Chapter 15
Sexually
Transmitted
Infections
STI’s
• Infections that can be transmitted through sexual
activity
• May be caused by a bacteria, virus, fungus, or
other organism
• Some are curable, some are not
• Left untreated, STIs can cause pain, sickness,
infertility, birth defects, and sometimes, death
• STIs are very common (see next slide)
• You can have more than one STI at a time, and you
can get the same STI more than once.
Incidence of STIs
• Startling statistics
– ~1/2 of the STIs diagnosed annually in the US
occur among people under 25
– ~19,000,000 new cases each year in US
– Approximately 3 million teenagers are infected
w/STIs each year
– 25% of U.S. population > 1 STI by age 35
– Largest proportion of AIDS cases infected in
teens or 20s
Factors contributing to high
rates of STIs in the US
• Main reason: multiple sexual partners and
unprotected sex--especially prevalent behavior in
adolescence and early adulthood
• Use of oral contraceptive
• Limited access to health care
• Practitioners do not ask questions about patients’
sexual behaviors
• Some diseases have no obvious symptoms
• Difficulty talking to partner
Info in this chapter
• You will learn about the most common STIs
– Prevalence
– How to recognize them
– What should be done to treat them
– How to avoid contracting or transmitting them
• Information may be graphic at times
• Purpose is not to scare you or discourage
you from exploring joys of sexuality
– Rather, information here is intended to help you
make better decisions and be healthy
For each STI:
• Know what causes it (bacteria, virus, other
organism, etc.)
• Know how it can be transmitted, and how to
avoid transmission
• Know what the symptoms are
• Know how it is treated, if treatment is
available
Size comparison of STI pathogens
Protozoa, lice, scabies mites:
Easily visible under light microscope
Yeast: clearly visible under
light microscope
Bacteria: barely visible under
light microscope
Viruses: not visible under light
microscope
(global)
(from C Wilson Biology of Sexuality lecture)
Bacterial infections
•
•
•
•
•
Chlamydia
Gonorrhea
Nongonococcal urethritis (NGU)
Syphilis
Bacterial vaginosis
Chlamydia
• Caused by: bacterium Chlamydia trachomatis that
infects the urogenital system
• Prevalence: The most common bacterial STI in the
US (3-4 million new cases a yr. in US)
• Transmission: primarily penile-vaginal, oral-genital,
oral-anal, or genital-anal contact; can also be spread
by fingers from one body site to another.
• Symptoms:
– In majority of cases, none!
– if present:
• Women: mild irritation or itching, burning urination, slight
vaginal discharge
• Men: urethral discharge, burning urination
Chlamydia (cont.)
• Consequences if left untreated:
• Women: pelvic inflammatory disease (PID)
– Bacterial infection spreads from cervix up into uterine lining,
fallopian tubes, and possibly ovaries.
– Symptoms of PID include disrupted menstruation, chronic pelvic
pain, lower back pain, fever, nausea, vomiting, and headache.
– Even after treatment, scar tissue from PID can block fallopian
tubes and cause infertility or ectopic pregnancy (very dangerous)
• Men: epididymitis (infection of the epididymis) or urethritis
(infection of the urethral tube)
– Symptoms of epididymitis: heaviness in testis; small, hard,
painful swelling in testis; inflamed scrotum
– Symptoms of urethritis: penile discharge, burning urination
Chlamydia (cont.)
• Consequences if left untreated, cont.:
• Trachoma:
– a chronic, contagious form of
conjunctivitis caused by chlamydia
infection. World’s leading cause
of preventable blindness.
Common cause of eye infections
in newborns, who can become
infected as they pass through
birth canal.
• Consequences for babies born to infected mothers:
– Babies of infected mothers can also develop pneumonia
caused by chlamydia infection
– Chlamydia infection can lead to premature delivery
Chlamydia (cont.)
• Treatment:
• 7-day treatment of doxycycline, or one dose of
azithromycin
• All exposed sexual partners should be treated
Gonorrhea
• Caused by: bacterium Neisseria gonorrhoeae
• Prevalence: ~700,000 new cases a yr. in US
• Transmission: penile-vaginal, oral-genital, oral-anal,
or genital-anal contact
• Symptoms:
– Male early symptoms:
• foul-smelling, cloudy penile discharge,
• burning urination
• symptoms may clear up, but does not
necessarily mean bacteria are gone
– Female early symptoms:
• usually go undetected
• inflamed cervix, mild discharge
• burning urination
Gonorrhea (cont.)
• Consequences if left untreated:
• Men: prostate abcesses, painful BMs, difficult
urination, possible sterility due to scar tissue in
epididymis after epididymitis
• Women: PID (often more severe than w/chlamydia
infection), ectopic pregnancy, severe pelvic pain due
to scar-tissue adhesions across pelvis
• Both sexes: can enter bloodstream and spread
throughout body in ~2% of cases, causing fever, loss
of appetite, arthritic pain, can invade heart, liver, CNS
– Can cause blindness in infants (due to conjunctivitis)
Gonorrhea (cont.)
• Treatment:
• Dual therapy of two antibiotic regimens
• Often, chlamydia infections accompany
gonorrhea infection--dual therapy will treat both
infections
• Resistant bacteria require special treatment
• All exposed sexual partners should be treated
Nongonococcal Urethritis
• Any urethral inflammation not caused by gonorrhea
– Main infecting organisms: Chlamydia trachomatis and
Mycoplasma genitalium
– Can also result from other infectious agents, allergic
reactions to vaginal secretions, or irritation from soaps,
contraceptives, or deodorant sprays
• Prevalence: quite common in men; symptoms in
women are usually undetected
• Transmission: mainly through penile-vaginal coitus
• Symptoms:
– Men: penile discharge, burning urination
– Women: frequently, no symptoms; may have mild
itching, burning urination, vaginal discharge of pus
Nongonococcal Urethritis (cont.)
• Consequences if left untreated:
• Men: can spread to prostate, epididymis, or both
• Women: cervial inflammation, PID
• Treatment:
• 7-day treatment of doxycycline, or one dose of
azithromycin
• All exposed sexual partners should be treated
Syphilis
• Caused by: bacterium Treponema pallidium
• Prevalence: ~700,000 new cases a yr. in US
• Transmission: penile-vaginal, oral-genital, oral-anal,
or genital-anal contact
• Symptoms:
– Primary syphilis: Single, painless sore (chancre)
– Women: on inner vaginal walls or cervix, sometimes on labia
– Men: glans of penis, penile shaft, or scrotum
– Can also occur on lips or tongue (infected orally) or in
rectum/anus (infected through
anal intercourse)
Glans of penis
labia
anus
• Symptoms:
Syphilis (cont.)
– Secondary syphilis: skin rash,
– often on palms, soles of feet
•
•
•
•
•
Severity can vary from barely
noticable to severe
Does not hurt or itch
Person may feel flu-like symptoms
If not treated, symptoms will subside,
disease is not eliminated
but
– Latent syphilis: no symptoms; no longer contagious
after 1 year of latent stage (except pregnant woman to
fetus--at all stages)
– Tertiary syphilis: severe symptoms anywhere--such as
heart failure, blindness, paralysis, liver damage, mental
disturbance, death
Syphilis (cont.)
• Treatment:
• Primary, secondary, or latent syphilis (< 1yr)
early cases treated with benzathine penicillin G
or other antibiotic
• All exposed sexual partners should be treated
• Treated patients need blood tests at 3-month
intervals to make sure they are free of bacterium
• To prevent birth defects, death to fetus, it is
recommended that all pregnant women are
tested for syphilis at first prenatal visit
Viral infections
• Herpes Simplex Virus (HSV)
• Human papillomavirus (HPV)
– a.k.a. genital warts
• Hepatitis
– 3 types (HAV, HBV, HCV)
• Human immunodeficiency virus (HIV)
Herpes
• Caused by: Herpes simplex virus (HSV)
– Two sexually transmitted types: HSV-1 and HSV-2
– HSV-1 is usually oral herpes (cold sores), but can infect
genitals; HSV-2 usually causes genital lesions, but can
also infect the mouth
• Prevalence: >100 million Americans have oral herpes;
>45 million Americans (20-25%) have genital herpes
• Transmission:
– Genital herpes: penile-vaginal, oral-genital, oral-anal, or
genital-anal contact
– Oral herpes: through kissing, or oral-genital contact
– Herpes sores are highly contagious--need to avoid contact
between lesions and someone else’s body
– Can still transmit herpes even if no lesions are present
Herpes (cont.)
• How to reduce risk of transmission:
– Herpes virus cannot pass through latex condoms
– During an outbreak (for most people, ~3 times/yr), best to
avoid sexual contact with the lesion area--condoms
should not be relied on when lesions are present
– Between outbreaks--safest strategy is to use condoms,
oral dams, etc. since there can sometimes be
asymptomatic viral shedding
• Condoms aren’t 100% effective at preventing transmission,
since they don’t cover entire genital area, but they reduce risk
significantly
– Medications are available that reduce the amount of
asymptomatic viral shedding that occurs between
outbreaks--can significantly reduce risk of transmission
• Recurrence:
Herpes (cont.)
– After lesions heal, virus retreats up nerve fibers and stays
dormant in nerve cells in the spinal column
– Flare-ups occur when virus moves back down along fibers to
genitals or lips
– Triggered by wide variety of factors, such as: stress, anxiety,
depression, acidic food, UV light, fever, poor nutrition, fatigue
– Symptoms during recurrent attacks tend to be milder than
primary episode, heal more quickly
– Prodromal symptoms: symptoms that warn of an impending
herpes outbreak
• Burning, throbbing, or tingling at sites of infection
• Sometimes includes pain in legs, thighs, groin, or buttocks
• Viral shedding is more common during prodromal symptoms than
beforehand--best to avoid contact w/infected area from first sign of
prodromal symptoms until sores have healed
Herpes (cont.)
• Other complications:
• Women:
– Increased incidence of cervical cancer--women with
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
• Treatment:
Herpes (cont.)
• Reduce frequency of outbreaks
• Treat symptoms of outbreaks and speed healing
• Two types of therapies
– Suppressive therapy: medication taken daily to prevent
recurrent outbreaks; also reduces asymptomatic viral
shedding between outbreaks
– Episodic treatment: medication taken to treat outbreaks
when they occur
• Antiviral drugs-- reduce viral shedding and the
duration and severity of outbreaks
– Acyclovir (trade name Zovirax)
– Valacyclovir (trade name Valtrex)
– Famiclovir (trade name Famvir)
Genital warts
• Caused by: Human papilloma virus (HPV)
– There are over 100 strains, ~1/2 cause genital infections
• Prevalence: >15% of Americans; >6 million new cases in
US each year
• Transmission:
– Penile-vaginal, oral-genital, oral-anal, or genital-anal
contact
– Condoms do provide some protection, but don’t prevent
transmission of viral infections on vulva, base of penis,
scrotus, and other genital areas not covered by condoms
– HPV is most commonly transmitted by people who are
asymptomatic
Genital warts (cont.)
• Symptoms:
– Most people don’t develop symptoms
and are unaware that they are infected.
– If visible warts do appear, incubation
period is approximately 3-8 weeks after
contact w/infected person.
• In women, genital warts usually appear on
lower vaginal opening--also,perineum, labia,
inner vaginal walls,cervix
• In men,usually on glans,foreskin,or shaft of
penis. Both sexes: can also occur on anus.
In moist areas, appear pink or red and
soft,w/cauliflower-like appearance; in dry
areas, appear hard and yellow-gray
Genital warts (cont.)
• Consequences:
• Certain strains of HPV are associated with cancers of
the cervix, vagina, vulva, urethra, penis, & anus
• HPV infections account for 85-90% of risk for
development of cervical cancer
– Risk of HPV-induced cervical cancer is minimal if regular
Pap testing and treatment of precancerous lesions is done
• Pregnant women that are + for HPV can transmit the
virus to their babies during birth
– Can cause respiratory papillomatosis in infants--HPV
infection of upper respiratory tract
Genital warts (cont.)
• Treatment:
• Visible genital warts are removed by either cryotherapy
(freezing) or chemical treatment; larger warts may require
minor surgery to remove
– Removal doesn’t necessarily prevent recurrence
– Warts may disappear on their own
• New: prevention via vaccine
• Gardisil: vaccine against 4 strains of HPV that together
cause 70% of cervical cancers and 90% of genital warts
• US Dept. of Health and Human Services committee voted
unanimously that females age 11-26 should be vaccinated
– Most health officials believe vaccination before puberty is best, before
teens become sexually active
Hepatitis
• Caused by: Hepatitis virus--attacks the liver
– There are three types, each caused by a different hepatitis virus,
hepatitis A (most common), hepatitis B, and hepatitis C
• Prevalence: worldwide, >170 million people (5 million in US)
have HepC infection (the most health-threatening of the 3 types)
• Transmission:
– All 3 types of hepatitis can be transmitted through sexual
contact, but HepB (and somewhat, HepA)are transmitted more
often through sex
– Needle-sharing is also a common mode of transmission (most
common mode of transmission for HepC)
– HepA spread primarily through fecal-oral route
• Oral-anal sexual contact
• Infected food handlers not washing hands after using bathroom
– From infected mother to fetus or infant
Hepatitis (cont.)
• Symptoms:
– Symptoms vary considerably:
•
•
•
•
May have no symptoms
May have mild flu-like symptoms
May have high fever, vomiting, severe abdominal pain
Jaundice can occur--yellowing of whites of the eyes or the skin
due to increased breakdown of RBC.
• Consequences:
• Chronic infection w/HepB or HepC is a major risk factor for
liver cancer
• ~20-25% of HepC+ people manifest progressive disease
resulting in severe liver complications--liver cancer,
cirrhosis, liver failure
• Treatment:
Hepatitis (cont.)
• HepA: bed rest, fluid intake--usually runs its course in a few
weeks to a few months
• HepB: same as HepA, except that some HepB infections can
become chronic and persist for >6 months
– Chronic HepB infections are treated w/several antiviral drugs
• HepC: more serious for the 20-25% of HepC+ people with
progressive chronic HepC infection--antiviral drugs can help
somewhat for some strains of HepC (especially AIDS
patients)
• Vaccines
• Available for HepA and HepB
– High risk people (health care workers, injection drug users, sexually
active people w/multiple sex partners, etc.) should be immunized
– CDC recommends that children be immunized for HepB
Common Vaginal Infections
• Vaginitis: general term applied to variety of
vaginal infections
– May be caused by organisms that are already present in
vagina
• Sexual activity may introduce organism, or may throw off balance
of ‘good’ microbes in the vagina
– Bacterial vaginosis: caused by anaerobic bacteria,
Mycoplasma bacteria, or Gardnerella vaginalis
– Candidiasis: caused by yeast infection w/Candida
albicans
– Trichomoniasis: caused by one-celled protozoan
Trichomonas vaginalis
Bacterial vaginosis (BV)
• Very common vaginal infection
• Occurs more frequently among sexually active women,
though can occur in women who have not experience
sexual intercourse
• Symptoms (in women): foul-smelling pasty discharge,
usually gray, can be white, yellow, or green
– Most men are asymptomatic--some develop urethritis or bladder
infection
• If untreated, can increase risk of PID
• If untreated in pregnant woman, associated w/ premature
rupture of amniotic sac, preterm labor
• Treatment w/oral or topical Flagyl (metronidazole) or
clindamycin cream
Candidiasis
• Also very common vaginal infection--3/4 of women will
have at least one genital yeast infection in their lifetime
• Candida albicans yeast are normally present in the vagina
of many women--also present in mouth and intestines of
many people
– Only causes infection/disease when yeast becomes overgrown
– Can occur during pregnancy, from antibiotics, spermicidal
creams, oral contraceptives, high-sugar diet, diabetes
• Symptoms (in women):
– white, clumpy, cottage-cheese discharge
– Intense itching and soreness of vaginal and vulval tissues
• Treatment: topical intravaginal creams, available over the
counter--wise to be diagnosed by a doctor first;
– many women self diagnose incorrectly
Trichomoniasis
•
•
•
•
Common in women and men
7-8 new cases each year in US
Primarily spread through sexual contact
Symptoms (women):
Trichomonas
vaginalis
– White or yellow-green discharge, frothy, w/unpleasant odor
– Irritated vaginal and vulval tissues -- can increase a woman’s
susceptibility to HIV infection
– If untreated, can damage cervical cells, may lead to cervical
cancer; in pregnant women, can lead to premature rupture of
amniotic sac and preterm delivery
• Symptoms (men): usually none, may have frequent or
painful urination or slight urethral discharge
• Treatment: metronidazole (Flagyl)
– All sexual partners should be treated
Ectoparasitic infections
• Ectoparasites: parasitic organisms that live
on the outer skin surfaces
• 2 common STIs caused by ectoparasites:
1) pubic lice
2) scabies
Pubic lice (a.k.a. crabs)
• Caused by: biting louse called
Phthirius pubis
• Prevalence: more prevalent
among young (15-25 yr.old)
single people, often associated
w/presence of other STIs.
Female pubic louse
• Transmission: during sexual contact when two
people bring their pubic areas together
– Lice can live away from the body for as long as 1 day--can
drop off onto underclothes, bedsheets, etc, and eggs
deposited by female louse can survive for several days
• Therefore, it is possible to get pubic lice by sleeping in someone’s
bed or wearing someone’s clothes
Pubic lice (cont.)
• Symptoms:
– Itching (that’s not relieved by
scratching)
– Can also leave bluish-grayish
marks on the thighs and pubic
area from bites
– Self-diagnosis is possible by locating
a louse on a pubic hair
• Treatment:
– medicinal lotion (1% permethrin or pyrethrin) applied to all
affected areas + all areas w/body hair (genitals, armpits,
scalp, even eyebrows);
– wash all clothes and bedding that were exposed
Scabies
• Caused by: parasitic mite called
Sarcoptes scabiei
– Female mite burrows beneath skin
to lay eggs--hatched egg grows into
adult that on host’s skin
– Too small to be seen by naked eye
Scabies mite
• Prevalence: not reported to health agencies--worldwide,
estimated at ~300 million cases/yr.
• Transmission:
– by close physical contact, both sexual and nonsexual
– Can be transferred on clothing or bedding (can live away
from host for up to 3 days)
– In addition to sexually active people, school children,
nursing home residents, and indigent people are at risk
• Symptoms:
Scabies (cont.)
– Small vesicles or pimple-like
bumps, red rash
– Intense itching
– Favorite sites of infestation:
webs and sides of fingers, wrists,
abdomen, genitals, buttocks,
and female breasts
• Treatment:
– medicinal lotion (prescription & nonprescription available)
applied at bedtime, then washed off after 8 hrs
– wash all clothes and bedding that were exposed
Aqcuired immunodeficiency sydrome
(AIDS)
• Caused by:
• Infection w/the human immunodeficiency virus (HIV)
• 2 strains, HIV-1, and HIV-2: HIV-1 is more virulent and
causes most cases in US; HIV-2 exists along w/HIV-1 in some
African countries
• History
• Research indicates that HIV originated from a subspecies of
chimpanzees that reside in central/SW Africa
– Chimps harbor a simian immunodeficiency virus (SIV) that genetically
converted to HIV
• HIV evolved from SIV sometime around 1931, but likely
remained confined to a small isolated population
– Eventually, migration into large cities and global travel spread the virus
worldwide
HIV & AIDS
• HIV = a retrovirus that
• targets & destroys helper
Tcells
(aka helper T-4 or CD4 cells)
– T cells play a very important
role in the immune system
– Therefore, HIV infection
leaves the body vulnerable
to a variety of opportunistic infections and cancers
• HIV becomes AIDS when:
– HIV is present, and
T-4 cell count is < 200 cells/microliter
of blood (normal T-4 counts are
600 - 1,200 cells/microliter of blood)
T-4 cell under attack by HIV
HIV/AIDS: prevalence in U.S.
• >1 million cases reported as of Jan 2006
• > 525,000 people died of AIDS since first diagnosis
• Estimated ~1.2 million people currently HIV+, and ~25 50% of these people are unaware of their HIV status
• Overall rate of new HIV infections in US has slowed, but
number of new infections among teenagers, women, and
racial and ethnic minorities continues to rise
– Teenagers: multiple sexual partners, less likely to have access
to or to use condoms; substance abuse, feel invulnerable
– Ethnic and racial minorities: reduced access to health care,
cultural or language barriers to information about STI prevention,
differences in high-risk behaviors
– Women: fastest-growing HIV-infected population in US.--HIV
more easily transmitted from men-to-women than vice versa
Women and HIV/AIDS
• Number of women infected w/HIV is steadily increasing
• Women are more easily infected from heterosexual
intercourse w/and HIV+ partner than men are
– Semen contains higher concentration of HIV than vaginal fluids
– Female mucosal surface is exposed to HIV in ejaculate longer
than a man’s penis is exposed to HIV in vaginal secretions
– Larger area of mucosal surface is exposed in vagina/on vulva
than on the penis
– Female mucosal surface is exposed to greater potential trauma
than the penis--can cause small tears that allow virus to enter
– Some women have unprotected receptive anal intercourse--the
single-most risky behavior in terms of HIV infection for both men
and women
– Adolescent women are more vulnerable to HIV infection b/c their
reproductive tracts are immature--more susceptible to infection
Global HIV/AIDS
•
•
•
•
•
•
5 million new HIV infections occur globally
By end of 2005, ~40.3 million people infected
AIDS kills
>3 million
people
each year
AIDS in Africa
• AIDS has reached epidemic proportions in subSaharan Africa; >15% of all adults are HIV+
– 2/3 (25.8 million) of all people living w/AIDS live in subSaharan Africa
– over 80% of AIDS deaths have occurred in Africa, primarily
sub-Saharan Africa
– 75% of HIV infections in African youth are of females
– over 10.5 million AIDS orphans in sub-Saharan Africa
• Factors contributing:
– Widespread poverty, lack of medical care, widespread
ignorance about HIV prevention
– Cultural factors, gender roles
– General feeling of hopelessness
AIDS: Transmission
• HIV in bodily fluids:
– blood, semen, vaginal secretions, breast milk
– NOTE: saliva, urine, tears--concentration of virus (if any) way too
low to transmit infection.
• Can be transmitted:
– Through vaginal or anal intercourse or oral-genital contact
– Through contaminated blood (needles, blood transfusion)
– From mother to fetus before birth, infant during birth or after
through breastfeeding
• Likelihood of transmission during sexual contact:
– Depends on infected person’s viral load (#virus particles
per ml of blood)
– Is greater when HIV is transmitted directly into blood,
(through small tears in rectal tissues or vaginal walls)
HIV/AIDS: symptoms & complications
• Within few weeks of infection, can cause flu-like
symptoms in some people
• As virus depletes immune system:
– Persistent or periodically repeating fevers,
night sweats, weight loss (“wasting syndrome”)
– Opportunistic infections
• oral candidiasis
• Life-threatening pneumonia caused by Pneumocystis carinii, which
normally inhabits lungs of healthy people
• Others: TB, encephalitis, toxoplasmosis
• Cancers: lymphomas, Kaposi’s sarcoma
• Time from HIV infection to onset of AIDS
typically ranges from 8 - 11 yrs; new treatments can
dramatically slow progression of HIV to AIDS
HIV: symptoms & complications
• Note: viral load is highest immediately after infection,
and at late stages of HIV progression
HIV/AIDS: Treatment
• HIV treatment drugs inhibit
two major viral enzymes
(cell proteins that carry out
chemical reactions)
1) Reverse transcriptase
– Enzyme that converts HIV
RNA genome into DNA
so it can insert into our own
DNA
2) Protease
– New HIV proteins are produced in the form of long chains
that need to be cut into smaller pieces to assemble into
new HIV viruses
– Protease enzyme is the “scissors” for this process
Drug therapy to prevent mother-tochild transmission (MTCT) of HIV
• Zidovudine (an RT inhibitor) can reduce MTCT by 2/3 if
given to both HIV-infected mothers & their newborns
– Drug is given orally to pregnant women during gestation, by IV
during labor, and orally to newborn for first 6 weeks of life
– # of infants infected through MTCT in U.S. has declined
dramatically due to widespread use of this treatment
– Treatment regimen is very costly, and involves multiple
treatments, making it hard to administer in many poorer
countries
– Recent studies in S. Africa & Uganda: infants given either a
single dose or a short-course regimen of nevirapine (RT
inhibitor) experienced excellent protection from HIV infection
– Infected mother must still refrain from breastfeeding to avoid
infecting newborn
The search for a vaccine
• Vaccine: a harmless variant or protein/DNA fragment
from a pathogen (e.g. the HIV virus) that prevents
infection by the pathogen by stimulating the immune
system to develop long-lasting defenses.
• Several attempts have been made to develop a
vaccine against HIV--so far, w/disappointing results
• Many more vaccine candidates (over 30 as of 2005)
are currently being tested
• Many challenges confront vaccine researchers:
– Absence of ideal animal model for research
– HIV is a very complicated virus w/multiple strains
– HIV can change rapidly through genetic mutation
Preventing STIs
• Only sure-fire way is abstinence, or monogamous
relationship btwn 2 uninfected people
• Get tested for STIs, insist that your partner do too
– May want to wait for results before engaging in sexual
activity that can put you at risk
• Communicate w/partners about safe sex
– Get to know potential sexual partners well
enough to develop trust and communication
– Inform a partner if you have an STI
• Avoid sex w/multiple partners or
w/individuals at high risk for STIs
• Use condoms or oral dams
• If you use injected drugs, do not share
needles
Condoms
• Latex condoms are highly effective in
preventing transmission of HIV,
chlamydia, gonorrhea, NGU,
bacterial vaginosis, and trichomoniasis
– Condoms are less effective in preventing infections
transmitted by skin-to-skin contact, such as syphilis, herpes,
HPV, and are ineffective in preventing pubic lice and scabies
– Condoms from sheep’s membrane contain small pores that
may permit passage of viruses (HIV, HSV, hepatitis)
– Studies on couples where one partner is infected show that with
consistent condom use, HIV infection rates for the uninfected
partner are below 1% per year.
• CDC recommends against using condoms containing
nonoxynol-9 (N-9), which can cause genital lesions that
create an entry point for HIV and other STI pathogens
Proper use of condoms
Condoms must be used correctly every time!
Proper use of condoms
• Store condoms in a cool, dry place away
from direct sunlight
• Throw away condoms past expiration
date or condoms in damaged packages
• Put on a condom before any genital
contact occurs
• Be sure that the condom is adequately lubricated--if you add
lube, use only water-based lube (oil-based lubes deteriorate latex)
• Unroll condom directly onto erect penis; if penis is
uncircumcised, pull back foreskin before putting on condom
• After ejaculation, hold base of condom before withdrawal so
condom does not slip off
• Note: rates of condom slippage and breakage are higher
during anal intercourse than vaginal intercourse, so be extra
careful during anal penetration