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11 December 2019 | Story Leonie Bolleurs
Aids read more

According to Global Statistics, there were approximately 37,9 million people across the globe with HIV/Aids in 2018. They also state that in 2018, an estimated 1,7 million individuals worldwide became newly infected with HIV. 

In the city of Masvingo, Zimbabwe, Claris Shoko is a Statistics lecturer at the Great Zimbabwe University. In her PhD thesis at the University of the Free State (UFS) in the Department of Mathematical Statistics and Actuarial Sciences, she presented the argument that the inclusion of both the CD4 cell count and the viral-load counts in the monitoring and management of HIV+ patients on antiretroviral therapy (ART), is helping in reducing mortality rates, leading to improved life expectancy for HIV/Aids patients. 

She received her doctoral degree at the December UFS Graduation Ceremonies, with her thesis: Continuous-time Markov modelling of the effects of treatment regimens on HIV/Aids immunology and virology. 

CD4 cell count and viral-load count

Dr Shoko explains: “When the human immunodeficiency virus (HIV) enters the human body, the virus attacks the CD4 cells in their blood. This process damages CD4 cells, causing the number of white blood cells in the body to drop, making it difficult to fight infections.”

“Clinical markers such as CD4 cell count and viral-load count (number of HIV particles in a ml of blood) provide information about the progression of HIV/Aids in infected individuals. These markers fully define the immunology and the virology of HIV-infected individuals, thereby giving us a clear picture of how HIV/Aids evolve within an individual.”

Dr Shoko continues: “The development of highly active antiretroviral therapy (HAART) has helped substantially to reduce the death rate from HIV. HAART reduces viral load-count levels, blocking replication of HIV particles in the blood, resulting in an increase of CD4 cell counts and the life expectancy of individuals infected with HIV. This has made CD4 cell counts and viral-load counts the fundamental laboratory markers that are regularly used for patient management, in addition to predicting HIV/Aids disease progression or treatment outcomes.”

In the treatment of HIV/Aids, medical practitioners prescribe combination therapy to attack the virus at different stages of its life cycle, and medication to treat the opportunistic infections that may occur. “The introduction of combined antiretroviral therapy (cART) has led to the dramatic reduction in morbidity and mortality at both individual level and population level,” states Dr Shoko.

Once HIV-positive patients are put on cART, the effectiveness of treatment is monitored after the first three months and a further follow-up is done every six months thereafter. During the monitoring stages, CD4 cell count and viral load is measured. Patients are also screened for any tuberculosis (TB) co-infection and checked for any signs of drug resistance. These variables determine whether or not there is a need for treatment change. 

She continues: “Previous studies on HIV modelling could not include both CD4 cell count and viral load in one model, because of the collinearity between the two variables. In this study, the principal component approach for the treatment of collinearity between variables is used. Both variables were then included in one model, resulting in a better prediction of mortality than when only one of the variables is used.”

“Viral-load monitoring helps in checking for any possibilities of virologic failure or viral rebound, which increases the rate of mortality if not managed properly. CD4 cell count then comes in to monitor the potential development of opportunistic infections such as TB. TB is extremely fatal, but once detected and treated, the survival of HIV/Aids patients is assured,” Dr Shoko explains.

Markov model

She applied the Markov model in her study. The model, named after the Russian mathematician Andrey Markov, represents a general category of stochastic processes, characterised by six basic attributes: states, stages, actions, rewards, transitions, and constraints. 

According to Dr Shoko, Markov models assume that a patient is always in one of a finite number of discrete states, called Markov states. All events are modelled as transitions from one state to another. Each state is assigned a utility, and the contribution of this utility to the overall prognosis depends on the length of time spent in each state. For example, for a patient who is HIV positive, these states could be HIV+ (CD4 cell count above 200 cells/mm3), Aids (CD4 cell count below 200 cells/mm3) and Dead.

“Markov models are ideal for use in HIV/Aids studies, because they estimate the rate of transition between multiple-disease states while allowing for the possible reversibility of some states,” says Dr Shoko, quoting Hubbard and Zhou.

“Relatively fewer HIV modelling studies include a detailed description of the dynamics of HIV viral load count during stages of HIV disease progression. This could be due to the unavailability of data on viral load, particularly from low- and middle-income countries that have historically relied on monitoring CD4 cell counts for patients on ART because of higher costs of viral load-count testing,” Dr Shoko concludes

News Archive

Letter to students from Prof Jonathan Jansen about student protest action at the UFS
2015-10-21

Dear Students

Student protest action at the University of the Free State

I wish to make clear that the senior leadership of the University of the Free State understands and supports the demands from students and their leaders that higher education be accessible to all students, especially the poor. For the past six years we have done everything in our power to meet that commitment to students who are academically talented, but simply cannot afford to pay; that is why our tuition fees remain among the lowest in the country. Our efforts to raise private funding have enabled thousands more students to study at the UFS than would have been possible on the government subsidy only. Whether it is the Staff Fund contributions (yes, our staff empty their pockets to support student fees) or the No Student Hungry (NSH) bursary programme (yes, we raise funds for food bursaries), we will continue our drive to fund students who cannot afford higher education. Let me repeat, no student with a solid academic record will be denied access to studies simply because they cannot pay.

Now, to the matter at hand. There is a national demand from students for a 0% fee increment for 2016. The Minister’s response, after consultation with stakeholders, was that universities should cap their 2016 fee increases at 6%. Despite this initiative from government, the protests continue on virtually all campuses across South Africa for the ‘no fee’ increase.

Our response, as the UFS leadership, is to continue engaging the SRC as the chosen leadership of our students in trying to negotiate a settlement on the matter. We have worked around the clock to be available to student leaders to find some resolution on 2016 fees. While we understand the demands of students, as university leaders, we can only work with the government subsidy we receive. Any agreement reached, cannot and must not place the university at academic and financial risk in its ability to deliver public higher education to the country - if that happens, everybody loses. Still, no matter what happens in terms of the response from government, the leadership door at the UFS remains open to finding a mutually acceptable solution to all parties in these deliberations.

Students, we are deeply concerned by the violence, intimidation and threats from the small group of protesting students. These dangerous and demeaning behaviours, like disrupting classes and verbally abusing students and staff, undermine the legitimate quest of students for relief concerning tuition fees. Such behaviour is completely unacceptable and the university will take action where required. We must also remember that we have an obligation to all 30 000 students whose right to learn without fear of violence and intimidation must be respected.

In conclusion, over the past few years we have worked hard to build a culture of mutual respect and embrace as we worked through some very difficult challenges on campus. You would have noticed that the university leadership responded quickly and sympathetically to reason and respect in difficult situations of rage and demonstration. A minority of students, with some outsiders, have come onto the campus to break down that culture in which, while we might disagree, we continue to work on the basis of mutual respect. I urge all students that, as we engage of this important problem of enabling greater access to higher education, we continue to remain true to the core values of our Human Project.

Best Regards

Prof Jonathan Jansen
Vice-Chancellor and Rector
University of the Free State


Letter to students from Prof Jonathan Jansen about student protest actions at the UFS (Pdf format)

 

 

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