Hyperendemic The baseline The baseline  The amount of a particular disease that is usually present in a community In the absence of intervention and assuming that the level...

EPIDEMIC DISEASE OCCURRENCE TOPIC 13 Level of disease Sporadic Epidemic Outbreak Pandemic Endemic Hyperendemic The baseline The baseline  The amount of a particular disease that is usually present in a community In the absence of intervention and assuming that the level is not high enough to deplete the pool of susceptible persons, the disease may continue to occur at this level indefinitely. Thus, the baseline level is often regarded as the expected level of the disease. Disease Occurrence Some diseases are so rare in a given population that a single case warrants an epidemiologic investigation (e.g., tetanus, rabies, plague, polio) While other diseases occur more commonly so that only deviations from the norm warrant investigation. Rabies is a vaccine- preventable, zoonotic, viral Tetanus- a bacterial disease disease affecting marked the central nervous by rigidity and spasms of the voluntary muscles. system. Polio Disabling and life-threatening disease caused by the poliovirus. The virus spreads from person to person and can infect a person's spinal cord, causing paralysis. Disease Occurrence Sporadic refers to a disease that occurs infrequently and irregularly. Occur infrequently, irregularly, or occasionally, from time to time in a few isolated places, with no discernible temporal or spatial pattern E.g. tetanus, rabies, and plague Disease Occurrence Endemic refers to the constant presence and/or usual prevalence of a disease or infectious agent in a population Hyperendemic refers to persistent, high levels of disease occurrence within a geographic area. Disease Occurrence Occasionally, the amount of disease in a community rises above the expected level. Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area. Outbreak carries the same definition of epidemic, but is often used for a more limited geographic area. Disease Occurrence Cluster refers to an aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known. Pandemic refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people.  Epidemic In adequate numbers, and the agent can be effectively conveyed from a source to the susceptible hosts. More specifically, an epidemic may result from: A recent increase in amount or virulence of the agent, The recent introduction of the agent into a setting where it has not been before, An enhanced mode of transmission so that more susceptible persons are exposed, A change in the susceptibility of the host response to the agent, and/or Factors that increase host exposure or involve introduction through new portals of entry. Epidemic Patterns  A common-source outbreak is one in which a group of persons are all exposed to an Epidemic infectious agent or a toxin from the same source. Patterns Point-source outbreak  If the group is exposed over a relatively brief period, so that everyone who becomes ill does so within one incubation period. Epidemic Patterns Point-source outbreak E.g. The epidemic of leukemia cases in Hiroshima following the atomic bomb blast and the epidemic of hepatitis A among patrons of the Pennsylvania restaurant who ate green onions each had a point source of exposure. Figure 1. Hepatitis A Cases by Date of Onset Epidemic Patterns In some common-source outbreaks, case-patients may have been exposed over a period of days, weeks, or longer. Continuous common-source outbreak  the range of exposures and range of incubation periods tend to flatten and widen the peaks of the epidemic curve. Figure 2. Diarrheal Illness in City Residents by Date of Onset and Character of Stool Epidemic Patterns The epidemic curve of an intermittent common-source outbreak often has a pattern reflecting the intermittent nature of the exposure. Epidemic Patterns A propagated outbreak results from transmission from one person to another. Usually, transmission is by direct person- to-person contact, as with syphilis. Transmission may also be vehicle-borne (e.g., transmission of hepatitis B or HIV by sharing needles) or vector-borne (e.g., transmission of yellow fever by mosquitoes).  Epidemic Patterns In propagated outbreaks, cases occur over more than one incubation period. In Figure 3, note the peaks occurring about 11 days apart, consistent with the incubation period for measles. The epidemic usually wanes after a few generations, either because the number of susceptible persons falls below some critical level required to sustain transmission, or because intervention measures become effective. Figure 1.23 Measles Cases by Date of Onset, October 15– January 16. Epidemic Patterns Some epidemics have features of both common-source epidemics and propagated epidemics. The pattern of a common-source outbreak followed by secondary person-to-person spread is not uncommon. These are called mixed epidemics. For example, a common-source epidemic of shigellosis occurred among a group of 3,000 women attending a national music festival. Many developed symptoms after returning home. Over the next few weeks, several state health departments detected subsequent generations of Shigella cases propagated by person-to-person transmission from festival attendees.  Epidemic diseases are illnesses that see a sudden Epidemic increase in the number of cases above what is normally Disease expected in a specific area. Occurrence in Key characteristics: rapid Industrial spread, a defined geographic Hygiene area, and often a short duration.  Respiratory Diseases: Tuberculosis, COVID-19, Legionnaires' disease. Types of Gastrointestinal Diseases: Epidemic Norovirus, Salmonella. Diseases in Industrial Vector-Borne Diseases: Malaria, Dengue fever in certain industrial Settings environments. Bloodborne Diseases: Hepatitis B and C, HIV.  Airborne Transmission: COVID-19 and tuberculosis spread through aerosols and droplets. Contact Transmission: Spread through surfaces and person-to-person contact. Routes of Transmission Vector Transmission: Insects and rodents in industrial environments. Waterborne Transmission: Contaminated water sources in industrial processes. Risk Factors in Industrial Settings High-Density Work Environments: Close quarters and inadequate ventilation. Poor Sanitation: Insufficient hygiene practices and facilities. Occupational Hazards: Specific risks related to certain industries, such as healthcare, food processing, and agriculture. Globalization and Travel: Increased movement of goods and people, spreading diseases across borders. Preventive Measures Engineering Controls: Administrative Improved ventilation Controls: Policies for systems, isolation of sick leave, travel contaminated areas, and restrictions, and hygiene use of protective practices. barriers. Personal Protective Equipment (PPE): Vaccination Programs: Masks, gloves, gowns, Immunization for workers and other protective against certain diseases. gear. Regular Screening and Surveillance: Monitoring the health of workers to detect early signs of disease. Case Studies COVID-19 Pandemic: Measures taken in various industries to mitigate the spread of the virus. Legionnaires' Disease in Industrial Cooling Systems: Case studies on outbreaks and mitigation strategies. Tuberculosis in Mining and Construction: Historical and modern approaches to control TB in these settings.  Assessment Training and and Monitoring: Education: Regular risk Informing assessments workers about Role of and monitoring disease risks of workplace and preventive conditions. measures. Industrial Hygienists Policy Development: Crisis Management: Responding to Creating and outbreaks and enforcing health coordinating with and safety public health policies. authorities.  Climate Change: Impact on vector-borne diseases and new health risks. Antimicrobial Resistance: Emerging Challenges in controlling infectious diseases. Threats Global Health Trends: Monitoring global disease patterns and preparing for potential industrial impacts. Thank you