Emerging Infections of International Public Health Importance
Carrie Horwitch, MD, MPH
I’m going to give you a brief overview of the current HIV/AIDS epidemiology. It is particularly interesting to me that this is a disease that is not that easy to acquire. It requires very close contact, either through sexual contact or blood, and yet in 25 years this has circumnavigated the world and is one of the top five infectious diseases worldwide causing a significant amount of morbidity and death.
UNAIDS map of global HIV/AIDS cases from 2001.
The total number affected is an estimate and could be as high as 44-46 million worldwide. The largest burden of disease is in sub-Saharan Africa but the rates are growing in Southeast Asia.
There is an increase of HIV/AIDS cases annually of 5.3 million; of these, 2.3 million are in women and 570,000 cases are in children. There are 16,000 new cases and 8,000 deaths daily worldwide. More than 95% of these cases are in developing countries. Seventy-five percent are in ages 15-49 years and 50% of cases are in women. Since 1981, over 22 million people have died from diseases related to AIDS. Currently there are an estimated 13 million orphans.
In the United States there are close to 1 million cases. Since the early 1980’s there have been almost ½ million deaths. Annually we have 40,000 new cases. The positive news, however, is that since 1995 the annual mortality from HIV/AIDS has decreased by 75% in large part due to better treatment options with antiretroviral medications and prevention of opportunistic infections. Vertical transmission rates have been reduced to less than 2% by use of antiretroviral therapy.
This chart shows that persons of color are disproportionately affected.
This chart shows an increase in cases among women.
A similar chart from years earlier would show that women only accounted for approximately 10% of the HIV/AIDS cases. This is a huge increase over the past decade.
In Washington State, we have approximately 9700 cases. There are 400-500 new cases annually. The majority of these cases are seen in younger population, MSM (men who have sex with men) and heterosexual people of color. Death from HIV/AIDS has also declined in King County.
Factors of Emergence
The primary factors that influence emergence and spread of HIV are:
Technology and trade factor is responsible for transmission of HIV virus into South America through contaminated Factor VIII used as a treatment for hemophilia. Once in a country it is spread through the usual means: sex and blood transmission. Since the HIV virus has been identified, the blood and blood factor supply in the United States has been virus free. Other countries however, do not all screen their blood so globally this is still a concerning method of transmission.
Human demographics and behavior has clearly played the largest role on continuing spread of this virus and is the main route of heterosexual spread both by sexual contact and IV drug use. Efforts to change behavior have not had great success at prevention or control of this disease to date. Also women are at significant risk of disease acquisition since in many places of the world women do not have protected rights or the ability to prevent unwanted sexual contact even at very young ages. The modes of transmission for HIV/AIDS includes unprotected sexual contact, contaminated needle exposure (i.e IVDU, needle sticks among health care workers), vertical transmission (mother to child), breast feeding, and contaminated blood products.
This chart again shows the increase in heterosexual transmission in the US.
Modern travel has made the spread of this virus much faster and easier in recent years. Both air travel and spread of HIV along trucking routes has been documented. Due to the long length of time for HIV infection to become clinically apparent, the disease can spread quite widely.
Breakdown of public health has been a problem due to lack of control methods being put into place quickly and effectively. Likewise, financial support for chronic communicable diseases is lacking in the US and certainly more so in the developing world.
Political will has assisted in control of the disease where the government has taken strong steps to prevent the transmission through education and barrier protection campaigns. However, political will has also been detrimental in countries where political leaders have denied existence of HIV/AIDS, refused to take action to reduce the continued spread, neglected to promote less risky behavior, or not embraced fully the treatment of infected people. These political battles are still being fought in many countries and we will continue to see large populations be affected for their decisions.
HIV as an economic and security threat
Why is HIV a potential, economic and security threat around the world? First, let’s look at the characteristics of the disease. HIV is a chronic viral infection with no cure and requires treatment that is difficult, expensive and needs to be continued over time to be effective. HIV primarily affects the T-lymphocytes that help protect the body against opportunistic and atypical infections. When these T-lymphocytes are destroyed it leaves a person vulnerable to multiple different infections, many of which are life threatening. Over time, and without treatment, HIV disease progresses and ultimately leads to death. This process can be a few years or can be prolonged over a longer period of time. However, the disease primarily affects younger persons who are the major work source in the world and the women are usually in their child bearing years.
The gravest threat to human security stems from the dismantling of existing health, education and welfare systems in industrialized societies. Globally, in countries less industrialized, there is concern for further destabilization of the economy as workers become too sick to work their jobs. Money has to be spent for health care instead of boosting the economy. Also, the military is severely affected as many of the people infected are at the age of entering into the military; therefore, HIV/AIDS can affect not only the economy but also the security of a country. This issue was so concerning that in June 2001, the first UN General Assembly special session was on HIV/AIDS. In this session the following goal was outlined:
By 2003, enact, strengthen or enforce legislation and regulations to eliminate discrimination against those living with HIV and ensure full human rights and freedoms including access to education, employment, health care, and social services. These goals were established to maintain privacy and combat stigma.
Sadly, it is now almost 2005 and none of the goals of the special session have been met.
In 1999, the sub-Saharan Africa’s GDP was $324 billion, of which South Africa produced 1/3 of the total GDP. Economic models have shown that South African growth would decline by 0.4% annually due to HIV/AIDS alone. Studies are being conducted to look at HIV costs to businesses. Preliminarily, the “AIDS tax” (HIV directly costing businesses) is approximately 2-8% of the annual salaries.
This is a chart of various studies that have been completed over the past two decades, an attempt to assess the economic impact of HIV on various economies.
In the left column are the studies and the year, second column are the countries involved in the study, the third column is the HIV data year, and the last column is the economic result (increase or decrease) based on HIV disease. As you can see, much of the data is based on older HIV statistics in the countries and these numbers have all increased over the past decade.
Other economic effects include a reduced labor supply. One study of South African mining showed that currently 60% of the mining work force is in the 30-44 year age range. In 15 years, they are predicting that only 10% of the work force will be in this age range due to HIV/AIDS infection.
Reduced labor productivity with more sick days and less productive days will decrease business net output and profit. Reduced exports and increased imports will occur, as less domestic productivity will mean more need to imported goods, including food. There will also be a need for increase in healthcare goods. There will be increased health care costs to businesses, both in direct costs for paying of medical care, treatment, and hospitalization, and in indirect terms of productivity lost to do sick days.
WHO 3 x 5 Initiative
Based on the rising concern for health, economic and security issues with HIV/AIDS, the WHO has established the 3 x 5 initiative as one answer to this crisis. The initiative goal is to treat 3 million people with HIV and who are eligible for highly active antiretroviral therapy (HAART) be placed on medication by the end of 2005.
The campaign elements of the 3x5 initiative are:
The key elements to 3 x 5 initiative are:
What are the benefits of HAART therapy?
This graph shows the estimated incidence of AIDS and deaths of adults/adolescents with AIDS, 1985-1999, in the US.
This shows that the death rates were already starting to decline even before HAART therapy had widespread use in 1996. Part of this decline was due to the better understanding of the disease and using therapy to prevent opportunistic infections such as Pneumocystis pneumonia.
HIV disease and care requires initial and continual assessment over time, whether on medication or not. The goal of monitoring is to determine the best time to start antiretroviral therapy. Regular visits for history, physical, symptom review and lab assessment are necessary. WHO staging criteria are used to determine when to start patients on HAART therapy. Baseline laboratory studies including hematocrit, t-cell count (CD4), and liver tests are all needed for starting therapy, reducing toxicity of medication and changing therapy.
Other needs for the 3 x 5 initiative that are currently missing:
Current need for treatment and availability
Currently, based on WHO guidelines, persons with clinical AIDS (WHO Stage 4); advanced (WHO Stage 3); pregnant women with HIV; WHO Stage 2 or 3 with total lymphocyte count <1200; and WHO stage1, 2, or 3 with known CD4 count <200 are all eligible for antiretroviral therapy.
This slide shows the map of world showing percentages of people who are currently covered for HAART and where the current needs for medicine are.
The areas of largest need for medication are where the disease problem is also greatest (sub-Saharan Africa and Southeast Asia). In Africa alone, approximately 4.5 million people are eligible for treatment. Their coverage rate is only 2% compared with 84% coverage in the Americas.
This table shows how many are currently treated, the number needing treatment and the percent of persons covered in the general regions of the world.
You can see the major need is in Africa and Asia, but only 9% currently have coverage. Worldwide only 400,000 people are on treatment when more than 5.9 million people should be on treatment.
The current resources needed for control are estimated to be 8-9 billion dollars annually. The estimated cost of HAART for the 3 x 5 initiative is US $5.5 billion by 2005; only a fraction of that amount has so far been spent from the US for this initiative. The average cost for essential interventions would be only $34 per person per year. Some economists have estimated that the benefit globally by 2020 would be a savings of $360 billion dollars. (Source: Commission on Macroeconomics and Health). This effort is possible if we choose to put our resources into this endeavor.
Prevention and Control for HIV/AIDS
One thing to remember is that HIV is a preventable disease. Several methods have been tested and found to be effective at reducing HIV risk and transmission of disease:
Prevention successes have been seen in a few countries in the world. Many were successful because the respective governments and their political will made recommendations and backed them up.
For example, Thailand instituted a “condom campaign” in the commercial sex worker industry and were able to decrease infection rates from 4% to < 1%. They insisted on 100% condom use in this industry; the burden is on the customer coming for service and it makes it safe for a CSW (commercial sex worker) to refuse service if no condom is used. This strategy is still being utilized today.
Tanzania was able to decrease their HIV incidence by 38% by doing sexually transmitted disease syndromic surveillance. Treating other STDS has been shown to be effective at reducing HIV transmission as well.
Uganda has used the ABC or D (abstinence, be faithful, use condoms or die) approach and has reduced new infection rates from 30% to approximately 5%. They have also been concentrating on reducing stigma from the disease and promoting counseling and testing.
Brazil decreased transmission among pregnant women by applying the prevention of mother-to-child transmission (pMTCT) program with the use of single dose antiretroviral therapy. They have also implemented active treatment and harm reduction programs in vulnerable populations.
Prevention of mother to child transmission has been a success story. The ACTG 076 study using AZT showed a 2/3 reduction of vertical transmission in mothers who took the drug before delivery compared to no drug. This has led to widespread pMTCT using either AZT or nevirapine before delivery (during labor) and treating the newborn immediately. When HAART is used, we can reduce transmission to less than 2%.
Post exposure prophylaxis studies show the average risk of infection from percutaneous exposure among health care workers (HCW) to be 0.3% (0.09% for mucous membrane exposure). Retrospective case control studies have shown an average of 81% reduction in HIV transmission in HCWs who had exposure and took short term HAART treatment.
HIV treatment as a prevention strategy: The theory is if we lower the viral load then there is likely less transmission of the virus and less drug resistance. We have data that shows that treatment of HIV can improve outcomes for tuberculosis, which is a major cause of death around the world. Treatment also gives people hope and can reduce stigma and encourage more testing.
Future of HIV prevention and care
In summary, HIV/AIDS is one of the top five infectious diseases worldwide. It impacts individuals, families, communities, economies and security. Treatment initiatives have been started and can be achieved given enough funds and resources. Prevention strategies must be emphasized and given government backing and support. We have the capability to stem the rise of this disease and reverse the trends but it will take a lot of effort and resources.