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Questions and Answers
What characteristic feature gives the name to Poxviruses?
Which of the following statements about smallpox virus is true?
What was a major reason for the WHO's campaign to eradicate smallpox?
Where is the smallpox virus currently secured?
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What type of genome do Poxviruses possess?
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What is the primary health condition associated with the JC virus?
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Which of the following viruses is associated with Kaposi sarcoma?
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What structure characterizes the herpesvirus genome?
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What is the size range of hepadnaviruses?
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What type of nucleic acids do poxviruses contain?
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Which type of infections can hepadnaviruses cause?
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What is the composition of the vaccinia virus primarily made up of?
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In which cells do herpesviruses typically establish latent infections?
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Which virus family is characterized by non-enveloped, icosahedral, double-stranded linear DNA and is associated with pharyngitis?
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Which clinical symptom is primarily associated with Human Papilloma Virus (HPV)?
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What condition is caused by the BK virus and primarily affects transplant patients?
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Which of the following viruses is NOT a DNA virus family mentioned above?
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Which virus is known to cause chicken pox and can also reactivate to cause zoster?
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Which of the following is a clinical manifestation of Cytomegalovirus infection?
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What is the main structural characteristic of poxviruses compared to other families mentioned?
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What virus is associated with causing oral lesions and is primarily transmitted through sexual contact?
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What is one reason why smallpox is considered a significant threat for bioterrorism?
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Which clinical manifestation typically occurs after a 4 to 5 day incubation period of smallpox?
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What is the incubation period for the smallpox virus?
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What type of body inclusions are associated with the smallpox virus?
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How does the smallpox virus affect host immunity?
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What is a significant risk factor regarding the recognition of smallpox cases by healthcare providers?
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What is one consequence of the inflammatory responses caused by the smallpox virus?
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How long can scab forms of the smallpox virus remain stable at room temperature?
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What is the size range of adenoviruses?
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Which diseases can be caused by adenoviruses?
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What distinguishes parvoviruses from adenoviruses in terms of their genome?
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The replication of parvoviruses occurs in which type of cells?
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Which type of virus is known to cause erythema infectiosum?
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Which characteristic is NOT true about papillomaviruses?
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What size are polyomaviruses compared to other DNA viruses mentioned?
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What is a key difference between polyomaviruses and some other DNA viruses?
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What is the primary clinical manifestation associated with Epstein-Barr virus infection?
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Which DNA virus is known to be responsible for Fifth disease in children?
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Identify the virus associated with umbilicated warts.
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Which virus is characterized by its complex structure and is known to cause smallpox?
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Name the virus that causes progressive multifocal leukoencephalopathy.
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Study Notes
DNA-Containing Viruses Overview
- Major groups of clinically relevant DNA viruses include adenoviruses, parvoviruses, papillomaviruses, polyomaviruses, herpesviruses, hepadnaviruses, and poxviruses.
- Key symptoms and characteristics vary widely among these virus families.
Adenoviruses
- Medium-sized, nonenveloped viruses (70-90 nm) with icosahedral symmetry; genome is linear dsDNA (26-48 kb).
- Associated with acute respiratory diseases, conjunctivitis, and gastroenteritis.
- 67 known types infect humans, primarily targeting mucous membranes.
Parvoviruses
- Very small (18-26 nm), nonenveloped viruses with icosahedral symmetry, possessing ssDNA (~5 kb).
- Replicate in actively dividing cells; stable over pH range of 3-9.
- B19 virus causes Hydrops fetalis, aplastic anemia, and Fifth disease (erythema infectiosum).
Papillomaviruses
- Naked icosahedral viruses (55 nm) with double-stranded supercoiled DNA.
- Human Papillomavirus (HPV) can lead to genital cancers; associated with wart-like lesions.
- Animal-specific papillomaviruses do not infect humans.
Polyomaviruses
- Small (45 nm), nonenveloped, heat-stable viruses; structurally related to HPV.
- Notable human pathogens include JC virus linked to progressive multifocal leukoencephalopathy and BK virus causing nephropathy in transplant patients.
Herpesviruses
- Large viruses (150-200 nm) with a lipid-containing envelope and icosahedral nucleocapsid structure; linear dsDNA genome (120-240 kb).
- Cause lifelong latent infections; include HSV-1 (oral lesions), HSV-2 (genital herpes), and Varicella-Zoster virus (chickenpox and shingles).
- Epstein-Barr virus causes infectious mononucleosis, while HHV-8 is associated with Kaposi's sarcoma.
Hepadnaviruses
- Small (40-48 nm), enveloped viruses with partially dsDNA molecules (~3.2 kb).
- Known for causing acute and chronic hepatitis B infections; persistent infections increase liver cancer risks.
- Contains icosahedral nucleocapsid core within a lipid envelope.
Poxviruses
- Largest known viruses (220-450 nm) with complex structure; contain linear covalently closed dsDNA (130-375 kb).
- Pathogenic types include Smallpox, Molluscum contagiosum, and Monkeypox.
- Smallpox eradicated globally in 1980; stored in restricted laboratories.
Variola (Smallpox) Virus
- Two types: variola major (3-40% fatality) and variola minor (>1% fatality).
- Highly contagious, spread via respiratory droplets; no known animal reservoir.
- WHO-led eradication campaign in 1967 confirmed eradication by 1980; posing bioterrorism threat due to stability and high infectivity.
Smallpox Pathogenesis
- Entry through inhalation, initially infecting upper respiratory tract, followed by regional lymph nodes, leading to viremia and dissemination to organs.
- Incubation period lasts 12-14 days; clinical symptoms include fever and malaise before papulovesicular rash appears.
- Characteristic uniform vesicular rash forms, with lesions appearing simultaneously on face, arms, and extremities.
Diagnosis and Pathological Features
- Presence of eosinophilic inclusions (Guarnieri bodies) in infected cells.
- Viral proteins may impair host immune defenses, potentially leading to severe inflammatory responses.
- Diagnosis includes vesicular scrapings for analysis.
DNA-Containing Viruses Overview
- Major groups include adenoviruses, parvoviruses, papillomaviruses, herpesviruses, polyomaviruses, hepadnaviruses, and poxviruses.
- DNA viruses can be categorized based on envelope presence and capsid symmetry.
Clinically Important DNA Viruses
- Adenovirus: No envelope, icosahedral, ds linear DNA. Causes pharyngitis, conjunctivitis, and UTI.
- Parvovirus: No envelope, icosahedral, ss linear DNA. Associated with Fifth disease in children and anemia due to RBC destruction in fetuses.
- Papillomavirus: No envelope, icosahedral, ds circular DNA. Human Papilloma Virus (HPV) linked to warts and cervical/anal squamous cell carcinoma.
- Herpesvirus: Envelope present, icosahedral, ds linear DNA. Includes HSV-1 (oral lesions, cold sores), HSV-2 (genital herpes), Varicella-Zoster virus (chickenpox, shingles), Epstein-Barr virus (mononucleosis), and Cytomegalovirus (congenital abnormalities).
- Polyomavirus: No envelope, icosahedral, ds circular DNA. JC virus causes progressive multifocal leukoencephalopathy; BK virus affects transplant patients.
- Hepadnavirus: Envelope present, icosahedral, partially ds circular DNA. Hepatitis B virus leads to hepatitis.
- Poxvirus: Envelope present, complex structure, ds linear DNA. Includes smallpox (eradicated), molluscum contagiosum (umbilicated warts), and monkeypox (similar, less deadly).
Adenoviruses
- Medium-sized, nonenveloped, icosahedral viruses with fiber spikes enhancing host attachment.
- Pathogenic adenoviruses can cause vesicular skin lesions.
Poxviruses
- Genomes are linear, double-stranded DNA ranging from 130-375 kb.
- Poxvirus replication occurs in the cytoplasm, with numerous enzymatic proteins, including RNA polymerase.
Smallpox (Variola Virus)
- Consists of variola major (3-40% fatality) and variola minor (>1% fatality).
- Highly contagious via respiratory droplets; survives well in the environment.
- Global eradication confirmed by WHO in 1979; now stored in secure facilities.
Bioterrorism Concerns
- Smallpox is stable, high infectivity, and no longer widely vaccinated against, increasing population susceptibility.
- Response strategies are available through the CDC.
Smallpox Pathogenesis
- Virus enters via inhalation, replicates in the respiratory tract, and spreads through lymphatic dissemination.
- Incubation lasts 12 to 14 days, followed by fever and a characteristic papulovesicular rash developing into pustules.
- Guarnieri bodies are eosinophilic inclusions used for diagnosis.
Mpox (Monkeypox)
- Spreads through direct contact and has similar symptoms to smallpox, but lower fatality (1-10% depending on clade).
- Vaccine (JYNNEOS) developed for mpox and smallpox; requires 2 doses for effective protection.
Virus Replication Cycles of Major Virus Families
- Parvoviridae: No envelope, nucleus, 24 hours replication cycle.
- Polyomaviridae: No envelope, nucleus, 48 hours replication cycle.
- Adenoviridae: No envelope, nucleus, 25 hours replication cycle.
- Hepadnaviridae: Envelope present, nucleus/cytoplasm, 12-24 hours replication cycle.
- Herpesviridae: Envelope present, nucleus, 15-72 hours replication cycle.
- Poxviridae: Envelope present, cytoplasm, 20 hours replication cycle.
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Description
This quiz covers the major groups of clinically important DNA-containing viruses. Explore the characteristics of various virus families, their envelopes, and capsids. Enhance your understanding of microbiology and the mechanisms of host defense against these pathogens.
