Covid-19 and Emerging Infectious Disease Midterm Notes PDF

1 1 TISSUE RESPONSES TO INJURY AND INFECTION – COVID-19 and Emerging Infec5ous Disease 1. COVID-19 Cause: o COVID-19 is caused by SARS-CoV-2, a single-stranded RNA virus belonging to the...

1 1 TISSUE RESPONSES TO INJURY AND INFECTION – COVID-19 and Emerging Infec5ous Disease 1. COVID-19 Cause: o COVID-19 is caused by SARS-CoV-2, a single-stranded RNA virus belonging to the Coronavirus family. o The virus has a crown-like appearance due to spike (S) glycoproteins on its envelope, which are essenEal for binding to host cells. Pathophysiology: o Entry: The virus binds to the ACE2 receptor on host cells using the spike (S) protein, which is acEvated by the enzyme TMPRSS2. o Viral ReplicaIon: AJer entry, the virus releases its RNA genome, which is replicated using host cell machinery. New virions are assembled and released by exocytosis, infecEng more cells. o Immune Response: § Innate Immunity: SARS-CoV-2 delays the body's Type I interferon response, allowing it to replicate before detecEon. § Cytokine Storm: Excessive immune acEvaEon leads to a cytokine storm, characterized by elevated IL-6, IL-1, and TNF-α, causing severe inflammaEon and lung damage. § Lung Damage: The immune response leads to alveolar injury, edema, and acute respiratory distress syndrome (ARDS), which can be fatal. Transmission: o Person-to-person transmission occurs via respiratory droplets, direct contact, and contaminated surfaces. o The virus can also be transmiRed by touching the mouth, eyes, or nose aJer contacEng contaminated surfaces. Risk Factors: o Age and Gender: Older adults and males are more likely to develop severe disease. o ComorbidiIes: Obesity, diabetes, hypertension, cardiovascular disease, and chronic respiratory condiEons increase the risk of severe COVID-19. o Ethnicity: Certain ethnic groups have higher hospitalizaEon and mortality rates. o Immunosuppression: CondiEons that impair the immune response (like HIV or organ transplants) increase suscepEbility to severe disease. 2. Emerging InfecIous Diseases (EID) Emerging infecEous diseases are newly idenEfied or re-emerging diseases that have seen an increase in incidence or geographic range. Examples include Ebola, SARS, MERS, COVID-19, Zika virus, and Hantavirus. Cause:  2 o Most EIDs arise due to zoonoIc transmission, where pathogens spill over from animals to humans. o ZoonoIc hosts include bats, camels, civet cats, and other wildlife. For example: § SARS-CoV-1: Originated from civet cats in China. § MERS-CoV: TransmiRed from dromedary camels in Saudi Arabia. § COVID-19 (SARS-CoV-2): Linked to animal reservoirs, likely bats. Pathophysiology: o The pathophysiology varies by disease but oJen involves viral entry and replicaIon, host immune evasion, and cytokine-driven inflammaIon. o For example, Ebola's pathophysiology includes infecEon of dendriIc cells and macrophages, leading to immune evasion and cytokine storms. o SARS-CoV-2 pathophysiology involves viral entry via ACE2 receptors, immune acEvaEon, and ARDS, as seen in COVID-19. Transmission: o ZoonoIc Transmission: Spillover from animals to humans is a key feature of emerging infecEous diseases. For example: § MERS-CoV: From camels to humans. § SARS-CoV-1: From civet cats to humans. o Human-to-Human Transmission: AJer spillover, EIDs can be spread through direct contact, droplets, bodily fluids, and contaminated surfaces. o Airborne and Fomite Transmission: Respiratory diseases like COVID-19 and SARS are spread via respiratory droplets and contaminated surfaces. Risk Factors: o ZoonoIc Exposure: Close contact with wild animals or their habitats increases risk (e.g., Ebola from infected bats, gorillas, and chimpanzees). o Healthcare Workers: Frontline workers treaEng infected paEents (e.g., Ebola or COVID-19) are at risk of infecEon. o Travelers: People traveling to outbreak regions are at increased risk, especially for diseases like Ebola and Zika virus. o Climate Change and DeforestaIon: Habitat changes bring humans closer to wildlife reservoirs, increasing zoonoEc spillover risk. o GlobalizaIon and UrbanizaIon: Increasing human movement and dense populaEons facilitate transmission of EIDs. Summary Table CondiIon Cause Pathophysiology Transmission Risk Factors SARS-CoV-2 Binds to ACE2 receptors; Droplets, surfaces, Older adults, males, COVID-19 (RNA virus) cytokine storm, ARDS person-to-person diabetes, obesity Ebola virus Infects monocytes, DCs, Travelers, Contact with bodily Ebola (Filoviridae and macrophages; healthcare workers, fluids (blood, saliva) family) cytokine storm animal contact MERS-CoV Binds to DPP4 receptor; ZoonoEc (camels) & Animal contact, MERS-CoV (from camels) immune evasion respiratory droplets healthcare workers  3 CondiIon Cause Pathophysiology Transmission Risk Factors Respiratory SARS-CoV droplets, Travelers, SARS-CoV (from civet Binds to ACE2 receptors contaminated healthcare workers cats) surfaces Hantavirus Infects pulmonary InhalaEon of rodent Exposure to rodent- Hantavirus (from rodents) endothelial cells urine/feces contaminated areas Zika virus Infects neural progenitor Mosquito bites Tropical regions, Zika Virus (Flavivirus cells, leading to (Aedes mosquitoes) pregnancy family) microcephaly