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In times of significant change there are often many hard questions to answer. In the case of HIV, the footprints to public health understanding begin in epidemiologyThe branch of medical science that deals with the study of incidence and distribution and control of a disease in a population..

Epidemiology is about the scientific study of epidemics. I like to think of epidemiology as the backbone or skeleton from which the organs, heart, circulatory and nervous systems are all added before the flesh finally fills and gives form to a body of scientific knowledge – with a backbone and skeletal structure that ‘shape changes’ given the right set of conditions or in response to certain interventions.

Understanding what drives HIV transmission or progression, and projecting its path under different scenarios is the business of epidemiology. It uses a range of methods (from observation to randomisedA method based on chance by which study participants are assigned to a treatment group. Randomization minimizes the differences among groups by equally distributing people with particular characteristics among all the trial arms. The researchers do not know which treatment is better. From what is known at the time, any one of the treatments chosen could be of benefit to the participant clinical trials) to scientifically classify and identify facts that help us to understand what’s going on and to see what’s responsible for particular health problems or disease.

It is exactly these skills that make epidemiology the science of public health – as public health is about health protection (regulations), illness prevention (reducing new infections and disease), and heath promotion (empowered health improvements) with the development of support infrastructure (building blocks).

For example before we knew AIDS was caused by a virusA small infective organism which is incapable of reproducing outside a host cell. (HIV), AIDS was understood through a range of factors that affected some people who got very sick after their immune systems were weakened. But it wasn’t known at that stage what particular weight to give to genetic, environmental or behavioural factors in seeking ways to respond to the challenge of AIDS. After HIV was identified and over time using epidemiological methods, it was discovered that HIV could be avoided by changing behaviour - that it wasn’t something inherited or something environmental that only affected gay men or blacks living in sub Saharan Africa.

Public health responses need these methods and tools to anticipate risks and prevent problems associated with disease and illness.

Tools of the trade

Like any skilled tradesperson, epidemiologist need to use their tools wisely and for the task at hand – and like any trade, the methods and tools in use today have developed to meet the challenges of our complex evolving world where communication and understanding the relevance of connections is imperative to planning future public health services.

Let me briefly outline the main ways:

Surveillance

It all starts with observation, collating raw numbers and percentages - how many people are there – living, with AIDS, who have died or how many times this or that was done to whom and where – it’s raw information collected through observation.

Data linkage

Whether it’s by analysing particular cases to understand rare conditions or particular cohorts of individuals exposed to risks, data linkage starts with the questioning and analysis that explores the connectionsof the past to the present. Examples would be the way that AIDS was originally understood through clusters of disease impacts, or the ways that studying sexual behaviour informs present understandings of HIV transmission risks.

Ethical experiment

Regarded by most as the gold standard and by me as the ‘ghost buster’ tool is the randomised clinicalPertaining to or founded on observation and treatment of participants, as distinguished from theoretical or basic science. trial (rct). Through the rct a particular hypothesisA supposition or assumption advanced as a basis for reasoning or argument, or as a guide to experimental investigation. is tested and hopefully proven or not. Examples of the rct include therapeutic or preventative interventions such as giving half of the participants in a rct a new disease treatment and the other half the current best practice treatment hoping to improve outcomes and change disease. As we’re talking trials in humans here, it’s governed by ethics(In clinical trials) The process of determining that a proposed clinical trial conforms to a wide range of moral, scientific and ethical standards, to ensure that participants in the trial are not abused, mistreated or unfairly taken advantage of. Before a clinical trial can go ahead, it must be given approval via an independent ethics process. and ‘do no harm’.

Enhancing efficacy(Of a drug or treatment). The maximum ability of a drug or treatment to produce a result regardless of dosage. A drug passes efficacy trials if it is effective at the dose tested and against the illness for which it is prescribed. In the standard procedure, Phase II clinical trials gauge efficacy, and Phase III trials confirm it. through evidenced practice – clinical epidemiology

Applying learning about the nature and quality of evidence used to guide clinical decision- making in enhancing the efficacy of treatment regimens. Further enhancements to public health practice now include the strategic use of public health nurses to enhance the quality use of medicines.

Molecular and genetic epidemiology

Relatively recent advances in bioengineering, biotechnology and biotech medicines have taken epidemiology to the realms of the molecular and genetic.

HIV treatments are now highly engineered molecular site-specific biotech drugs. As HIV replicates itself and its genetic material, the process involves many genetic replication errors – resulting in HIV mutants. The mutant is not as ‘fit’ or replication competent as the original or wild type virus and so in most situations where people have fully suppressive HIV treatments, the mutant presents no serious threat.

But as we know, in the presence of HIV treatments, sometimes due to adherence difficulties and missing doses, HIV replication leads to the development of HIV treatment resistance. Of course this is not the only reason for the development of HIV resistance.

What’s important to understand in this context of HIV epidemiology is that the HIV virus is evolving even in the context of effective and suppressive HIV treatments. Without suppressive HIV treatments and in the context of poor adherence, the risk is that HIV can evolve and cause deadly harm – a situation familiar to the crisis days of HIV management.

One challenge for HIV epidemiology today is to integrate our genetic knowledge through understanding the development of resistantHIV which has mutated and is less susceptible to the effects of one or more anti-HIV drugs is said to be resistant. HIV and use this knowledge wisely to inform necessary public health responses. Fortunately for public health responses, genetic technology has developed new assay capacities – firstly to test quickly for HIV (using Rapid HIV testing) with accuracy and, secondly, the capacity to test HIV to see if there is any inherited mutations, known as HIV genotypic resistance.

So, in the context of evolving and diversifying HIV organisms, epidemiology must get to the levels of the molecular and genetic to be able to continue to shine light upon the risk factors and analysis of transmission and disease dynamics.

Modelling risk

Planning by projecting into the future is a more recent development in epidemiology requiring particular skills akin to those of ‘risk management’. It’s like asking what health services will be needed in 20 years to manage HIV infection by reducing new HIV infections by 20%. It requires epidemiologists to model future scenarios based upon anticipating a set of risks which are likely to influence the outcome.

Epidemiology at the ASHMAustralasian Society for HIV Medicine. The peak Australasian organisation representing the medical and health sector in HIV/AIDS and related areas. Conference: lifting the bar

At the 20th ASHM conference in Perth, there were a number of important sessions that gave us more insights into the shifts and changes that have occurred in the Australian HIV epidemic.

I gained a real sense that ‘the bar had been lifted’ on what’s being achieved and on what’s possible to meet future challenges and add robust improvement to a range of current understandings. These include enhancements to HIV surveillance mechanisms and tools for detection of early HIV infection transmission links; improvements to surveillance reporting in the context of who gets AIDS in the era of HAARTHighly Active AntiRetroviral Therapy ??? aggressive treatment of HIV infection using several different drugs together.; and finally, to planning future health services program delivery through economic modelling, quality review and data linkage between labs and state health departments to inform new models of access and service delivery more appropriate to the current and future dynamics and spread of the HIV epidemic in Australia today.

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