Disease Synergies andHIV Transmission
Linking Millennium Development Goals and HIV
Eileen Stillwaggon
AIDS 2006XVI International AIDS Conference
What drives an epidemic to
40 % prevalencein some countries
and less than 1 % in others?
Median age at first intercourse (selected countries, by gender)
Country Male Female
United States 16 17Great Britain 17 17Haiti 18 19Tanzania 18 17Zimbabwe 19 19
Derived from Singh S, et al. 2000. “Gender Differences in the Timing of First Intercourse: Data from 14 Countries,” International Family Planning Perspectives 26(1):21–28, 43.
Source: John O. G. Billy, Koray Tanfer, William R. Grady, and Daniel H. Klepinger. 1993. “The Sexual Behavior of Men in the United States,” Family Planning Perspectives 25(2):52–60.
23 % of US men report
20 or more female partners
Source: Kathryn Kost and Jacqueline Darroch Forrest. 1992. “American Women’s Sexual Behavior and Exposure to Risk of Sexually Transmitted Diseases,” Family Planning Perspectives 24(6):244–254.
41 % of US women report
4 or more male partners
23 % of US women report
6 + male partners
Source: N. MacDonald, G. Wells, W. Fisher, et al. 1990. “High-Risk STD/HIV Behavior among College Students,” Journal of the American Medical Association 263(23):3155–3159.
Canada: first-year college students
with more than 10 sexual partners
Men: 21 %
Women: 9 %
Source: N. MacDonald, G. Wells, W. Fisher, et al. 1990. “High-Risk STD/HIV Behavior among College Students,” Journal of the American Medical Association 263(23):3155–3159.
Canada: first-year college students
with 5 or more sexual partners
Men: 40 %
Women: 25 %
Genital herpes simplex virus type 2 - seroprevalence, by age,(1976–80) and (1988–94)
Percent
NHANES IINHANES III
0
8
16
24
32
40
Age Group
12-19 20-29 30-39 40-49 50-59 60-69 70+
Note: Bars indicate 95% confidence intervals.
*National Health and Nutrition Examination Survey
Immune system Skin and mucous membranes
– First line of defense Natural Killer cells, macrophages
– Non-adaptive and adaptive immunity B cells
adaptive immunity
T cells
Protein-energy malnutrition
reduces
integrity of skin and mucous membranes
T-cell production
Iron-deficiency anemia
reduces production of
B cells
T cells
Natural Killer (NK) cells
Zinc deficiency
reduces
Natural Killer cell activity
T-cell production
integrity of the skin as a barrier to infection
Vitamin-A deficiency
reduces production of– NK cells– T cells– B cells
reduces skin and mucosal integrity
Vitamin-A deficiency
reduces production of– NK cells– T cells– B cells
reduces skin and mucosal integrity
increases viral load
Maternal malnutrition
increases
mother-to-child transmission
Anemia increases
viral shedding in the birth canal
Global Distribution of Malaria
Malaria
causes chronic immune activation
depresses immune response
Malaria
causes chronic immune activation
depresses immune response
increases HIV replication
increases viral load in people with HIV
Malaria
causes chronic immune activation
depresses immune response
increases HIV replication
increases viral load in people with HIV
increases MTC transmission of HIV
increases sexual transmission of HIV
Malaria
HIV increases malarial parasite load in the
blood, increasing malaria transmission.
Coinfection with malaria contributes to ARV
treatment failure in malaria-endemic areas.
Distribution of Lymphatic Filariasis
Helminths (Worms)
More than 80 % of people in poor communities
have at least one type of worm
Helminths (Worms)
More than 80 % of people in poor communities
have at least one type of worm
Virtually all children in urban slums, shanty towns,
and rural villages have worms
Roundworm, hookworm, whipworm
• infect 25 to 35 % of world population• cause blood loss in intestines• cause anemia• cause Vitamin-A deficiency• cause loss of appetite• increase energy cost
Helminths (Worms)
Roundworm, hookworm, whipworm
• hyperactivate the immune system• depress immune response• increase susceptibility to HIV• increase HIV viral load and
HIV transmission
Helminths (Worms)
00002-E-34 – 1 December 2003
Distribution of Schistosomiasis hematobium
Schistosomiasis (bilharzia)
S. hematobium (urinary schistosomiasis) infects
33 % of Africans, over 200 million people.
Schistosomiasis (bilharzia)
S. hematobium (urinary schistosomiasis) infects
33 % of Africans, over 200 million people.
Causes blood loss, malnutrition, anemia
Schistosomiasis (bilharzia)
S. hematobium (urinary schistosomiasis) infects
33 % of Africans, over 200 million people.
Causes blood loss, malnutrition, anemia
In endemic areas, 75 % of women with urinary
schistosomiasis also have genital infection.
Schistosomiasis (bilharzia)
Worms and ova of S. hematobium infect the vagina,
uterus, vulva, and cervix.
Schistosomiasis (bilharzia)
Worms and ova of S. hematobium infect the vagina,
uterus, vulva, and cervix.
S. hematobium lesions are indistinguishable from STDs
without biopsy.
Schistosomiasis (bilharzia)
Worms and ova of S. hematobium infect the vagina,
uterus, vulva, and cervix.
S. hematobium lesions are indistinguishable from STDs
without biopsy.
Lesions provide direct access to the blood stream for
HIV.
Schistosomiasis (bilharzia)
Worms and ova of S. hematobium infect the vagina,
uterus, vulva, and cervix.
S. hematobium lesions are indistinguishable from STDs
without biopsy.
Lesions provide direct access to the blood stream for
HIV.
Worms and ova produce inflammation, attracting CD 4+
cells to the cervix and other sites in the reproductive
tract.
00002-E-45 – 1 December 2003
S. hematobium in Tanzania
S. hematobium in South Africa and Swaziland
What is causing the epidemic of HIV/AIDS?
I = N x P x T
where I is probability of sexual infection,
N is the number of partners,
P is the prevalence rate in the population, and
T is the per-contact transmission risk, which is assumed to be the same for every population.
One risk fits all.
I = N x P x T
T = V – + C + (or T = V – x C +)
risk of transmission = vulnerability + contagiousness
V – = f {standard risk, H, M, F, TB, STD, SCH, . . . }
C + = g {standard risk, H+, M+, F+, TB+, STD+,
SCH+, . . . }
AIDS is aDevelopment Issue