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Chapter 9Global Infectious Diseases- Few developed countries think of infectious diseases as a major problem- Many parts of the world they still are- Everyone should be concerned about infectious diseases because they have potential to affect everyone Parasites- Parasites: eukaryotic organisms that survive off a living host- Some parasites only minimally affect their hosts, but others can cause serious illness or disability- Protozoa: single celled organisms that have animal like characteristics and often live in watero Classified by how they move and characteristics of lifestyle- Helminthes are endoparasitic worms that live inside the body of the hosto Classified by shape and lifestyleo Acquired by walking barefoot in contaminated soil, wading in contaminated water, ingesting contaminated good or water and by being bit by worm infested insects- Ectoparasitic: animals that live on the exterior surface- Antiparasitic medications will kill many parasites- But some are becoming drug resistantFungi- Fungi: come in many forms including molds and yeasts- Important decomposers- Fungal conditions frequently occur after bacteria that normally live in the body are disturbed by antibiotic use or immunosuppression- Live in moist dark placesPrions- Prions: pertinacious infections particles- Cause rare degenerative nervous system diseases called transmissible spongiform encephalopathy (TSEs)- No treatment so prevention is essentialExposure, infection, and disease- Natural history: describes usual timeline from exposure to particular agent to infection to either recovery or death- Not all exposures cause infections- Some people are more vulnerable and immune system is weakened by age, malnutrition, cancer treatments, immunosuppressive drugs, or existing infections with other pathogens- Infectivity: capacity of an infectious agent to cause infection in a susceptible humano Measured by calculating secondary attack rate: average number of other people that one contagious person affects- Infection: occurs when infectious agent begins to reproduce inside a person- Latent phase/ incubation period: immediately after infections, infectious agents multiplies in the host but the infected individual does not feel sick- Detection in early stage can be critical- Disease: occurs when infected person develops symptoms or illness – not call infections cause disease- Pathogenicity: capacity of an infectious agent to cause disease in an infected human, andmeasured by the proportion of individuals with laboratory confirmed infection who become ill- Those who develop symptomatic disease there are three possible outcomes: death, recovery within immunity, recovery without immunity- Most infections the recovery rate is high- Virulence: ability of an infectious agent to cause disease or death in a host and is measured by the proportion of severe or fatal cases among all people who have the disease- Virulent infections will have high case fatality- Some infections are acute (short term)- Others are chronic (long term)- Chronic infections can increase susceptibility to other infections and some chronic infections increase risk of cancer- Infections spark an immune process that forms ‘memory’ antibodies in the blood that allow the body to quickly destroy nay new pathogens of the same type to invade the bodyin the futureInfectious Disease Transmission- Many modes of transmission- Direct transmission is person to person transmission when susceptible person touches an infectious person’s blood, or other bodily fluids, then touches his or her moth, eyes, nose or other portal of entry- Frequent hand washing and use of protective equipment can help prevent transmission- Airborne transmission occurs when pathogens are aerosolized or suspended in the air andpeople breathe in that contaminated air- May need to treat person in isolation- Vector borne infections are spread by vector insects- Can be partially attained through the use of insecticides- Animals can play a role in the infection transmission process- Fecal oral transmission: occurs when person ingests products contaminated with fecal material from animals or humans- Indirect transmission can occur as a result of contact with inanimate objects called fomites- Vertical transmission/ mother to child transmission: could be passed to fetus during pregnancy, delivery to baby or through breast milk- To control infectious diseases several other aspects must be considered- Reservoir: environment home for infectious agent- Antroponoses: infectious diseases that usually only happen in humans- Zoonoses: infectious diseases that usually occur in animals and only occasionally affect humans- Cycle of infection: how infectious agent cycles between different species- Each host in the cycle of infection must be considered for inclusion in an infection control planDiarrheal and foodborne diseases- Infectious diseases – illnesses cause by communicable pathogens- are often classified based on primarily symptoms they cause, the mode of transmission, or by other key features- Most diarrheal infections and other forms of infectious gastroenteritis are spread by fecal oral transmission- Cholera infection causes severe watery diarrhea- Typhoid, paratyphoid, shigellosis, salmonellosis, and campylobacteriosis are also bacterial infectious diarrheal diseases- Protozoan infections can also be spread through food and water that has been contaminated by animal feces- Viruses are even more common as a cause of diarrhea- Most diarrheal infections are short term but some can be chronic- Effective methods for prevention of diarrhea include safe food handling, frequent hand washing, consistent access to clean drinking water, and community wide sanitationRespiratory diseases- Upper respiratory infections like cold and lower respiratory infections like pneumonia areoften caused by viruses- Most respiratory infections are acquired through air- Prevention methods for respiratory infections include isolating infected persons, reducingexposure to smoke, vaccinating members of vulnerable population groups, and encouraging frequent hand washing and the covering of the nose and mouth when coughing or sneezing Vectorborne diseases- Several types of bacterial and rickettsial infections are spread by the bites of infected ticks and fleas- Viruses spread by anthropods such as insects and arachnids are called arboviruses- Vectorborne protozoan infections are of particular global health concern- African


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UMD FMSC 280 - Global Infectious Diseases

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