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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

The Great Pool of Exhilaration
2015-02-11

Photo: Albert van Biljon 

 

Boys’ roars and ladies’ shouts could be heard from miles away. From this, one could tell that the 2015 first-year’s Swimming Gala was bound to be an exciting one.

While RC Sports members were stressing, the first-years blissfully continued in song and excitement.

One would think that, after a hectic first week of classes, first-years would not have much energy left, but the atmosphere proved that Residence Committees (RCs) had prepared the individuals with rather motivating pep talks before the event. Most male residences put their best foot forward, not holding back on themed attire and additional instruments, while female residences sang and danced to the music provided. Not only were the masses competing to claim that they had the greatest spirit on this night, but they were also waiting to hear the results of the Spirit Cup for the first-years’ Athletics, which was cut short due to heavy rain showers. This simply added to the already intense anticipation of first-years and RC Sports members, as they would receive the results only at the end of the event.

The competition was tough as many of the first-years who competed moved with ease in the water as though it was second nature to them. This year’s gala saw quite a few talented, national swimmers competing, which left those who swam for pride and points intimidated. The excitement of the crowd was heightened as the relay section of the programme approached. This meant that the winners were to be announced soon.

In the ladies’ section, the residences were placed:
• 1st – Marjolein
• 2nd – Wag-‘n-Bietjie
• 3rd – Sonnedou

In the men’s section, the residences were placed:
• 1st – Armentum
• 2nd – Vishuis
• 3rd – Karee

When the time arrived for the announcement of the Spirit Cup winners, many were hopefully clenching their hearts for their name to be roared out. In most people’s opinion, it came as no surprise when Armentum walked away with the Spirit Cup for both the first-years’ Athletics and the Swimming Gala. Furthermore, Armentum’s broader South College community – of which Emily Hobhouse, Marjolein, NJ vd Merwe and Villa Bravado are also part – walked away with the cash prize for the best mascot.

By end of the night, everyone, no matter if they were drenched or dry, experienced the exciting sporting atmosphere at Kovsies that they’ve now become a part of.

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