Viral Infections Affecting the Skin and Joints Flashcards
(32 cards)
what are the components of sebum and sweat?
sebum: low pH, high lipid
sweat: low pH, high salt, lysozymes and RNase
what are the two viruses that cause maculo-papular rashes?
Measles Virus
Rubella Virus
What is the Measles virus (MeV) and its genetic structure?
- Measles is caused by the Measles virus (MeV), which is a negative-sense RNA virus with a 16kb genome and a lipid envelope
- It belongs to the Morbillivirus genus of the Paramyxoviridae family
What are the structural proteins of the Measles virus (MeV)?
The measles virion has 6 proteins:
- 2 surface glycoproteins: Hemagglutinin (H) and Fusion (F)
- Matrix (M) protein
- Nucleocapsid (N) protein: surrounds the negative-sense RNA
- 2 replicase proteins: Phosphoprotein (P) and Large polymerase protein (L)
How does the Measles Virus spread from person to person and inside the body?
- spreads through aerosol droplets, initial infection starts in the oropharynx and spreads to the lymph nodes of the neck then to the whole body
What are the symptoms of Measles Virus?
- cold and fever
- macular rash with raised spots
- rash begins on face then spreads to trunk and extremities
- Koplik’s spots in oral mucosa
how does the Measles rash occur?
the immune attack against infected epithelial cells where CD4+ and CD8+ T lymphocytes are heavily involved in the response, contributing to the mononuclear cell accumulation seen in biopsies
Why is measles still a major global health concern?
- Measles is the leading cause of vaccine-preventable death among children
- Despite the availability of the MMR vaccine, millions remain at risk
- In developed countries, the death rate is 1-5%, but in malnourished children, it can reach 10-30%
- Over 500,000 children die each year due to measles-related complications like pneumonia, diarrhea, encephalitis, and corneal scarring
- Failure to deliver at least one dose of the vaccine to all infants is the primary reason for ongoing high death rates
What is German Measles and what is its genetic structure?
also called Rubella, a mild, self-limiting viral infection caused by the Rubella virus (togavirus) that is enveloped and has a single stranded RNA genome
How does German Measles spread?
spread through aerosol droplets that is typically not severe, but it becomes very serious if contracted by a pregnant woman during the first trimester
What is Congenital Rubella Syndrome (CRS) and its impact?
- rubella virus infects the fetus during pregnancy, causing systemic inflammation and disrupting CNS and organ development
- can lead to small birth weight, blindness, hearing loss, mental retardation, and heart problems
- infection can last for months to years in newborns
- MMR vaccine is highly effective in preventing rubella
How is Arthritis associated with Rubella Virus infection?
Natural Infection:
- arthritis begins suddenly, about 1 week before or after the rash
- symptoms include morning stiffness and pain in multiple joints (fingers, knees, wrists)
- usually lasts a few days to weeks
Vaccination-related Arthritis:
- after rubella vaccination, especially with the HPV77/DK12 strain
- RA27/3 strain, currently used in the US, causes joint symptoms in about 15% of recipients
what are the viruses that cause vesicular and pustular rashes?
- HSV 1 and 2: cold sores
- VZV, Human Herpesvirus-3: chicken pox
- Human Pox Virus: smallpox
What are the key features and structure of the Herpes Simplex Virus (HSV)?
HSV consists of two main types:
- HSV-1 and HSV-2
- Both types are highly contagious and widespread
- virus has a double-stranded DNA (dsDNA) core, surrounded by a protein capsid, an icosahedral symmetry, a tegument layer, and is enclosed by an envelope
How do HSV-1 and HSV-2 differ in their infection sites?
- HSV-1: Mainly causes oral herpes (cold sores) but can also infect the genitals
- HSV-2: Mainly causes genital lesions but can also infect the mouth
what are cold sores/ fever blisters?
- vesicles on the lips caused by HSV-1 or HSV-2
- can remain latent in trigeminal nerve ganglia
- rare complication: herpes encephalitis
- acyclovir can lessen symptoms
what is herpetic whitlow?
- painful infection of the fingers or thumb caused by auto-inoculation of HSV from another infected site
- common in toddlers and healthcare workers exposed to infected secretions
what is Eczema Herpeticum?
A severe, widespread cutaneous herpes infection that occurs in patients with atopic eczema or other skin disorders when HSV infects areas of broken skin, leading to widespread vesicular eruptions
What virus causes chickenpox and shingles?
Varicella-Zoster Virus (VZV), a human alpha herpesvirus, causes varicella (chickenpox) and zoster (shingles).
How does Varicella-Zoster Virus (VZV) spread and establish latency?
- infects mucosal epithelial cells, then spreads to tonsils and lymphoid tissues, infects T cells, and reaches cutaneous sites
-establishes latency in sensory ganglia (dorsal root ganglion) where it can reactivate later
What happens during the reactivation of Varicella-Zoster Virus (VZV)?
Reactivation occurs when cell-mediated immunity declines, especially in elderly, AIDS patients, or immunocompromised individuals, causing shingles (herpes zoster).
What are the clinical features of chickenpox (varicella)?
- Common virus, now less prevalent due to vaccines
- Usually benign with lifelong immunity
- Can be life-threatening in immunocompromised individuals
- Recovery results in lifelong VZV latency
- May re-emerge as shingles (zoster) later in life
What vaccines are available for Varicella-Zoster Virus (VZV) prevention?
- Zostavax™ – Live attenuated vaccine
- Shingrix™ – Subunit vaccine, more effective for older adults
What is the typical age-related risk for shingles reactivation?
risk of herpes zoster increases significantly after 50 years of age, with the highest incidence in individuals over 60.
