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Questions and Answers
Which virus is primarily associated with the respiratory system and can lead to severe pneumonia?
What type of virus is Norovirus primarily classified as?
Which of the following viruses is linked to both cervical cancer and genital warts?
Which virus can cause viral conjunctivitis?
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Which of the following viruses does NOT primarily target the nervous system?
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What is the primary clinical condition caused by Hepatitis viruses?
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Which virus is associated with myocarditis and pericarditis?
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Which form of the Herpes Simplex Virus primarily causes genital herpes?
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What is the primary mode of transmission for SARS-CoV-2?
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What is a common treatment approach for MERS-CoV?
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Which statement accurately describes the mortality rate of MERS-CoV?
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What preventive measure is recommended for MERS-CoV?
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Which of these symptoms is commonly associated with COVID-19?
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What is the first identified location of SARS-CoV-2?
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What diagnostic method is used for both COVID-19 and MERS-CoV?
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Which therapy is commonly used for severe cases of COVID-19?
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Which virus primarily targets the immune system?
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What is the primary mode of transmission for respiratory viruses?
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What is the function of neuraminidase (NA) in the influenza virus?
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Which of the following diseases can be caused by arboviruses?
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What characteristic is common to respiratory viruses?
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Which surface protein on influenza viruses is critical for binding to host cells?
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What is an example of a systemic infection caused by Cytomegalovirus (CMV) in immunocompromised patients?
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What is the significance of classifying different strains of influenza A, such as H1N1 and H3N2?
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Which type of influenza is known for causing pandemics?
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What is the primary mode of transmission for the influenza virus?
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Which diagnostic test is considered the gold standard for detecting influenza?
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When should antiviral medications be administered for maximum efficacy?
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What is a common complication associated with influenza?
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Which antiviral medication is most commonly used to treat influenza?
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For whom is annual influenza vaccination particularly recommended?
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What significant information has PCR technology revealed about the 1918 influenza virus?
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What is the main diagnostic assay used for adenovirus infections?
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Which of the following is the most sensitive test for identifying adenovirus infection?
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What is the primary genomic characteristic of paramyxoviruses?
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Which virus is recognized as a leading cause of bronchiolitis and pneumonia in infants?
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What method is suggested for preventing adenovirus infections?
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Which of the following is a characteristic of measles virus?
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What is one way to minimize the risk of waterborne outbreaks of conjunctivitis?
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What is a common disease caused by the parainfluenza virus?
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Study Notes
Introduction to Viruses of Clinical Significance
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Studying viruses by categorizing them according to the organ system they affect is a practical approach to understanding the clinical impact of viruses and the diseases they cause.
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This method makes it easier to correlate the viral pathogens with their symptoms, diagnostic methods, treatments, and preventive measures.
Respiratory Viruses
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Respiratory viruses primarily affect the respiratory tract, causing illnesses ranging from the common cold to severe pneumonia.
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Respiratory viruses are crucial in managing respiratory outbreaks and pandemics.
Gastrointestinal Viruses
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Gastrointestinal viruses primarily infect the digestive system, leading to gastroenteritis, diarrhea or hepatitis.
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Common examples of gastrointestinal viruses include Norovirus and Rotavirus.
Nervous System Viruses
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Nervous system viruses target the central and peripheral nervous systems, causing neurological diseases like encephalitis or meningitis.
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Examples include Rabies virus, Poliovirus, and Herpes Simplex Virus.
Dermatological Viruses
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Dermatological viruses manifest through skin lesions or rashes.
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Examples include Human Papillomavirus (HPV), Varicella-Zoster virus (VZV), and Molluscum contagiosum.
Hepatic Viruses
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Hepatic viruses primarily affect the liver, leading to conditions such as hepatitis.
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Examples include Hepatitis A, B, C, D, and E viruses.
Cardiovascular System Viruses
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Coxsackie B Virus is associated with myocarditis and pericarditis.
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Enteroviruses can cause viral myocarditis, leading to heart inflammation and damage.
Reproductive System Viruses
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Human Papillomavirus (HPV) is linked to cervical, anal, and genital cancers, as well as genital warts.
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Herpes Simplex Virus (HSV-2) causes genital herpes.
Ocular Viruses
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Adenovirus can cause viral conjunctivitis (pink eye).
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Herpes Simplex Virus can lead to ocular herpes, causing keratitis or more severe eye infections.
Systemic Viruses
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HIV affects multiple systems but primarily targets the immune system.
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Cytomegalovirus (CMV) can cause systemic infections in immunocompromised patients, affecting the liver, lungs, brain, and gastrointestinal tract.
Arthropod-borne Viruses (Arboviruses)
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Arboviruses are viruses transmitted by arthropods such as mosquitos, ticks, and sandflies.
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Arboviruses typically affect multiple organ systems, depending on the virus, but are often categorized based on their primary clinical manifestations.
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Arboviruses can cause a range of diseases, including febrile illness, encephalitis, hemorrhagic fever, and joint/muscle pain.
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Examples of arboviruses include Dengue and Zika.
Influenza Virus (Orthomyxoviridae)
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Influenza A, B, and C are the only members of the family Orthomyxoviridae.
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Influenza A and B viruses are the most clinically significant.
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Orthomyxovirus virions contain a segmented RNA genome (sdRNA) and have a helical- shaped virion with an envelope.
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Orthomyxoviruses have hemagglutinin (HA) and neuraminidase (NA) on their surface.
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The influenza viruses, A, B, and C, are the only members of the family Orthomyxoviridae.
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Hemagglutinin (HA):
- A glycoprotein on the surface of the influenza virus that allows the virus to bind to and enter host cells by attaching to sialic acid receptors on the cell surface.
- It is crucial for the virus’s ability to infect host cells.
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Neuraminidase (NA)
- Another surface protein that helps the virus to release from the infected host cell after replication.
- It cleaves sialic acid, allowing the virus to spread to other cells.
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These proteins are the basis for classifying different strains of influenza A virus, such as H1N1 (swine flu, 2009 pandemic, 1918 Spanish flu) or H3N2 (seasonal flu), where the numbers correspond to specific subtypes of HA and NA proteins.
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Influenza A: The most virulent and known for causing pandemics (e.g., H1N1, H3N2)
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Influenza B: Causes seasonal epidemics but is generally less severe than type A.
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Influenza C: Causes mild respiratory illness.
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Mode of Transmission: Airborne via respiratory droplets from coughs and sneezes and direct contact by touching surfaces contaminated with the virus.
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Diseases: Causes influenza (trangkaso), characterized by symptoms such as fever, chills, cough, sore throat, body aches, and fatigue.
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Complications: Can lead to pneumonia, bronchitis, sinus infections, and worsening of chronic health conditions.
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Clinical Significance: Influenza has seasonal epidemics with significant morbidity and mortality, particularly among the elderly, young children, and those with chronic health issues. Vaccination is critical for prevention.
Influenza Virus (Orthomyxoviridae) Laboratory Diagnosis
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Rapid influenza diagnostic tests (RIDTs): Detects viral antigens, provides results in about 15 minutes but can be less sensitive.
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RT-PCR: Gold standard, highly sensitive, detects and differentiates between influenza types and subtypes.
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Viral culture: Less commonly used but can be done for confirmation.
Influenza Virus (Orthomyxoviridae) Treatment
- Antiviral medications:
- Oseltamivir (Tamiflu): Most common antiviral for influenza.
- Zanamivir (Relenza) and Peramivir are alternatives.
- Should be administered within 48 hours of symptom onset for maximum efficacy.
Influenza Virus (Orthomyxoviridae) Prevention
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Annual influenza vaccination: Recommended for everyone, particularly vulnerable groups (children, elderly, healthcare workers).
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Hand hygiene and respiratory etiquette
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Isolation of infected individuals during outbreaks.
Reconstruction of 1918 Influenza Virus
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PCR technology has yielded gene fragments of influenza virus from archival lung tissue specimens from victims of the 1918 Spanish flu epidemic.
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The complete coding sequences of all eight viral RNA segments have been determined, and the sequences document that it was an H1N1 influenza A virus.
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It appears that the 1918 virus was not a reassortant (not a combination of the RNA segments) but was derived entirely from an avian source that adapted to humans.
Adenoviruses
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Most commonly cause respiratory tract infections, but can also cause conjunctivitis, gastroenteritis, and other diseases.
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Symptoms: Fever, sore throat, cough, runny nose, and sometimes conjunctivitis.
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Diagnosis:
- Polymerase chain reaction (PCR) assays are routinely used for diagnosis of adenovirus infections in respiratory samples, blood, tissues, or body fluids, usually by using primers from a conserved viral sequence (eg, hexon and VA I) that can detect all serotypes.
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Serology: - The complement-fixation test is an easily applied method for detecting infection by any member of the adenovirus group but the test has low sensitivity. - If specific identification of a patient’s serologic response is required, antibody neutralization or hemagglutination inhibition tests can be used. - The neutralization test is the most sensitive
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Treatment: There is no specific treatment for adenovirus infections.
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Prevention: - Careful hand washing is the easiest way to prevent infections. - Environmental surfaces can be disinfected with sodium hypochlorite. - In group settings, paper towels may be advisable because dirty towels can be a source of infection in outbreaks.
- The risk of waterborne outbreaks of conjunctivitis can be minimized by chlorination of swimming pools and waste water. - Strict asepsis during eye examinations, coupled with adequate sterilization of equipment, is essential for the control of epidemic keratoconjunctivitis.
Paramyxo Viruses (Paramyxoviridae)
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Genome: Non-segmented, negative-sense single-stranded RNA (ssRNA).
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Shape: Enveloped, pleomorphic (can have various shapes, typically spherical or filamentous).
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Replication: Occurs in the cytoplasm of the host cell.
Key Paramyxo Viruses
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Respiratory Syncytial Virus (RSV): A leading cause of bronchiolitis and pneumonia in infants and the elderly.
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Parainfluenza Virus: Causes croup (laryngotracheobronchitis), especially in children, as well as bronchiolitis and pneumonia.
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Measles Virus: Causes measles, a highly contagious viral disease characterized by fever, cough, and a widespread rash.
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Mumps Virus: Causes mumps, characterized by fever and swelling of the salivary glands.
Paramyxo Viruses (Paramyxoviridae) Diseases:
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Paramyxoviruses cause a range of respiratory illnesses, from the common cold to severe diseases such as bronchiolitis, pneumonia, and croup in children.
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Measles and mumps are also notable systemic diseases caused by paramyxoviruses.
MERS-CoV (Middle East Respiratory Syndrome Coronavirus)
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First Identified: 2012 in Saudi Arabia.
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Outbreaks: Primarily in the Middle East but also seen in other countries through travel.
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Transmission: Zoonotic transmission from camels to humans; limited human-to-human spread, mostly in healthcare settings.
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Symptoms: Fever, cough, shortness of breath, and gastrointestinal symptoms; can progress to pneumonia and kidney failure.
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Mortality Rate: ~34%.
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Diagnosis: RT-PCR, serology, viral culture.
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Treatment: Supportive care; investigational antivirals in some cases.
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Prevention: Avoiding contact with camels, infection control in healthcare settings, and travel precautions.
SARS-CoV-2 (COVID-19)
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First Identified: December 2019 in Wuhan, China.
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Pandemic: Global pandemic 2020.
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Transmission: Primarily through respiratory droplets, aerosols, and close contact; also via contaminated surfaces.
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Symptoms: Wide range, from asymptomatic to severe pneumonia; common symptoms include fever, cough, loss of taste/smell, and fatigue. Severe cases may involve ARDS, multi-organ failure, and death.
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Mortality Rate: Varies by region and healthcare capacity; generally lower than MERS but highly infectious.
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Diagnosis: RT-PCR, antigen tests, serology for past infections.
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Treatment: Antivirals (e.g., remdesivir), monoclonal antibodies, corticosteroids (e.g., dexamethasone), oxygen therapy, and mechanical ventilation in severe cases.
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Prevention: Vaccination (Pfizer, Moderna, AstraZeneca, Janssen, Sinovac), masks, physical distancing, hand hygiene, and travel restrictions.
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