Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Sexually transmitted diseases (STDs)

513

•

Genital herpes is a widespread, recurrent, and incurable

viral infection. Almost a million new cases are reported in the

United States annually. The prevalence of herpes infection

reflects the highly contagious nature of the virus. About 75%

of the sexual partners of individuals with the infection develop

genital herpes.

The herpes virus is common. Most individuals who are

exposed to one of the two types of herpes simplex virus never

develop any symptoms. In these cases, the herpes virus

remains in certain nerve cells of the body, but does not cause

any problems. Herpes simplex virus type 1 most frequently

causes cold sores on the lips or mouth, but can also cause gen-

ital infections. Herpes simplex virus type 2 most commonly

causes genital sores, though mouth sores can also occur due to

this type of virus.

In genital herpes, the virus enters the skin or mucous

membrane, travels to a group of nerves at the end of the spinal

cord, and initiates a host of painful symptoms within about

one week of exposure. These symptoms may include vaginal

discharge, pain in the legs, and an itching or burning feeling.

A few days later, sores appear at the infected area. Beginning

as small red bumps, they can become open sores which even-

tually become crusted. These sores are typically painful and

last an average of two weeks.

Following the initial outbreak, the virus waits in the

nerve cells in an inactive state. A recurrence is created when

the virus moves through the nervous system to the skin. There

may be new sores or simply a shedding of virus which can

infect a sexual partner. The number of times herpes recurs

varies from individual to individual, ranging from several

times a year to only once or twice in a lifetime. Occurrences

of genital herpes may be shortened through use of an antiviral

drug which limits the herpes virus’s ability to reproduce itself.

Genital herpes is most dangerous to newborns born to

pregnant women experiencing their first episode of the dis-

ease. Direct newborn contact with the virus increases the risk

of neurological damage or death. To avoid exposure, physi-

cians usually deliver babies using cesarean section if herpes

lesions are present.

Hepatitis, an inflammation of the liver, is a complicated

illness with many types. Millions of Americans develop hepa-

titis annually. The hepatitis A virus, one of four types of viral

hepatitis, is most often spread by contaminationof food or

water. The hepatitis B virus is most often spread through sex-

ual contact, through the sharing of intravenous drug needles,

and from mother to child. Hospital workers who are exposed

to blood and blood products are also at risk. Hepatitis C and

Hepatitis D (less commonly) may also be spread through sex-

ual contact.

A yellowing of the skin, or jaundice, is the best known

symptom of hepatitis. Other symptoms include dark and

foamy urine and abdominal pain. There is no cure for hepati-

tis, although prolonged rest usually enables individuals with

the disease to recover completely.

Many people who develop hepatitis B become carriers

of the virus for life. This means they can infect others and face

a high risk of developing liver disease. There are as many as

350 million carriers worldwide, and about 1.5 million in the

United States. Avaccinationis available against hepatitis B.

The link between human papillomavirus, genital warts,

and certain types of cancer has drawn attention to the potential

risk of genital warts. There are more than 60 types of human

papillomavirus. Many of these types can cause genital warts.

In the United States, about 1 million new cases of genital

warts are diagnosed every year.

Genital warts are very contagious, and about two-thirds

of the individuals who have sexual contact with someone with

genital warts develop the disease. There is also an association

between human papillomavirus and cancer of the cervix, anus,

penis, and vulva. This means that people who develop genital

warts appear to be at a higher risk for these cancers and should

have their health carefully watched. Contact with genital warts

can also damage infants born to mothers with the problem.

Genital warts usually appear within three months of

sexual contact. The warts can be removed in various ways, but

the virus remains in the body. Once the warts are removed the

chances of transmitting the disease are reduced.

Many questions persist concerning the control of sexu-

ally transmitted diseases. Experts have struggled for years

with efforts to inform people about transmission and treatment

of sexually transmitted disease. Frustration over the continu-

ing increase in sexually transmitted disease is one factor

which has fueled interest in potential vaccines against certain

sexually transmitted diseases.

A worldwide research effort to develop a vaccine

against AIDS has resulted in a series of vaccinations now in

clinical trials. Efforts have focused in two areas, finding a vac-

cine to protect individuals against the HIV virus and finding a

vaccine to prevent the progression of HIV to AIDS in individ-

uals who already have been exposed to the virus. One of many

challenges facing researchers has been the ability of the HIV

virus to change, making efforts to develop a single vaccine

against the virus futile.

Researchers also are searching for vaccines against

syphilis and gonorrhea. Experiments conducted on prisoners

more than 40 years ago proved that some individuals could

develop immunity to syphilis after inoculation with live

Treponema pallidum, but researchers have still not been able

to develop a vaccine against syphilis which is safe and effec-

tive. In part this stems from the unusual nature of the syphilis

bacteria, which remain potentially infectious even when its

cells are killed. An effective gonorrhea vaccine has also

eluded researchers.

Immunizations are available against Hepatitis A and

Hepatitis B (Hepatitis D is prevented by the Hepatitis B vac-

cine). The virus that causes Hepatitis C, however, is able to

change its form (mutate) quite rapidly, thereby hampering

efforts to develop a vaccine against it.

Without vaccinations for most of the sexually transmit-

ted diseases, health officials depend on public information

campaigns to limit the growth of the diseases. Some critics

have claimed that the increasing incidence of sexually trans-

mitted diseases suggest that current techniques are failing. In

other countries, however, the incidence of sexually transmitted

disease has fallen during the same period it has risen in the

womi_S 5/7/03 8:20 AM Page 513