"Genital infection with HPV is one of the most common
sexually transmitted diseases, with its prevalence in young women
ranging from 20 percent to 46 percent in different countries," says
Study Director Robert D. Burk, M.D., of the Department of Pediatrics,
Microbiology and Immunology, and the Department of Epidemiology
and Social Medicine at the Albert Einstein College of Medicine. "The
public health impact of this infection is compounded by the
recognized causal relationship between genital infections with certain
types of HPV and cell abnormalities of the cervix and cervical cancer."
"The incidence of HPV infection in sexually active young
college women is alarming. Furthermore, we currently have no
effective way to prevent infection. The need for topical microbicides
and effective vaccines is urgent," says Penny Hitchcock, D.V.M., chief
of the sexually transmitted diseases branch in NIAID's Division of
Microbiology and Infectious Diseases. "It is certainly reassuring that
only a small number of women will develop cervical cell changes or
cancer. However, until we have more precise diagnostic tests, it is
important for young women to have regular Pap smears."
Through campus-wide advertisements at a state university in
New Brunswick, N.J., the study team enrolled 608 young women.
Their average age was 20 years, and the ethnic distribution was 57
percent white, 13 percent Hispanic, 12 percent black and 18 percent
other. Twenty-six percent were diagnosed with HPV infection at the
beginning of the study. Each of the women had pelvic examinations
and Pap smears at the study outset and annually. For a maximum of
three years, the women responded at six-month intervals to
questionnaires on lifestyle and sexual behavior. At the same visits,
samples of cells from the cervix and vagina were taken to ascertain
whether or not HPV was present and to determine the type, or strain,
of HPV. If the same type of HPV was present during two consecutive
visits, the infection was defined as persistent. The average duration
of HPV infection was eight months.
The cumulative incidence of HPV infection in the women who
were HPV-negative at baseline was 43 percent. The investigators
noted, however, that this incidence decreased with time: it was 20
percent in the first 12 months; 14 percent in the second 12 months;
and only 9 percent in the final 12 months.
"The encouraging news," says Dr. Hitchcock, "is that this study
suggests that the body's response to infection plays an important role
in limiting persistence of the virus and disease progression. If this
is mediated by the immune response, it could indicate that development
of prophylactic and therapeutic vaccines would play an important role
in prevention and control."
Higher risk and incidence of HPV infection are associated with
younger age, ethnic minority subgroups, increased frequency of
alcohol consumption, anal sex or a high frequency of vaginal sex. A
woman was less likely to have an HPV infection last for six months if
it had been her first infection. The longer an infection endured from
previous visits, the more likely it was to persist.
One of the consequences of HPV infection is the presence of
various types of abnormal cells. One such type, squamous
intraepithelial lesion, a potentially pre-cancerous condition, is caused
by HPV infection of cervical cells, and is usually first detected as an
abnormal Pap smear.
The authors caution that because of the six-month interval
between medical visits, the study results may underestimate the
incidence and overestimate the duration of HPV infection. They also
warn that it is uncertain whether these data apply to older women.
In addition to Dr. Burk, collaborators included Gloria Y. F. Yo,
Ph.D., and Chee J. Chang, Ph.D., both of the Albert Einstein College
of Medicine, Bronx, N.Y.; and Robert Bierman, M.D., and Leah
Beardsley, N.P., both of Rutgers University Student Health Service,
New Brunswick, N.J.
NIAID, part of the National Institutes of Health (NIH), supports
biomedical research to prevent, diagnose and treat illnesses such as
AIDS, tuberculosis, malaria, asthma and allergies. NIH is an agency
of the U.S. Department of Health and Human Services.
Press releases, fact sheets and other NIAID-related materials are
available via the NIAID Web site at http://www.niaid.nih.gov.