Disease Synergies and HIV Transmission Linking Millennium Development Goals and HIV

transcript

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

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

increases HIV replication

increases viral load in people with HIV

Malaria

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.

Causes blood loss, malnutrition, anemia

In endemic areas, 75 % of women with urinary

schistosomiasis also have genital infection.

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

without biopsy.

Lesions provide direct access to the blood stream for

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

Disease Synergies and HIV Transmission Linking Millennium Development Goals and HIV

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