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COMMUNICABLE DISEASE Week 6 Nur631 Public Health Nursing and Epidemiology objectives • review the chain of transmission in infectious/ communicable disease. • discuss the causation of emerging and re-emerging infectious / communicable disease. • describe the role and function of the nurse in the control of communicable disease. • knowledge and use of the reporting system for notifiable diseases. • explain the ethic –legal issues that the nurse will encounter when caring for client’s suffering from and infectious/ communicable disease. epidemiologic triad The Triangle has three corners (called vertices): • Agent, or microbe that causes the disease (the “what” of the Triangle) • Host, or organism harbouring the disease (the “who” of the Triangle) • Environment, or those external factors that cause or allow disease transmission (the "where” of the Triangle) epidemiologic triad The mission of an epidemiologist is to break at least one of the side of the Triangle. The Agent—“What” • The agent is the cause of the disease. • Disease-causing microbes are bacteria, virus, fungi, and protozo a (a type of parasite). They are what most people call “germs.” The Host—“Who” • Hosts are organisms, usually humans or animals, which are exposed to and harbor a disease. • The host can be the organism that gets sick, as well as any animal carrier (including insects and worms) that may or may not get sick. • Different people may have different reactions to the same agent The Environment—“Where” • The environment is the favourable surroundings and conditions external to the host that cause or allow the disease to be transmitted. Characteristics of infectious disease agents • Pathogenicity: refers to the capacity of the agent to cause disease in infected host. • Virulence: refers to the severity of the disease.(i.e. , whether sever e clinical manifestations are produced. • e.g. The Rabies virus, which almost always produces fatal disease in humans. • Resistance: refers to the ability of the agent to survive adverse env ironmental conditions. • Infectivity: refers to the capacity of the agent to enter and multiply in a susceptible host and thus produce infection or disease. • e.g. Polio and measles are diseases of high infectivity. Chain of Infection • Disease transmission occurs when the agent leaves its reservoir or host through a portal of exit, is conveyed by some mode of transmission, and enters through an appropriate portal of entry to infect a susceptible host. Chain of Infection Reservoir • The reservoir of an infectious agent is the habitat in wh ich the agent normally lives, grows, and multiplies. • Reservoirs include humans, animals, and the environment. • Microorganisms can thrive in human beings, animals and inanimate objects such as water, table tops and door knobs. Reservoir Human reservoirs e.g. sexually transmitted diseases, measles, mumps, streptococcal infection, and many respiratory pathogens • Carrier is a person with inapparent infection who is capable of transmitting the pathogen to others. • Incubatory carriers are those who can transmit the agent during the incubation period before clinical illne ss begins Reservoir • Convalescent carriers are those who have recovered from their illness but remain capable of transmitting to others. • Chronic carriers are those who continue to harbor a pathogen such as hepatitis B virus or Salmonella Typhi the causative agent of typhoid fever, for months or even years after their initial infection. Portal of exit • It is a place of exit providing a way for a microorganism to leave the reservoir. • Principal portals of exit are: Digestive system, urinary system, respiratory system, reproductive system and the blood. Modes of transmission Direct: • Direct and immediate transfer of infectious agents to a receptive portal of entry through which human or animal infection may take place. • e.g. touching, biting, kissing or sexual intercourse, or by direct droplet spray onto the mucous or conjunctiva membranes of the eye, nose, or mouth du ring sneezing, coughing, spitting, singing, or talking (usually at a distance of 1 meter or less). Modes of transmission Indirect: Vehicle-borne – Vehicle (Transmission)- any mechanism by which a susceptible host is exposed to an infectious agent. Contaminated inanimate materials or objects (fomites) such as toys, handkerchiefs, soiled clothes, bedding, cooking or eating utensils, surgical instruments or dressings; water, food, milk, biological products including blood Modes of transmission Vector-borne: Spread by animals, most often arthropods. Vector-borne diseases include those spread by ticks and mosquitoes. Airborne: Spread through the air. An organism spread in this way can be suspended in air. It is similar to a droplet spread organism because an infected person can spread i t by coughing, sneezing or talking, and an uninfected pers on can become infected by inhaling the organism Modes of transmission Natural History of Disease Timeline Modes of transmission Iceberg Concept of Infection The iceberg concept of infection posits that the tip of the iceberg, which corresponds to active clinical disease. Any Questions? Vectors Vectors are transmitters of disease causing organisms known as pathogens. They carry pathogens from one host to another Chikungunya • Chikungunya (also known as ChikV) is a virus infection that can cause a devastating illness. • It is transmitted to people by Aedes aegypti and Aedes albopi ctus mosquitoes, the same mosquitoes that transmit Dengue. • Aedes aegypti is a household container breeder, an aggressive daytime biter attracted to humans, and it is the primary vecto r of the Chikungunya virus. Chikungunya Chikungunya Signs and Symptom Principal symptoms are most often characterized by •Fever, •Headache, •Fatigue, •Nausea, and vomiting •Muscle pain, •Rash •Joint pain - often in the hands and feet. There is no vaccine or specific antiviral treatment currently available for Chikungunya fever, but there are medications that can help reduce the fever and pain. Zika Virus • Zika virus is an emerging disease in the United States. • It was first identified in 1947 in Uganda. • The first large outbreak of disease caused by Zika virus infecti on was reported from the Island of Yap in 2007. • These mosquitoes are aggressive daytime biters but can also bite at night. • Currently, there is no vaccine or medicine for Zika virus, but re searchers are currently working on efforts to address this. Zika Virus Transmission • The transmission of Zika virus to humans can occur in several different ways. • The primary route of transmission is through the bite of an infected mosquito. • pregnant woman is infected, she can pass Zika virus to her fetus during pregnancy or around the time of birth. • Zika virus can also be passed through sex from an infected person to his or her partners, • Another probable route of transmission for Zika virus is through blood transfusions. Zika Virus Vectors are transmitters of disease causing organisms known as pathogens. They carry pathogens from one host to another Zika Virus Many people infected with Zika virus will have no symptoms or will have only mild symptoms. symptoms of Zika virus, the most common ones include: • Fever • Rash • Joint pain • Conjunctivitis (red eyes) • Headache • Muscle pain Zika Virus Emerging infectious disease • Newly identified & previously unknown infectious agents that cause public health problems either locally or internationally Re-emerging infectious disease • Infectious agents that have been known for some time, had fallen to such low levels that they were no longer considered public health problems & are now showing upward trends in incidence or prevalence worldwide Factors Contributing To Emergence • Evolution of pathogenic infectious agents (microbial adaptation & change) • Development of resistance to drugs • Resistance of vectors to pesticides • Human demographic change (inhabiting new areas) • Human behavior (sexual & drug use) • Human susceptibility to infection (Immunosuppression) • Poverty & social inequality • Climate & changing ecosystems • International travel & commerce • Deterioration in surveillance systems