Chapter 9 Communicable Diseases PDF

Chapter 9 Communicable Diseases Copyright ©2024 F.A. Davis Company  Communicable Disease Across Time  1900 Communicable diseases (CD) leading cause of death  1950 to 196...

Chapter 9 Communicable Diseases Copyright ©2024 F.A. Davis Company  Communicable Disease Across Time  1900 Communicable diseases (CD) leading cause of death  1950 to 1960 Measles, mumps endemic in school children  End of the 20th century: emerging CDs  21st-century: CDs remain a main reason for morbidity and mortality Newly emerging CDs Copyright ©2024 F.A. Davis Company  Global Causes of Death (2020)  Communicable diseases in top 10 causes of death: COVID-19 Lower respiratory infections Diarrheal diseases Tuberculosis Copyright ©2024 F.A. Davis Company  Communicable Disease and Surveillance  Public health’s responsibility, local to global surveillance of diseases Epidemic ‒ Significant increase in a disease Endemic ‒ Usual number of cases of a disease within a population Pandemic ‒ Epidemics occurring around the globe Copyright ©2024 F.A. Davis Company  Communicable Diseases and Nursing Practice  Care to patients  Preventative measures Personal protective equipment (PPE) Proper cleaning of equipment Preventing transmission to coworkers, self, and other patients  Understanding communicable diseases Individual level Population level Copyright ©2024 F.A. Davis Company  Populations and Communicable Diseases  Caring for the patient requires considering the implications for the population, including understanding The infectious agent Who is at risk Mode of transmission Prevention Treatment Copyright ©2024 F.A. Davis Company  Communicable Diseases and the Burden of Disease  Today, improvements in technology and transportation have brought people closer together.  Increase in emerging and reemerging CDs Zika Ebola Tuberculosis SARS-CoV-2 Copyright ©2024 F.A. Davis Company  Infectious Respiratory Diseases  Many different CDs (bacterial and viral) can affect the respiratory system. Chicken pox Diphtheria Rubella Influenza  Vaccinations = decline in these diseases Copyright ©2024 F.A. Davis Company  Parasitic Diseases: Malaria  Malaria is a global health problem: Spread by the bite of an infected mosquito Found in subtropical areas Affects greater than one-half of the world’s population Around 172 million cases worldwide in 2020 Copyright ©2024 F.A. Davis Company  Diarrheal Disease (continued) Most common route for transmission is the fecal–oral route. ‒ Good hand hygiene, especially hand washing, and soap alone can reduce the incidence of diarrheal disease by as much as 48%. ‒ Efficient sanitary systems and safe drinking water also play a huge role in preventing diarrheal diseases. Copyright ©2024 F.A. Davis Company  Diarrheal Disease  Globally, 1.7 billion cases of diarrheal disease worldwide each year Second-leading cause of death for children under 5 years of age Copyright ©2024 F.A. Davis Company  Diarrheal Disease Causes and Transmission  Caused by Bacteria Virus Protozoa  Mode of transmission Waterborne (for example, cholera) Foodborne/person to person (for example, Escherichia coli) Copyright ©2024 F.A. Davis Company  Emerging Communicable Diseases  Response to such diseases results in a burden on the economic, social, and health-care systems of countries  Pandemics require a coordinated early response Copyright ©2024 F.A. Davis Company  Eradicated and Reemerging Communicable Diseases  Smallpox has been eradicated and some CDs are close to eradication. Polio Dracunculiasis (Guinea Worm)  Other CDs are reemerging in forms that are resistant to drug treatments. Malaria Tuberculosis Bacterial pneumonias Copyright ©2024 F.A. Davis Company  Tuberculosis  Tuberculosis (TB) Caused by Mycobacterium tuberculosis 1889: recognized as preventable, not inherited 1998: TB elimination project  The World Health Organization (WHO) End Strategy and the United Nations’ Sustainable Development Goals Aim to have a 90% reduction in TB deaths and 80% reduction in TB incidence by 2030 Copyright ©2024 F.A. Davis Company  Communicable Disease Transmission  Three key components needed in the transmission cycle are 1. Agent 2. Host 3. Environment Copyright ©2024 F.A. Davis Company  The Cycle of Transmission  The epidemiological triangle is expanded to help disease researchers understand the cycle of transmission. Copyright ©2024 F.A. Davis Company  Agent Characteristics  Agent or pathogen: the infectious organism that causes the disease  Six general categories of pathogens: 1. Bacteria 2. Rickettsia 3. Viruses 4. Mycoses 5. Protozoa 6. Helminths Copyright ©2024 F.A. Davis Company  Agent Characteristics (continued) Copyright ©2024 F.A. Davis Company  Specific Agent Characteristics  Infectivity of the agent: capacity of an agent to enter and multiply in the host  Pathogenicity: capacity of the agent to cause disease in the human host  Virulence: degree of pathogenicity quantitatively  Toxigenicity: ability to release toxins that contribute to disease within the human host  Antigenicity: ability to produce antibodies in the human host Copyright ©2024 F.A. Davis Company  Environmental Characteristics  Environment: conditions external to the host and agent associated with the transmission of the agent  Reservoir: where the agent resides Human Animal Water, food, air, or soil Copyright ©2024 F.A. Davis Company  Human Reservoir  A person who is acutely ill OR  A person who is a carrier: Incubating carrier: someone who has been infected but has not yet shown signs of the disease Convalescent carrier: a person who is infected but no longer shows signs of acute disease Chronic carrier: infected with the agent with no sign of disease for a long period of time (for example, Typhoid Mary) Copyright ©2024 F.A. Davis Company  Mode of Transmission  The method through which the agent leaves its reservoir and enters its host Water, food, air, vectors, fomites, unprotected sexual contact, or penetrating trauma ‒ Vectors are usually insects that carry the disease from the reservoir to humans. ‒ Fomite is an inanimate object. Copyright ©2024 F.A. Davis Company  Host Characteristics  The human at risk for disease because of exposure to the agent  Susceptibility of the host: the likelihood of becoming infected with the agent Immunity Resistance Copyright ©2024 F.A. Davis Company  Host Characteristics: Immunity  Two types: innate and adaptive immune systems Innate immune systems are “first responders” with immune cell and chemicals. Adaptive immune systems are targeted to specific pathogens through creation of antibodies. ‒ Humoral immunity: production of antibodies via B cells ‒ Cellular immunity: destruction of pathogens with T cells Copyright ©2024 F.A. Davis Company  Host Characteristics: Immunity (continued)  Passive or active immunity Passive immunity: transferred from one individual to another Artificial passive immunity: involves the transfer of antibodies and can be done in various forms Active immunity: acquired through exposure to the agent Copyright ©2024 F.A. Davis Company  Host Characteristics: Defense Mechanisms  Avoidance Prevent exposure via anatomic or chemical barriers Example: body’s epithelial surfaces (i.e., skin)  Resistance Resists disease without antibodies Inherited or acquired  Tolerance Host’s responses that enhance tissues’ capacity to resist damage induced by pathogens Copyright ©2024 F.A. Davis Company  Host Characteristics: Colonization  Colonization Infected with agent but no sign of disease Can spread disease Example: Methicillin-resistant staphylococcus aureus (MRSA) Copyright ©2024 F.A. Davis Company  Breaking the Chain of Infection  The cycle of transmission for a specific pathogen provides needed information on the type of intervention that could break the chain of infection.  Interventions can be aimed at any point in the cycle of transmission. Copyright ©2024 F.A. Davis Company  Outbreak Investigation Steps  A systematic epidemiological investigation can Determine if there is a sudden increase in the incidence of a CD. Define what constitutes a case. Determine the severity of the outbreak, or case fatality rate (CFR). Map out the epidemic curve. Generate a hypothesis. Conduct case finding. Determine common sources of exposure. Identify the source of transmission or take action. Copyright ©2024 F.A. Davis Company  Life Cycle of the Agent Example: Life Cycle of the Hookworm Copyright ©2024 F.A. Davis Company  Case Fatality Rate and the Epidemic Curve  CFR Determines severity of the outbreak Represents number of fatal cases divided by the number of cases  Epidemic curve Plotted on graph Shows number of cases on the Y axis X axis placed by date Shows time elapsed from exposure to clinical symptoms Copyright ©2024 F.A. Davis Company  Epidemic Curve  Graph also helps determine if you have Point source ‒ Exposure at one point in time Intermittent source ‒ Exposure comes and goes Continuous source ‒ Exposure is ongoing Copyright ©2024 F.A. Davis Company  Sample Epidemic Curve Copyright ©2024 F.A. Davis Company  Managing an Outbreak  Management of epidemic Identify source Isolate source How best to break the cycle  Incubation period Exposure to onset of symptoms  Herd immunity Greater population protected (vaccine) Protects those who cannot be vaccinated or choose not to be Copyright ©2024 F.A. Davis Company  Managing an Outbreak (continued)  Requires prompt action on multiple levels Begins with a determination of how best to break the cycle of transmission ‒ Reservoir? ‒ Host?  Examples of public health interventions: Alerting the public to an ongoing risk to reduce further exposure Providing treatment to those exposed if warranted Copyright ©2024 F.A. Davis Company  Infectious Agents and Attack Rates  Disease is not necessarily immediately apparent following transmission of the pathogen.  The incubation period for the pathogen is the period of time between exposure and first signs of disease.  The infectious period is the period during which an infected person can transmit the infection to another susceptible host. Copyright ©2024 F.A. Davis Company  Herd Immunity  The immunity of a population to an agent Having a large enough portion of the population immune (by vaccine or past infection) prevents spread of the disease to persons in the population who do not have immunity.  The threshold of immunity This refers to the percentage of the population that must be immune to achieve herd immunity to a specific agent. Even if a few members of the community become infected, the population as a whole is protected from an outbreak. Copyright ©2024 F.A. Davis Company  Attack Rate and Secondary Attack Rate  Attack rate: the number of persons who are ill divided by the total population (ill + sick) Can be calculated based on a particular risk factor  Secondary attack rate: the total number of new cases among contacts divided by the total number of contacts Contacts: those in contact with persons who became ill following exposure to Copyright ©2024 F.A. Davis Company  Sexually Transmitted Infections (STIs)  Transmitted through sexual contact and exchange of bodily fluids  Preventable disease  More than 25 infectious agents  May cause serious illness and disability Reproductive health problems Fetal and perinatal health problems Cancer Copyright ©2024 F.A. Davis Company  Notifiable STIs in the United States  There are three notifiable STIs that have federally funded control programs: chlamydia, gonorrhea, and syphilis. Chlamydia and gonorrhea: associated with pelvic inflammatory disease (PID); can be passed on to the infant during delivery. Syphilis: four stages—primary, secondary, tertiary and latent; can be passed on to the infant during pregnancy or delivery. Copyright ©2024 F.A. Davis Company  STI Risk Factors  Main risk factor: unprotected sexual contact  Disparities based on Gender Ethnicity Sexual orientation Socioeconomic factors Underreporting of STIs in nonpublic health-care settings Access to care Copyright ©2024 F.A. Davis Company  HIV and AIDS  In 1981, a new STI grabbed the attention of the world—HIV.  Initially the Case Fatality Rate was high.  Now, because of successful treatments, the diagnosis of HIV infection is no longer a death sentence in the United States. At the end of 2019, 1.12 million people aged 13 and older were living with HIV infection in the United States. Copyright ©2024 F.A. Davis Company  HIV and AIDS (continued)  Can go 15 years after exposure before developing AIDS.  In the United States, 13% (158,500 people) are unaware they are infected.  25- to 29-year-olds have the highest rate of new cases. Men who have sex with men, black, and Hispanic/Latinx communities have the highest incidence.  Numbers are increasing among older adults. Copyright ©2024 F.A. Davis Company  UNAIDS 95-95-95  An ambitious treatment target to help end the AIDS epidemic by 2030  In 2020: 84% of all people living with HIV knew their HIV status. 73% of all people with diagnosed HIV infection were on sustained antiretroviral therapy. 66% of all persons in treatment were virally suppressed. Copyright ©2024 F.A. Davis Company  Controlling Communicable Diseases  Three main approaches: 1. Changing the environment ‒ Altering or eliminating the reservoir, controlling the vector, applying personal measures of hygiene, and using aseptic technique 2. Deactivating the agent ‒ Use of physical and chemical agents 3. Increasing host resistance ‒ Active or passive immunity ‒ Includes use of vaccine for training the immune system Copyright ©2024 F.A. Davis Company