EPIDEMIOLOGY OF HIV/AIDS

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DR. PROSPER OKONKWO

OUTLINE

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• Brief History and Current Epidemiology: Global and Nigeria
• Natural History of HIV
• Transmission of HIV
• Factors driving the epidemic
• Prevention of HIV transmission
• Global impact of HIV
• Recent development in HIV/AIDS policy and guidelines

EPIDEMIOLOGY 101

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Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems.

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EPIDEMIOLOGY 101

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Epidemiology is the study (scientific, systematic, data-driven) of the distribution (frequency, pattern) and determinants (causes, risk factors) of health-related states and events (not just diseases) in specified populations (patient is the community, individuals viewed collectively), and the application of this study to the control of health problems.

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INTRODUCTION

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• Not clear how many people were infected with HIV or developed AIDS before the early 1980s.

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• In 1981, cases of very rare lung diseases were found in five young previously healthy gay men in Los Angeles.

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• At the same time, cases of unusually severe among a group of men in New York were reported.

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• Later the same year, the first cases of these lung diseases were reported among people who inject drugs

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• By the end of that year, about 270 cases of severe immune deficiency among gay men were reported, leading to more than 120 deaths.

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• Studies suggested that sexual, blood transfusion, and injecting drugs as routes of transmission.

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INTRODUCTION

• CDC first used the term AIDS to describe the disease in 1982.

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• Later AIDS was reported amongst female partners of positive men, suggesting it could be passed on through heterosexual routes.

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• The virus that caused AIDS was discovered in France in 1983, first called Lymphadenopathy-Associated Virus (LAV), and later in 1986, Human Immunodeficiency Virus (HIV)

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• Mother to Child transmission was also recognized as a route for infecting unborn children

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• Casual contacts, food, air, and water were excluded as usual routes of transmission

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• Over the years, increasingly more sensitive and effective reagents and drugs have been developed, making diagnosis easier, and AIDS now regarded as a chronic disease

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INTRODUCTION

• The Human Immunodeficiency Virus (HIV) {INFECTION} is the cause of the spectrum of disease known as AIDS. {DISEASE}

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• HIV is of the retrovirus class of viruses that primarily infects components of the human immune system such as CD4⁺ T cells, macrophages, and dendritic cells. It, directly and indirectly, destroys CD4⁺ T cells

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• Two types of HIV have been characterized: HIV-1 and HIV-2.

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• HIV-1 is the predominant and first described virus.

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• In contrast, HIV 2 is mostly found in West Africa and accounts for less than 1% of infections worldwide

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BRIEF HISTORY-GLOBAL

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• 1981- Recognition of the syndrome in USA and Europe- First among gay men

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• 1983-5- Discovery of HIV-1 and development of ELISA test, recognition of the disease in Africa and the Caribbean

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• First decade (1985-1995)- Learning about the disease as it spread

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• Second decade (1995-2005)- Failure of both behavioral change and vaccine development

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• Third decade (2005 till date) – Scale-up of treatment and evidence of factors leading to successful prevention

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BRIEF HISTORY-NIGERIA

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• The first two cases in Nigeria were diagnosed in Lagos in 1985

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• One of the first two cases was a young female teenager aged 13 years from one of the West African Countries

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• The Nigerian public received the news of the presence of AIDS in the country with doubt and disbelief.

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• AIDS was then perceived as the disease of a distant land that had no place in Nigerian society as the first case was from a foreigner.

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CURRENT EPIDEMIOLOGY (2020)

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• 37.6 million people globally were living with HIV

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• 1.5 million people became newly infected with HIV

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• 690 000 people died from AIDS-related illnesses

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• 27.4 million people were accessing antiretroviral therapy

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• 77.5 million people have become infected with HIV since the start of the epidemic.

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• 34.7 million people have died from AIDS-related illnesses since the start of the epidemic.

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CURRENT EPIDEMIOLOGY (2020)

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• 84% of people living with HIV knew their HIV status.
• Among people who knew their status, 87% were accessing treatment.
• And among people accessing treatment, 90% were virally suppressed.
• Of all people living with HIV, 84% knew their status
• 73% were accessing treatment
• 66% were virally suppressed in 2020.

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GLOBAL PICTURE: 38 MILLION LIVING WITH HIV-2020

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Distribution of acquisition of new HIV infections by population, global, sub-Saharan Africa and rest of the world, 2021

BACKGROUND

NAIIS 2018, IBBSS 2020, UNAIDS Spectrum estimates 2022, Nigeria Spectrum estimates 2022

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NIGERIA HIV PREVALENCE

HIV PREVALENCE BY STATES (NAIIS 2018)

EPIDEMIOLOGY-NIGERIA (2021-22)

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HIV PREVALENCE BY GEOPOLITICAL ZONES (NAIIS 2018)

HIV PREVALENCE BY AGE AND SEX (NAIIS 2018)

HIV PREVALENCE TREND- URBAN VS. RURAL

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HIV PREVALENCE IN NIGERIA

• HIV prevalence is dropping in the general population at 1.4% but is still high among key populations

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• Various key populations (KP) including Female Sex workers (FSW), Men who have sex with Men (MSM), and People who Inject Drugs (PWID) make up only 3.4% of the population, yet account for around 32% of new HIV infections

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• Globally, Key populations account for less than 5% of the global population, but they and their sexual partners comprised 70% of new HIV infections in 2021

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• MSM -25%
• Sex Workers-15.5%
• PWID-10.9%
• Transgender-29%

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ART TREATMENT COVERAGE IN NIGERIA

THE HIV VIRUS

AGENT OF INFECTION

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• The Human Immunodeficiency Virus (HIV) is the cause of the spectrum of diseases known as HIV/AIDS.

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• HIV is a retrovirus that primarily infects components of the human immune system such as CD4⁺ T cells, macrophages, and dendritic cells. It, directly and indirectly, destroys CD4⁺ T cells

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• HIV is a member of the genus Lentivirus, part of the family Retroviridae

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• Two types of HIV have been characterized: HIV-1 and HIV-2. HIV-1 is the predominant and first described virus.

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AGENT OF INFECTION

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• Two HIV viruses are currently involved in the global HIV pandemic – HIV 1 and HIV 2

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• HIV 1 has been found in almost every country around the world since its discovery in 1983. Several sub-types, called clades (A-F) have now been recognized

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• The geographic mapping of the clades isolated from various parts of the world has revealed that certain clades are solely prevalent in certain regions while several others may coexist in other regions**

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AGENT OF INFECTION

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• In contrast, HIV 2 is mostly found in West Africa and in countries that are linked to this region through population movements. It accounts for less than 1% of infections worldwide

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• There are structural, serological, and pathogenic differences between HIV1 and 2. Epidemiological studies have also shown that HIV1 transmits more efficiently than HIV2

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• In areas where HIV2 was the major cause of infections when it was first recognized in 1986, the spread is being overtaken by HIV1

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AGENT OF INFECTION

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• HIV-2 is less easily transmitted
• HIV-2 develops more slowly
• MTCT is relatively rare with HIV-2

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• Note similarities
• Transmitted through the same routes
• Associated with similar opportunistic infections

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GENETIC DIVERSITY OF THE VIRUS

IMPORTANT DEFINITIONS

• Window period. The time between when a person is infected with HIV and wan hen antibody test is positive

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• Antibodies usually develop in infected people between 4 to 6 weeks but may take as long as 3 months to be detectable. Retest if high index of suspicion

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• Asymptomatic HIV infection. Occurs in a person who is HIV infected but looks and feels healthy

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• Symptomatic HIV infection. Occurs in a person who has developed physical signs of HIV

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• Opportunistic infections. Illnesses caused by a germ that might not otherwise cause illness in a healthy person, but will in persons with a weakened immune system

NATURAL HISTORY OF HIV

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• Natural history relates to the possible course a disease would take if no interventions like treatment are instituted

• Virus can be transmitted during each stage

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• Seroconversion. Infection with HIV and antibody development

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• Asymptomatic. No signs yet of HIV. The immune system controls virus production

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• Symptomatic. Physical signs of HIV infection with some immune suppression

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• AIDS. Opportunistic infections and end-stage disease.

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NATURAL HISTORY OF HIV

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• Immune Suppression

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• The Virus attacks white blood cells (CD4 cells) that are protective

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• Over time, the body loses its immune defence system

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• Opportunistic Infections then occur

NATURAL HISTORY OF HIV

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HIV TRANSMISSION

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• Sexual
• Vaginal (99% of sexual transmission)
• Anal
• Oral sex
• Parenterally
• Transfusion of infected blood/blood products
• Donated organs
• Unsterilized needles

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HIV TRANSMISSION

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• Perinatally- Mother to Child Transmission (MTCT) occurs:
• During pregnancy
• Labor and delivery
• Breastfeeding
• Occupational Transmission
• Healthcare workers
• Laboratory staff

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PERINATAL TRANSMISSION

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• Perinatal transmission accounts for about 90% of pediatric infections

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• 20% in utero

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• 60-65% at delivery

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• 12-15% via breast milk

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• 25-40% transmission in the absence of intervention in SSA.

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PERINATAL TRANSMISSION

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• Perinatal transmission accounts for about 90% of pediatric infections

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• 20% in utero

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• 60-65% at delivery

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• 12-15% via breast milk

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• 25-40% transmission in the absence of intervention in SSA.

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• Breast feeding

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• Cost

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• Ignorance

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• Stigma and family pressure

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• Clean water argument

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• Anti Retroviral drugs

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DRIVERS OF HIV EPIDEMIC IN NIGERIA

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• Low personal risk perception.

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• Multiple concurrent sexual partnerships

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• Transactional and intergenerational sex

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• Sexual transmission among key populations (MSM, Brothel based FSW, and Non-brothel based FSW)

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• Sexually transmitted diseases (genital ulcers and Non-ulcerative STIs)

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DRIVERS OF THE HIV EPIDEMIC

• Poor health care delivery system.

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• Stigma and discrimination

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• Socio-economic factors

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• Cultural factors:
• Early marriage
• Widowhood rite and widow inheritance
• Polygamy, polyandry, and concubinage

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MANAGEMENT

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• Diagnosis
• Clinical (Staging no longer very useful-Test and Treat)
• Laboratory
• Prevention
• Care
• Laboratory monitoring
• Opportunistic Infections
• Treatment (Pre/Post-exposure prophylaxis, ART Therapy, TasP)

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PREVENTION

• Combination prevention. Simultaneous employment of different approaches and intervention types for the prevention of HIV infection. Minimum Prevention Package intervention (MPPI) combines a set of approaches

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• Biomedical approach (Clinic and community-based approaches to reducing exposure and risk of transmission and infection. Examples)

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• Behavioural approach (Behaviour Change Communication). The gap between knowledge and behaviour is a challenge

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• Structural approach. Targets social, legal, political and economic factors that increase vulnerability to HIV

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• Best Results are achieved when all the methods are combined in some measure

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PREVENTION

• Combination prevention. Simultaneous employment of different approaches and intervention types for the prevention of HIV infection. Minimum Prevention Package intervention (MPPI) combines a set of approaches

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• Biomedical approach

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• Behavioural approach

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• Structural approach

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PREVENTION- BIOLOGICAL APPROACH

These interventions are targeted at the individual level through community outreach and clinic-based activities to reduce HIV exposure, transmission, and or infection.

Examples:

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• HTS, STI screening and treatment, condom distribution and other clinical services (e.g. TB screening and linkage to care), voluntary medical male circumcision (VMMC), antiretroviral therapy (ART) for Treatment, pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP), OI medications.

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• PMTCT

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PREVENTION- BEHAVIORAL APPROACH

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• Include a range of behaviour change communication activities designed to promote HIV risk-reducing and protective behaviours

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• These activities span and often combine mass media, community mobilization, advocacy and interpersonal communication (IPC) such as one-to-one or one-to-group educational activities and community meetings.

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• Knowledge – Behaviour gap

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PREVENTION- STRUCTURAL APPROACH

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• These are strategies recommended for change in social, legal, political, and economic factors that increase vulnerability to HIV.

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• These interventions address stigma and discrimination, gender-based violence, policy issues affecting key populations, individual empowerment issues, and inequality.

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RECENT DEVELOPMENTS

• The role of ART- Treatment and Prevention

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• A recognition that we have tools not only to prevent HIV but theoretically to stem and even stop the epidemic

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• WHO/UNAIDS have set a global target of reducing HIV transmission by 50% by 2020 and eliminating HIV by 2030

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• National HIV/AIDS Policies are always under review to keep pace with global changes

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• Strategic Plans accompany these policies to operationalize new directions.

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RECENT CHANGES IN HIV CARE AND TREATMENT

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• Test and start
• A progression over the past 10 years from CD4 200 ˗ CD4 350 ˗ >CD4 500 as the threshold for initiating treatment
• Now anyone who has HIV should be initiated on treatment

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• 90-90-90 UNAIDS goal for 2020
• 90% of PLHIV should their status
• 90% of HIV+ put on ART
• 90% of people on treatment have viral suppression

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• Goal is 95-95-95 by 2030

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• Using data to ensure targeted programming

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THE FUTURE

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• Vaccine

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• Cure

GLOBAL IMPACT OF HIV

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• Negative Economic Impact

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• Impact on health systems-Negative and Positive

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• Reversal of gains of childhood survival

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• Increasing Orphan Population

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• Decreasing life Expectancy

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REFERENCES

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• UNAIDS epidemiology fact sheets

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• Lawrence Gelmon: HIV/AIDS in the World 2017: Epidemiology and Issues

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• AIDS in Africa: Epidemiology of HIV (Currently under review)

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