12_STDs caused by Viruses Flashcards
STD: define
- sexually transmitted diseases (aka STIs and Venereal disease)
- illnesses that ahve a significant probability of transmission b/w humans through sexual behavior, incl:
- vaginal intercourse
- anal sex
- oral sex
- ~20M new cases of STIs every year
other ways STIs can be contracted
(other than sexually transmitted)
can be contracted by using IV drug needles as well as through incident involving the contact of a wound w/ contaminated blood or through childbirth or breast feeding
named the major viral STDs
- Herpes simplex virus
- Human papilloma virus
- Zika virus
- Hepatitis
- Human immunodeficiency
Herpes simplex virus (HSV)
- family
- infects
- structure
- symptoms
- herpesvirus family (Herpesviridae) - HSV-1 and HSV-2
- infects humans; ubiquitous and contagious
- core of ds-DNA surrounded by protein coat in icosahedral symmetry; nucleocapsid surrounded by an envelope
- symptoms
- HSV-1 –> causes oral herpes (cold sores)
- HSV-2 –> genital herpes
what is the most prevalent STD in the US?
genital herpes (HSV-2)
(45 M cases; 1M new genital herpes infxns per year)
epidemiology:
oral herpes and genital herpes
- >100 M Americans have oral herpes;
- > 45 M Americans have genital herpes
- annually, 776,000 people in the US get new herpes infxns
- genital herpes infxn is common; 16% of persons 14-49 y/o have HSV-2 infxn
- inc. # of genital herpes infxns are caused by HSV-1
- increases genital HSV-1 infxn have been found in patient population worldwide
how do people get genital herpes?
(through contact w/ what?)
can it be caught from skin that looks normal?
- thru contact w/ lesions, mucosal surfaces, genital secretions, or oral secretions
- HSV-1 and HSV-2 can both be shed from skin that looks normal;
- in pts w/ asymptomatic HSV-2 infxns, genital HSV shedding occurs on 10% of days
- generally a person can only get HSV-2 infxn during sexual contact w/ someone who has genital HSV-2 infxn
- herpesviruses are highly contagious
symptomology of herpes simplex?
- typically a blister or multiple blisters around infected areas –
- usually the mouth, genitals, or rectum
- blisters break –> leaving tender sores
describe the recurrence of herpes infection:
- what is the process?
- what triggers this?
- how do sxs differ from primary episodes?
- after lesions heal –> virus retreats up nerve fibers and remains dormant in nerve cells of spinal column
- flare-ups: when virus moves down along fibers to genitals/lips
- triggers:
- stress, anxiety, depression
- acidic food, UV light, fever, poor nutrition, fatigue
- general illness (mild to serious conditions)
- immunosuppression due to AIDS or such medications as chemotherapy or steroids
- sxs are generally milder than primary episode and heal more quickly
how to reduce risk of transmission of genital herpes?
- Use condoms – virus can’t pass thru latex condoms
- During outbreak, avoid sexual contact w/ lesion area (even w/ condom - can become infected)
- B/w outbreaks - use condoms still bc there can be asymptomatic viral shedding
- medications are availabel to reduce asymptomatic viral shedding b/w outbreaks –> reduces risk of transmission
herpes complications for:
- women, and
- both sexes?
- women:
- inc. incidence of cervical cancer - women w/ herpes should get pap smears every 6-12 months
- newborn baby can be infected by passage through birth canal – can cause severe damage or death
- C-section recommended for women w/ active symptomatic disease
- both sexes: ocular herpes infection can occur if virus is transferred from a sore to the eye
- must be treated quickly to avoid eye damage
how to prevent and treat herpes?
- prevent: reduce frequency of outbreaks
- suppressive therapy: daily med taken to prevent recurrent outbreaks; reduces asymptomatic viral shedding b/w outbreaks
- treat symptoms of outbreaks, and speed healing
- episodic therapy: medication taken to tx outbreaks when they occur
- using antiviral drugs –> reduce viral shedding & duration/severity of outbreaks
3 antiviral drugs used to tx herpes?
- acyclovir
- valacyclovir
- famiclovir
human papilloma virus:
- family
- infect what?
- symptomology
- papillomavirus family; DNA virus
- establish productive infections only in keratinocytes of the skin or mucous membranes
- symptoms
- most HPV infxns are subclinical and cause no physical symptoms
- some subclinical pts –> can become clinical and cause benign papillomas or cancers of the cervix, vulva, vagina, penis, oropharynx, and anus
clinical symptoms (if present) of HPV
- cause benign papillomas (such as warts [veruccae] or squamous cells papilloma)
- cancers of the cervix, vulva, vagina, penis, oropharynx, and anus
Low-risk HPV types, and their effects
- HPV 6, 11, among others
- Leads to benign cervical changes, and/or genital warts
HIGH-risk HPV types, and their effects
- HPV 16, 18
- lead to:
- precancerous cervical changes,
- cervical cancer,
- anal and other cancers
What about the HPV genome allows the virus to be associated w/ cancer?
contains an oncogene (gene which in certain circumstances can transform a cell into a tumor cell.
also has major viral transforming proteins (E6 and E7)
how does productive HPV infxn progress to malignancy?
- productive life-cycle (2-3 weeks)
- 1-2 years pass
- persistent infxn (lack of immune clearance)
- up to 20 years
- HPV-induced malignancy (oncogene activation +/- integration)
genital warts (GW):
- prevalence
- transmission
- sxs
- treatment
- prev: >15% of Americans/ 6M new US cases/yr
- transmission: sexual contact
- condoms don’t prevent infxn in genital areas not covered by condoms
- HPV is most commonly transmitted by asymptomatic patients
- sxs: *most are asymptomatic
- if visible warts appear, incubation for 3-8 wks after contact
- Women - GW appear in lower vaginal opening, perineum, labia, inner vaginal walls, and cervix
- In men, usually on glans, foreskin, or shaft of penis
- BOTH sexes: can occur on anus
- appear pink/red and soft w/ cauliflower-like appearance in moist areas, OR hard/yellow-gray in dry areas
- if visible warts appear, incubation for 3-8 wks after contact
- tx: visible warts removed by cryotherapy (freezing) or chemical tx –> larger warts may need minor surgery
does cryotherapy and/or surgery prevent recurrence of genital warts?
- removal doesn’t necessarily prevent recurrence
- warts may disappear on their own
what is the underlying cause of cervical cancer?
when was this connection discovered, and by which groups?
HPV is the underlying cause
discovered in 1996 by NIH and WHO
HPV infxns: Summary
(persistent low-risk –>
persistent high -risk –> )
how to prevent cercial cancer?
- screening for precancerous changes (and tx if problems found)
- vaccination against HPV
Hx of the conventional pap smear
- by George Papanicolaou in 1940’s
- most common cancer screening is pap smear
- key part of annual gynecological exam
- has greatly reduced cervical cancer mortality in US
HPV vaccine:
- strains it protects against
- function
- consists of what?
- appropriate age and series
GARDASIL vaccine
- protects against: type 16, 18, 6, 11 (high- and low-risk strains)
- function: prevents HPV infxn, but doesn’t tx existing infxn
- highly effective
- very few serious side effects
- consists of: virus-like particles
- administered before puberty; requires 3 injections
zika virus:
- family/lineages
- structure
- genus: Flavivirus, family: Flaviviridae
- African lineage
- Asian lineage
- enveloped icosahedral, single-stranded RNA virus
what is Zika virus closely related to?
where have outbreaks occurred?
- closely related to Dengue fever (~43% homology & extensive Ab cross-reactivity)
- 1st strain isolated from Rhesus monkey in Zika Forest, Uganda
- Outbreaks in Africa, Asia, and recent outbreaks in Latin/South America
how is Zika virus transmitted?
- vector borne or
- mosquito (from monkey)
- non-vector borne
- accidental lab exposure
- blood trasnfusion
- organ transplant
- monkey bite
- sexual transmission
what can Zika virus cause in newborns?
- microcephaly (small head)
possible neurological and ophthalmic complications of Zika?
- Ophthalmic:
- Conjunctivitis
- Retinal atrophy
- Neurological:
- Meningitis, Meningoencephalitis, myleitis
- Guillain-Barre syndrome (not confirmed)
what is Guillain-Barre syndrome?
can Zika cause this?
strongly associated w/ Zika, but connection is not confirmed
zika virus:
- testing/diagnosis
- primary prevention
- test/dx
- culture for virus
- acute phate (more than 7 days after onset)
- chronic phase (more than 4 days, lasts for months)
- primary prevention
- no vaccine, so prevent mosquito exposure
- people w/ active infxn should avoid exposure to mosquitoes to prevent further spread
hepatits:
- cause
- prevalence
- transmission
- caused by hepatitis virus (types A, B, C, D, E) –> attacks liver
- HepC is most
- prevalence: >170M people have HepC worldwide, 5M in US
- transmission:
- HepA - fecal-oral, oral-anal sexual contact; infected food handlers
- all can be by sexual contact (HepB is more often by sex)
- HepC - *needle sharing
- from infected mother –> fetus/infant
which types of Hep viruses cause Chronic liver disease?
transmission and sxs of the various Hepatitis strains?
- B, C, D, E all can cause Chronic liver disease
Hepatitis:
- sxs
- sequelae
- tx
- vaccines?
- sxs: vary
- asymptomatic
- mild flu-like sxs
- high fever, vomiting, severe abdominal pain
- jaundice/yellowing of whites of eyes or skin due to inc. breakdown of RBC
- sequelae: chronic infxn w/ HepB or HepC –> risk of liver cancer
- HepC –> severe liver complications such as cirrhosis, liver failure (20-25% of patients)
- tx:
- HepA: bed rest, fluid intake
- HepB: same as A, but since can be chronic –> may be tx w/ antiviral drugs
- HepC: more serious –> tx w/ antiviral drugs for some strains
- vaccines?
- Available for HepA and HepC patients
