Immunology_chapter_13_parts_4-9

Chapter 13: Part Four - COVID-19 and Related Viruses

Overview of COVID-19

• COVID-19, also known as SARS-CoV-2, is the third coronavirus identified in humans.

• Other coronaviruses: SARS-CoV-1 (2002 outbreak in China) and MERS (2014 outbreak in Saudi Arabia).

• Originates primarily from animals, including bats.

Transmission of COVID-19

• Average transmission rate: 2 - 2.5 people per infected individual.

• Asymptomatic carriers contribute significantly to spread.

• Viral shedding can occur before symptoms appear, potentially up to 2-4 weeks, through respiratory secretions and urine.

High-Risk Populations

• Immunocompromised individuals and those with underlying medical conditions (e.g., cancer, diabetes, obesity) are at greater risk for severe outcomes.

• Common conditions that increase risk include: COPD, cardiac issues, chronic kidney disease, and sickle cell disease.

Symptoms and Onset

• Symptoms typically manifest 2-14 days after exposure, ranging from mild to severe illness.

  • Common symptoms: fever, cough, shortness of breath.

  • Long COVID symptoms: chronic pain, shortness of breath, intense fatigue, brain fog, and chest pain.

Immunologic Response to COVID-19

• Cytokines: Increased interleukin-1 beta and tumor necrosis factor-alpha observed in infected individuals.

• Key immune cells involved include neutrophils, monocytes, macrophages, and NK cells.

• Platelet Changes: Increased platelets in mild cases and decreased platelets with severe infections, including giant platelets observed.

Diagnostic Laboratory Evaluation

• Common lab findings:

  • Hematology: increased WBC counts, neutrophilia, lymphopenia, and elevated D-dimer and CRP.

  • Chemistry: increased LDH, ALT, AST, and bilirubin levels.

• D-dimer indicates potential clotting issues, often seen in COVID-19 patients.

Severe Clinical Complications

• Cytokine Storm Syndrome: Uncontrolled inflammatory response leading to ARDS and potentially fatal complications.

• Disseminated Intravascular Coagulation (DIC): Associated with hypercoagulability, causing cycles of clotting and breakdown.

Laboratory Testing for COVID-19

• Types of testing:

  • Diagnostic testing for symptomatic individuals.

  • Screening for asymptomatic individuals.

  • Surveillance for infection rates in populations.

• NAT: Molecular tests (PCR) to detect viral nucleic acid.

• Serological tests: Determining prior infection via antibody detection (IgM/IgG).

Treatment and Prevention

• Convalescent Plasma: High in antibodies, primarily used for high-risk patients.

• Ongoing development of monoclonal antibodies, interferon, steroids, and antiviral therapies (e.g., remdesivir).

Chapter 13: Part Five - Dengue Fever

Overview of Dengue Fever

• A single-stranded RNA virus with four serotypes (Dengue virus types 1-4).

• Belongs to the Flaviviridae family.

• Approximately 50 million infections globally each year, endemic in tropical regions such as India and Southeast Asia.

• High-risk areas in the U.S.: Texas and Florida.

Transmission

• Transmitted primarily by Aedes aegypti mosquitoes.

Symptoms

• Often asymptomatic or range from mild to severe (even fatal).

  • Common symptoms: fever, headache, ocular pain, joint and muscle pain, rash, nausea, vomiting.

• Severe cases lead to hemorrhagic fever with significant bleeding.

Diagnostic Tests

• Molecular Assay: Reverse transcriptase PCR.

• Serological Testing: ELISA also available.

Chapter 13: Part Six - TORCH Panel

Overview

• TORCH: Acronym for infections harmful to the fetus in pregnant women.

  • T: Toxoplasma gondii (or Treponema pallidum).

  • O: Other viruses.

  • R: Rubella.

  • C: Cytomegalovirus (CMV).

  • H: Herpes simplex virus (HSV).

Significance

• Tests for infections that may affect the fetus, even if the mother is asymptomatic.

• IgM antibodies are significant for newborns; IgG can cross the placenta from mother to fetus.

Specific Infections

• Toxoplasmosis: Caused by Toxoplasma gondii; cats as definitive hosts. Increasing rise of infection in different regions.

• Congenital Toxoplasmosis: Can result in severe fetal complications including CNS malformations.

• Rubella: Causes serious birth defects, especially in the first trimester.

• Cytomegalovirus (CMV): Most common viral transmission to fetuses and can result in congenital infections.

Chapter 13: Summary of Laboratory Evaluation and Diagnostic Tests

Laboratory Tests

• Tests used to confirm infections, distinguish between acute and convalescent phases, and monitor immune responses.

• IgM and IgG test interpretation helps determine immunity and infection status.

Conclusion

• Understanding these viral infections is critical for managing health risks among pregnant women and immunocompromised individuals.