University of California, San Francisco researchers and Brazilian colleagues
report that analysis of blood samples taken at an anonymous test site in
Santos, Brazil from 1995 to 1999 show an increase in the rate of HIV infection
after a period of decline.
The increase was noted particularly in heterosexual women, a group that has not
previously had a high rate of HIV infection in this area.
A preliminary analysis of a small number of blood samples also found evidence
of transmission of a drug-resistant virus strain, said Kimberly Page-Shafer,
PhD, MPH, UCSF assistant professor of medicine and epidemiologist with the UCSF
Center for AIDS Prevention Studies.
Page-Shafer presented the findings today (July 13) at the XIII International
AIDS Conference in Durban, South Africa.
The port city of Santos has been an epicenter of the AIDS epidemic in Brazil,
and offers an excellent system of testing and treatment, according to
Page-Shafer. Previous analysis of the epidemic had shown a high rate of HIV
infection in men who have sex with men and in IV drug users, and well directed
education and prevention efforts have been targeted at these groups.
In Santos, and throughout Brazil, antiretroviral treatment is available free of
charge to anyone who is HIV positive, said Page-Shafer.
“The widespread availability of antiretroviral therapy has been a tremendous
public health service to the population. At the same time, however, there has
been some concern that inadequate adherence to medications might lead to the
development of drug-resistant viral strains,” said Page-Shafer.
The study used a new test, developed at the Blood Centers of the Pacific in San
Francisco and the Centers for Disease Control and Prevention (CDC), that can
distinguish recent infections from long-standing ones. It allows researchers to
identify individuals who have become infected within the past 4 to 6 months.
This study is one of the first applications of this sensitive test to
surveillance activities outside of the United States.
“The new test is very valuable because surveillance and prevention have been
difficult without a way to distinguish recent infections. This test provides a
tool that allows us to precisely identify where transmission is occurring now,
and target prevention efforts accordingly,” said Page-Shafer.
Researchers used the test on HIV-positive frozen blood samples drawn at an
anonymous counseling and testing site in Santos for the four-year period
1995-99. Of 392 HIV positive frozen samples, 44 (11 percent) were found to be
The researchers then looked more closely at the 18 recent infections that
occurred in 1999. In this group, 76 percent were women, most of whom reported
one sex partner within the past year. Recently infected individuals were also
more likely to report anal sex and a history of sexually transmitted disease.
Overall, the researchers calculated the annual incidence of HIV infection
(number of new cases per 100 people per year) to be 1.9 percent in 1995, 1.5
percent in 1996, 1.3 percent in 1997, 2.4 percent in 1998, and 3.2 percent in
“The increase in the rate of HIV infection in the last two years of the study
is cause for concern,” said Page-Shafer.
Researchers are still in the process of analyzing a small number of
recent-infection blood samples to see if the virus they contain is resistant to
antiviral drugs. So far, they have found one of five samples to be resistant to
“The evidence of transmission of antiretroviral-resistant virus points strongly
to the need for further efforts to monitor this phenomenon in Brazil,” said
Research co-investigators included Katia Alves, MD, infectious disease
specialist and Fogarty Fellow at UC Berkeley and the Blood Centers of the
Pacific; Bhupat Rawal, PhD, also from the Blood Centers of the Pacific; Marcos
Caseiro, MD, director of the Central AIDS Clinic (CRAIDS)in Santos, Brazil, who
is associated with Federal University of San Paulo (UNIFESP); Ricardo Diaz, MD,
director of the Retrovirology Laboratory at UNIFESP; Cecilia Sucupira, a
research scientist at UNIFESP; Hugo Guevara, PhD, and Mike Hendry, PhD,
microbiologists with the Department of Health Sciences Viral and Ricketssial
Disease Laboratory; Alison Graves, MPH, research assistant with the UCSF Center
for AIDS Prevention Studies (CAPS); George Rutherford, MD, director of the CAPS
International Program; and Thomas J. Coates, PhD, executive director of the
UCSF AIDS Research Institute and CAPS.