Sexually Transmitted Diseases

Incidence

Estimated number of new cases of a disease per year

Prevalence

Estimated number of people currently infected with a given disease per year

Pubic lice (crabs)

• Small but visible insects (~1mm) that typically live in pubic hair but can spread to other hairy areas of the skin (move by clinging on to two strands of hair)

• Feed on the blood of the host

• Possible to acquire either through direct contact or by using an infested person’s bedding, clothing, etc.

• Mainly cause itching

• Typically treated with insecticidal lotion or removed by shaving

Scabies mites

• Infestation with a parasitic mite (Sarcoptes scabiei)

• Dig tunnels within the upper layers of the skin, commonly found in hairless areas such as wrists, elbows, between fingers, knees, penis, breasts

• Lay their eggs beneath the skin

• Cause severe itching and rash on skin

• Spreads easily between people

• Treated with medicated lotion

Trichomoniasis

• Infection of the vagina or male urethra and prostate gland with a single-celled protozoa

• In women, infection marked by foul-smelling, greenish, or frothy discharge from vagina, itching and redness, abdominal discomfort, and urge to urinate frequently

• Men are usually asymptomatic, though women may also be

• Transmission occurs through coitus

• Estimated 2 million women develop infection per year

• Cured with a single dose of metronidazole

Bacterial STDs

• Main examples in US are syphilis, gonorrhea, and chlamydia

• Can be fatal (syphilis), impair fertility (gonorrhea & chlamydia)), or facilitate HIV infection (all 3)

• All are curable when treated promptly, usually with antibiotics

Syphilis

• Spread via direct contact (usually sexual) with infected person in primary or secondary stage

  • Can be transmitted from mother to fetus

  • Spread via contact with fluid from sores (chancres) which appear at infection site within 10-90 days

• There are 4 stages: primary, secondary, latent, tertiary

• Can be diagnosed by clinical signs and symptoms (bacterial fluid in discharge from chancre or antibodies to T. pallidum in blood)

• Single large injection of penicillin is curative in first year of infection

• Epidemic among heterosexual African Americans in the south and gay/bi men in cities, as well as 13% of all new cases being reported in prisons

Primary syphilis

Chancre appears at infection site within 10-90 days and heals within 3-6 weeks. This is the stage in which the individual is most infectious.

Secondary syphilis

Painless rash following the chancre healing that disappears within a few weeks. Individual is still highly infectious.

Latent stage of syphilis

Bacteria continues to multiply in the body and invades the cardiovascular system, bones, liver, and nervous system. Less infectious during this stage.

Tertiary stage of syphilis

Large ulcers appear on skin or organs after having already covered internal organs. Usually too late to treat at this stage. No longer highly contagious.

Tuskegee Syphilis Study

• Significantly eroded minority groups’ trust in US medicine

• 1932 - study of effects of untreated syphilis began on hundreds of African American men in Tuskegee, Alabama (they were not told they had syphilis)

• 1947 - penicillin was recognized as standard of care for syphilis, but subjects in study were not informed or treated

• 1972 - CDC whistleblower told the media, at which point dozens of subjects had died and 22 wives, 17 children, 2 grandchildren had contracted syphilis

gonorrhea

• Symptoms develop within 2-10 days of infection

• Caused by Neisseria gonorrhoeae bacteria

• In women, infection site is cervix

  • Symptoms include yellow or bloody vaginal discharge, bleeding during coitus, burning sensation when urination

  • Infection can spread into the uterus and oviducts causing pelvic inflammatory disease (PID) and infertility

• In men, infection site is the urethra

  • Symptoms include discharge of pus from the urethra, pain during urination

  • Infection can spread to the epididymis or prostate gland (can potentially cause infertility in men)

• Used to be treated readily with standard antibiotics, but bacterium has developed drug resistance and CDC recommends all cases be treated with Cephalosporins (special class of antibiotics)

• ~700,000 new cases reported in US every year; must prevalent in the South

Chlamydia

• Most common of all reportable infectious diseases

• Usually spread by genital contact, but may be spread by insects in tropical countries (cause of blindness)

• Symptoms appear within days

  • Women - infection appears in the cervix or urethra causing discharge, painful urination

  • Men - infection appears in urethra causing discharge and burning pain during urination

  • 75% women and 50% men are asymptomatic

• Diagnosed from cell samples from penis or cervix, or urine samples

• Can be treated with a single dose of antibiotics

• Very common in young women - CDC recommends that all sexually active women under 25 be tested once per year

  • 1 in 10 of all adolescent girls is infected

Bacterial Vaginosis

• Status as an STD has been up for debate until recently

• Normal vaginal microorganisms are replaced by other bacteria

  • Vaginal pH becomes less acidic

  • Vagina develops fishy odor, may be itching, pain, and off-white discharge

  • Many women have no symptoms

• Very common among sexually active women (particularly WSW)

Viral STDs

• Extremely small infectious particles that enter a host cell

• Once in host cell, viral genes take over and either replicate immediately or after being inactive for a period of months to years

• NOT treatable with antibiotics, and antiviral drugs are rarely curative and extremely expensive with serious side effects

• 6 main classes: pox, herpes simplex, CMV, HPV, hepatitis, HIV

Molluscum contagiosum

• Skin condition caused by a pox virus

• Characterized by small, bump-like growths on the skin which are highly contagious

• Virus transmitted by skin-to-skin contact or by contact with infected clothing or towels

• Nonsexual transmission is common, especially among children

• Does not cause any serious health condition and usually disappears within a year

  • No serious long-term effects

Genital herpes

• Two herpes viruses (HSV-1 and HSV-2) may be transmitted sexually

• Lifelong infection, most common STD by prevalence

• 17% of Americans aged 14-49 are infected with HSV-2, and 90% are unaware that they’re infected (asymptomatic)

• Outbreaks typically preceded by tingling or itching at infection site, and first outbreak may include fever and swollen lymph nodes

  • Reddish bumps or cluster of spots appear, which turn into blisters within 24 hours, or cracks in the skin

  • Blisters break leaving sores or ulcers that leak clear discharge containing viral particles (may be painless or mildly itchy)

• Diagnosed via lab tests on samples from sores or blood

• Treated with acyclovir (Zovirax), available as a topical ointment and the more effective oral tablets

• Considered incurable with current therapy

HSV-1

• Commonly causes oral herpes, often in form of “fever blisters” or cold sores on lips

• May be spread by sexual or nonsexual contact, can be transmitted through touch

• Infections of this type have been increasing, possibly due to the popularity of oral sex

• Less severe version

HSV-2

• Common cause of the more serious genital herpes

• Usually transmitted by anogenital contact

• Initial symptoms occur within 2 weeks after exposure (outbreak of sores at infection site)

• Genitals are most frequently affected sites (penis, labia, clitoral hood, vaginal walls)

• Most serious outbreak occurs the first time an individual is exposed

HSV-2 recurrent outbreaks

• Primary herpes infection typically resolves within 2 weeks and the sores disappear

• Virus remains inert within nerve cell bodies

• Later outbreaks typically less severe and less frequent

• Virus mainly transmitted during outbreaks, but can also happen between them

Cytomegalovirus (CMV)

• DNA virus related to HSV

• Most people don’t show symptoms 9estimated 50-80% of population infected with it at some point)

• Very easily transmitted in bodily fluids

  • Daycare and nursery school workers are at risk

  • Mother-to-fetus transmission is possible

Human papillomaviruses (HPV)

• 100 different types of DNA viruses, 30 of which are sexually transmitted

• Viruses infect cells lining urogenital tract or skin near genitalia, can remain inactive or trigger cell division leading to genital warts or sin lesions

  • Many infected people are asymptomatic

• Genital warts are highly infectious and usually painless, don’t cause serious health problems, 90% caused by types 6 and 11

• Infection with types 16 and 18 is the main cause of cervical cancer (70%), and linked to anal, mouth/throat, vulval cancer

• Not likely for mother to pass along to fetus

• Most common STD in the US by incidence (50-57% of sexually active individuals)

• Most infected individuals eventually clear the virus from their bodies and become noninfectious to others within 2 years of initial infection

• Gardasil - 1st vaccine against HPV types 6,11,16,18

Hepatitis viruses

• Viruses that attack the liver - Hep B, followed by Hep A, are the most likely to be sexually transmitted

• Vaccines available against both types:

  • Combined: 3 injections over 6 months

  • Costs $120 on average without insurance

Hepatitis B

• DNA virus that can be transmitted via sex or contaminated blood

• Symptoms include jaundice

• Most people recover, but some become “chronic” and remain infectious

• Treated via drugs taken for months (suppress symptoms but don’t get rid of the virus)

Hepatitis A

• RNA virus transmitted most often by fecal-oral route (sexual or nonsexual transmission)

• Similar symptoms to Hep B but milder

• Disease cannot progress to chronic state and individual does not remain infectious after recovery - no specific treatment

AIDS (Acquired Immune Deficiency Syndrome)

• First described in 1981, fatal if left untreated → now an epidemic across the world

• Caused by HIV (human immunodeficiency virus) - an RNA virus

  • Evolved from similar virus that infects chimps in west-central Africa, spread to humans around the 1950s, first major outbreak in gay communities in SF, LA, and NYC in late 1970s

• AIDS is the name of the syndrome acquired after the HIV virus becomes active - not everyone infected with HIV develops AIDS today

• When the level of CD4 cells in blood is at or below ~200/uL, the person is considered to have AIDS

• Symptoms: acute flu-like condition; after latent period, opportunistic infections, cervical cancer, lymphoma, wasting

• Diagnosed through blood test (antibodies to virus or DNA test)

• Treated through combination of several oral antiviral drugs (HAART) - not curable

  • Preventative care through PrEP has been highly effective

HIV

• Present in high concentrations in semen and vaginal fluid

• Transmission occurs more readily in penis-to-vagina or penis-to-anus directions, risk of transmission to receptive partner is 5x higher for anal sex than coitus due to micro-tears in anus being more likely

• Presence of existing STDs increases risk

• Virus mainly targets CD4 lymphocytes - white blood cells in immune system

• Seroconversion: person does not test positive for HIV until antibodies appear in blood (usually 6 weeks - 6 months after infection)

• Symptoms subside after antibodies form and person enters asymptomatic period for 7-10 years

• Level of CD4 cells in blood gradually decline from normal level of 1000/microlitier to ~200/uL, when the person is considered to have AIDS

• Disproportionately affects MSM and African American communities