Wendy Stevens - Academia.edu (original) (raw)

Papers by Wendy Stevens

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2012

The high demand for SARS-CoV-2 tests but limited supply to South African laboratories early in th... more The high demand for SARS-CoV-2 tests but limited supply to South African laboratories early in the COVID19 pandemic, resulted in a heterogenous diagnostic footprint of open and closed molecular testing platforms. Novel approaches were required to monitor test quality especially during the introduction of newly circulating variants. The National Health Laboratory Service centrally collected cycle threshold (Ct) values from 1,497,669 test results reported from six commonly used PCR assays in 36 months, and visually monitored changes in their median Ct within a 28-day centered moving average for each assays’ gene targets. This continuous quality monitoring rapidly identified delayed hybridization of RdRp in the Allplex™ SARS-CoV-2 assay due to the Delta (B.1.617.2) variant; S-gene target failure in the TaqPath™ COVID-19 assay due to B.1.1.7 (Alpha) and the B.1.1.529 (Omicron); and recently E-gene delayed hybridization in the Xpert® Xpress SARS-CoV-2 due to XBB.1.5. This near “real-time...

Antiviral Therapy

Access to highly active antiretroviral therapy (HAART) for persons infected with HIV in sub-Sahar... more Access to highly active antiretroviral therapy (HAART) for persons infected with HIV in sub-Saharan Africa has greatly improved over the past few years. However, data on long-term clinical outcomes of Africans receiving HAART, patterns of HIV resistance to antiretroviral drugs and implications of HIV type-1 (HIV-1) subtype diversity in Africa for resistance, are limited. In resource-limited settings, concerns have been raised that deficiencies in health systems could create the conditions for accelerated development of resistance. Coordinated surveillance systems are being established to assess the emergence of resistance and the factors associated with resistance development, and to create the possibility for adjusting treatment guidelines as necessary. The purpose of this report is to review the literature on HIV-1 resistance to antiretroviral drugs in sub-Saharan Africa, in relation to the drug regimens used in Africa, HIV-1 subtype diversity and overall prevalence of resistance....

This article cites 17 articles, 4 of which can be accessed free at:

MMWR. Morbidity and Mortality Weekly Report, 2021

Scientific Reports, 2018

In ART programs in sub-Saharan Africa, a growing proportion of HIV-infected persons initiating fi... more In ART programs in sub-Saharan Africa, a growing proportion of HIV-infected persons initiating first-line antiretroviral therapy (ART) have a history of prior antiretroviral drug use (PAU). We assessed the effect of PAU on the risk of pre-treatment drug resistance (PDR) and virological failure (VF) in a multicountry cohort of HIV-infected adults initiated on a standard non-nucleoside reverse transcriptase inhibitor (NNRTI)-based first-line ART. Multivariate logistic regression was used to assess the associations between PAU, PDR and VF (defined as viral load ≥400 cps/mL). Causal mediation analysis was used to assess the proportion of the effect of PAU on VF that could be eliminated by intervening on PDR. Of 2737 participants, 122 (4.5%) had a history of PAU. Participants with PAU had a 7.2-fold (95% CI 4.4–11.7) risk of carrying PDR and a 3.1-fold (95% CI 1.6–6.1) increased risk of VF, compared to antiretroviral-naïve participants. Controlling for PDR would eliminate nearly half the...

PLoS medicine, 2018

Systematic reviews have described high rates of attrition in patients with HIV receiving antiretr... more Systematic reviews have described high rates of attrition in patients with HIV receiving antiretroviral therapy (ART). However, migration and clinical transfer may lead to an overestimation of attrition (death and loss to follow-up). Using a newly linked national laboratory database in South Africa, we assessed national retention in South Africa's national HIV program. Patients receiving care in South Africa's national HIV program are monitored through regular CD4 count and viral load testing. South Africa's National Health Laboratory Service has maintained a database of all public-sector CD4 count and viral load results since 2004. We linked individual laboratory results to patients using probabilistic matching techniques, creating a national HIV cohort. Validation of our approach in comparison to a manually matched dataset showed 9.0% undermatching and 9.5% overmatching. We analyzed data on patients initiating ART in the public sector from April 1, 2004, to December 31...

BMC health services research, Jan 17, 2017

Poor clinical record keeping hinders health systems monitoring and patient care in many low resou... more Poor clinical record keeping hinders health systems monitoring and patient care in many low resource settings. We develop and validate a novel method to impute dates of antiretroviral treatment (ART) initiation from routine laboratory data in South Africa's public sector HIV program. This method will enable monitoring of the national ART program using real-time laboratory data, avoiding the error potential of chart review. We developed an algorithm to impute ART start dates based on the date of a patient's "ART workup", i.e. the laboratory tests used to determine treatment readiness in national guidelines, and the time from ART workup to initiation based on clinical protocols (21 days). To validate the algorithm, we analyzed data from two large clinical HIV cohorts: Hlabisa HIV Treatment and Care Programme in rural KwaZulu-Natal; and Right to Care Cohort in urban Gauteng. Both cohorts contain known ART initiation dates and laboratory results imported directly from ...

International Journal of Infectious Diseases, 2014

MMWR. Morbidity and mortality weekly report, Jan 27, 2015

To achieve global targets for universal treatment set forth by the Joint United Nations Programme... more To achieve global targets for universal treatment set forth by the Joint United Nations Programme on human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) (UNAIDS), viral load monitoring for HIV-infected persons receiving antiretroviral therapy (ART) must become the standard of care in low- and middle-income countries (LMIC) (1). CDC and other U.S. government agencies, as part of the President's Emergency Plan for AIDS Relief, are supporting multiple countries in sub-Saharan Africa to change from the use of CD4 cell counts for monitoring of clinical response to ART to the use of viral load monitoring, which is the standard of care in developed countries. Viral load monitoring is the preferred method for immunologic monitoring because it enables earlier and more accurate detection of treatment failure before immunologic decline. This report highlights the initial successes and challenges of viral load monitoring in seven countries that have chosen to scale ...

Journal of the International AIDS Society, 2015

IntroductionThe effectiveness of antiretroviral therapy (ART) is assessed by measuring CD4 cell c... more IntroductionThe effectiveness of antiretroviral therapy (ART) is assessed by measuring CD4 cell counts and viral load. Recent studies have questioned the added value of routine CD4 cell count measures in patients who are virologically suppressed.MethodsWe systematically searched three databases and two conference sites up to 31 October 2014 for studies reporting CD4 changes among patients who were on ART and virologically suppressed. No geographic, language or age restrictions were applied.Results and discussionWe identified 12 published and 1 unpublished study reporting CD4 changes among 20,297 virologically suppressed patients. The pooled proportion of patients who experienced an unexplained, confirmed CD4 decline was 0.4% (95% CI 0.2–0.6%). Results were not influenced by duration of follow‐up, age, study design or region of economic development. No studies described clinical adverse events among virologically suppressed patients who experienced CD4 declines.ConclusionsThe finding...

South African Medical Journal, 2014

Journal of the International AIDS Society, 2012

BackgroundPoint‐of‐care CD4 testing can provide immediate CD4 reporting at HIV‐testing sites. Thi... more BackgroundPoint‐of‐care CD4 testing can provide immediate CD4 reporting at HIV‐testing sites. This study evaluated performance of capillary blood sampling using the point‐of‐care Pima™ CD4 device in representative primary health care clinics doing HIV testing.MethodsPrior to testing, prescribed capillary‐sampling and instrument training was undertaken by suppliers across all sites. Matching venous EDTA samples were drawn throughout for comparison to laboratory predicate methodology (PLG/CD4). In Phase I, Pima™ cartridges were pipette‐filled with EDTA venous blood in the laboratory (N = 100). In Phase II (N = 77), Pima™ CD4 with capillary sampling was performed by a single operator in a hospital‐based antenatal clinic. During subsequent field testing, Pima™ CD4 with capillary sampling was performed in primary health care clinics on HIV‐positive patients by multiple attending nursing personnel in a rural clinic (Phase‐IIIA, N = 96) and an inner‐city clinic (Phase‐IIIB, N = 139).Result...

Journal of Clinical Microbiology, 2005

Although human immunodeficiency virus type 1 (HIV-1) RNA is the acknowledged “gold standard” mark... more Although human immunodeficiency virus type 1 (HIV-1) RNA is the acknowledged “gold standard” marker for monitoring disease activity in patients receiving highly active antiretroviral therapy (HAART), it remains unaffordable in resource-constrained settings. The present study investigated two commercially available kits for the detection of HIV-1 viral load markers as more affordable alternatives to HIV-1 RNA quantitation. The greatly improved heat-denatured, signal-boosted HiSens HIV-1 p24 Ag Ultra kit (Perkin-Elmer) and the ExaVir Load Quantitative HIV-RT kit (Cavidi Tech AB) were compared with the Amplicor HIV-1 Monitor (version 1.5) assay (Roche Molecular Systems Inc.). A total of 117 samples containing HIV-1 subtype C were analyzed by all three methodologies. Eighty-nine of these samples represented serial measurements from 20 patients receiving HAART. The remaining samples analyzed were from a group of treatment-naïve patients. The association between the p24 antigen assay and...

Journal of Clinical Microbiology, 2013

The use of dried culture spots (DCSs) has been reported in the verification of GeneXpert instrume... more The use of dried culture spots (DCSs) has been reported in the verification of GeneXpert instruments as being “fit for purpose” for the South African National implementation program. We investigated and compared the performance of the DCSs for verification across different bulk batches, testing the settings and cadre of staff, and the Xpert MTB/RIF assay version. Four bulk batches (V005 to V008) were used to prepare (i) 619 DCS panels for laboratory testing on G3 or G4 cartridges by a technologist, (ii) 13 DCS panels (batch V005) used for clinic verification on G3 cartridges by a nurse or lay counselor, and (iii) 20 DCS panels (batch V005) used for the verification of 10 GeneXpert 16 module instruments in mobile vehicles on the G3 cartridge performed by a scientist. The stabilities of the DCSs over 6 months at 4°C, room temperature, and 37°C were investigated. The mean cycle threshold ( C T ) and standard deviation (SD) for probe A were calculated. The proportions of variability in ...

Journal of Clinical Microbiology, 2012

The Roche LightCycler mycobacterium detection molecular assay for Mycobacterium tuberculosis , M.... more The Roche LightCycler mycobacterium detection molecular assay for Mycobacterium tuberculosis , M. avium , and M. kansasii , was applied to tissue specimens. It performed well on lymph node and cerebrospinal fluid specimens and less well on lung, liver, and bone marrow core biopsy specimens, but used in conjunction with a clinical suspicion of tuberculosis, it could augment patient management.

JAIDS Journal of Acquired Immune Deficiency Syndromes, 2011

Background: HIV infection has been associated with an increased risk of non-Hodgkin lymphoma, par... more Background: HIV infection has been associated with an increased risk of non-Hodgkin lymphoma, particularly in the first world. Despite the high burden of HIV infection in sub-Saharan regions, published data on HIV and malignancies are sparse from these areas. Materials and Methods: We recently published data on lymphomas diagnosed from January 2004 to December 2006, at a single center in Johannesburg, to serve as a baseline for long-term comparison during the period of highly active antiretroviral therapy rollout. We report a retrospective analysis of the follow-up data collected from January 2007 to December 2009 at the Johannesburg academic hospital complex (Gauteng, South Africa). Results: There were 2225 new diagnoses of lymphoproliferative disorders made during 2007-2009 as compared with 1897 cases diagnosed during 2004-2006. A significant increase in both highgrade B-cell lymphomas and Hodgkin lymphoma was documented during 2007-2009. This was associated with a statistically significant increase in HIV prevalence in those tested (from 44.3% in 2004-2006 to 62.0% in 2007-2009). HIV-positive patients presented at a statistically significantly younger median age and showed a relative overrepresentation of females when compared with HIV-negative patients. HIV-positive patients were diagnosed at later stages of HIV infection when compared with patients in the first world. Conclusions: The pattern of lymphoma subtypes and the demographics of the patients diagnosed have altered in association with significantly increased HIV prevalence. These changes have important public health implications. In particular, scale-up and earlier access to highly active antiretroviral therapy is essential with continued monitoring as access to therapy improves.

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2012

The high demand for SARS-CoV-2 tests but limited supply to South African laboratories early in th... more The high demand for SARS-CoV-2 tests but limited supply to South African laboratories early in the COVID19 pandemic, resulted in a heterogenous diagnostic footprint of open and closed molecular testing platforms. Novel approaches were required to monitor test quality especially during the introduction of newly circulating variants. The National Health Laboratory Service centrally collected cycle threshold (Ct) values from 1,497,669 test results reported from six commonly used PCR assays in 36 months, and visually monitored changes in their median Ct within a 28-day centered moving average for each assays’ gene targets. This continuous quality monitoring rapidly identified delayed hybridization of RdRp in the Allplex™ SARS-CoV-2 assay due to the Delta (B.1.617.2) variant; S-gene target failure in the TaqPath™ COVID-19 assay due to B.1.1.7 (Alpha) and the B.1.1.529 (Omicron); and recently E-gene delayed hybridization in the Xpert® Xpress SARS-CoV-2 due to XBB.1.5. This near “real-time...

Antiviral Therapy

Access to highly active antiretroviral therapy (HAART) for persons infected with HIV in sub-Sahar... more Access to highly active antiretroviral therapy (HAART) for persons infected with HIV in sub-Saharan Africa has greatly improved over the past few years. However, data on long-term clinical outcomes of Africans receiving HAART, patterns of HIV resistance to antiretroviral drugs and implications of HIV type-1 (HIV-1) subtype diversity in Africa for resistance, are limited. In resource-limited settings, concerns have been raised that deficiencies in health systems could create the conditions for accelerated development of resistance. Coordinated surveillance systems are being established to assess the emergence of resistance and the factors associated with resistance development, and to create the possibility for adjusting treatment guidelines as necessary. The purpose of this report is to review the literature on HIV-1 resistance to antiretroviral drugs in sub-Saharan Africa, in relation to the drug regimens used in Africa, HIV-1 subtype diversity and overall prevalence of resistance....

This article cites 17 articles, 4 of which can be accessed free at:

MMWR. Morbidity and Mortality Weekly Report, 2021

Scientific Reports, 2018

In ART programs in sub-Saharan Africa, a growing proportion of HIV-infected persons initiating fi... more In ART programs in sub-Saharan Africa, a growing proportion of HIV-infected persons initiating first-line antiretroviral therapy (ART) have a history of prior antiretroviral drug use (PAU). We assessed the effect of PAU on the risk of pre-treatment drug resistance (PDR) and virological failure (VF) in a multicountry cohort of HIV-infected adults initiated on a standard non-nucleoside reverse transcriptase inhibitor (NNRTI)-based first-line ART. Multivariate logistic regression was used to assess the associations between PAU, PDR and VF (defined as viral load ≥400 cps/mL). Causal mediation analysis was used to assess the proportion of the effect of PAU on VF that could be eliminated by intervening on PDR. Of 2737 participants, 122 (4.5%) had a history of PAU. Participants with PAU had a 7.2-fold (95% CI 4.4–11.7) risk of carrying PDR and a 3.1-fold (95% CI 1.6–6.1) increased risk of VF, compared to antiretroviral-naïve participants. Controlling for PDR would eliminate nearly half the...

PLoS medicine, 2018

Systematic reviews have described high rates of attrition in patients with HIV receiving antiretr... more Systematic reviews have described high rates of attrition in patients with HIV receiving antiretroviral therapy (ART). However, migration and clinical transfer may lead to an overestimation of attrition (death and loss to follow-up). Using a newly linked national laboratory database in South Africa, we assessed national retention in South Africa's national HIV program. Patients receiving care in South Africa's national HIV program are monitored through regular CD4 count and viral load testing. South Africa's National Health Laboratory Service has maintained a database of all public-sector CD4 count and viral load results since 2004. We linked individual laboratory results to patients using probabilistic matching techniques, creating a national HIV cohort. Validation of our approach in comparison to a manually matched dataset showed 9.0% undermatching and 9.5% overmatching. We analyzed data on patients initiating ART in the public sector from April 1, 2004, to December 31...

BMC health services research, Jan 17, 2017

Poor clinical record keeping hinders health systems monitoring and patient care in many low resou... more Poor clinical record keeping hinders health systems monitoring and patient care in many low resource settings. We develop and validate a novel method to impute dates of antiretroviral treatment (ART) initiation from routine laboratory data in South Africa's public sector HIV program. This method will enable monitoring of the national ART program using real-time laboratory data, avoiding the error potential of chart review. We developed an algorithm to impute ART start dates based on the date of a patient's "ART workup", i.e. the laboratory tests used to determine treatment readiness in national guidelines, and the time from ART workup to initiation based on clinical protocols (21 days). To validate the algorithm, we analyzed data from two large clinical HIV cohorts: Hlabisa HIV Treatment and Care Programme in rural KwaZulu-Natal; and Right to Care Cohort in urban Gauteng. Both cohorts contain known ART initiation dates and laboratory results imported directly from ...

International Journal of Infectious Diseases, 2014

MMWR. Morbidity and mortality weekly report, Jan 27, 2015

To achieve global targets for universal treatment set forth by the Joint United Nations Programme... more To achieve global targets for universal treatment set forth by the Joint United Nations Programme on human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) (UNAIDS), viral load monitoring for HIV-infected persons receiving antiretroviral therapy (ART) must become the standard of care in low- and middle-income countries (LMIC) (1). CDC and other U.S. government agencies, as part of the President's Emergency Plan for AIDS Relief, are supporting multiple countries in sub-Saharan Africa to change from the use of CD4 cell counts for monitoring of clinical response to ART to the use of viral load monitoring, which is the standard of care in developed countries. Viral load monitoring is the preferred method for immunologic monitoring because it enables earlier and more accurate detection of treatment failure before immunologic decline. This report highlights the initial successes and challenges of viral load monitoring in seven countries that have chosen to scale ...

Journal of the International AIDS Society, 2015

IntroductionThe effectiveness of antiretroviral therapy (ART) is assessed by measuring CD4 cell c... more IntroductionThe effectiveness of antiretroviral therapy (ART) is assessed by measuring CD4 cell counts and viral load. Recent studies have questioned the added value of routine CD4 cell count measures in patients who are virologically suppressed.MethodsWe systematically searched three databases and two conference sites up to 31 October 2014 for studies reporting CD4 changes among patients who were on ART and virologically suppressed. No geographic, language or age restrictions were applied.Results and discussionWe identified 12 published and 1 unpublished study reporting CD4 changes among 20,297 virologically suppressed patients. The pooled proportion of patients who experienced an unexplained, confirmed CD4 decline was 0.4% (95% CI 0.2–0.6%). Results were not influenced by duration of follow‐up, age, study design or region of economic development. No studies described clinical adverse events among virologically suppressed patients who experienced CD4 declines.ConclusionsThe finding...

South African Medical Journal, 2014

Journal of the International AIDS Society, 2012

BackgroundPoint‐of‐care CD4 testing can provide immediate CD4 reporting at HIV‐testing sites. Thi... more BackgroundPoint‐of‐care CD4 testing can provide immediate CD4 reporting at HIV‐testing sites. This study evaluated performance of capillary blood sampling using the point‐of‐care Pima™ CD4 device in representative primary health care clinics doing HIV testing.MethodsPrior to testing, prescribed capillary‐sampling and instrument training was undertaken by suppliers across all sites. Matching venous EDTA samples were drawn throughout for comparison to laboratory predicate methodology (PLG/CD4). In Phase I, Pima™ cartridges were pipette‐filled with EDTA venous blood in the laboratory (N = 100). In Phase II (N = 77), Pima™ CD4 with capillary sampling was performed by a single operator in a hospital‐based antenatal clinic. During subsequent field testing, Pima™ CD4 with capillary sampling was performed in primary health care clinics on HIV‐positive patients by multiple attending nursing personnel in a rural clinic (Phase‐IIIA, N = 96) and an inner‐city clinic (Phase‐IIIB, N = 139).Result...

Journal of Clinical Microbiology, 2005

Although human immunodeficiency virus type 1 (HIV-1) RNA is the acknowledged “gold standard” mark... more Although human immunodeficiency virus type 1 (HIV-1) RNA is the acknowledged “gold standard” marker for monitoring disease activity in patients receiving highly active antiretroviral therapy (HAART), it remains unaffordable in resource-constrained settings. The present study investigated two commercially available kits for the detection of HIV-1 viral load markers as more affordable alternatives to HIV-1 RNA quantitation. The greatly improved heat-denatured, signal-boosted HiSens HIV-1 p24 Ag Ultra kit (Perkin-Elmer) and the ExaVir Load Quantitative HIV-RT kit (Cavidi Tech AB) were compared with the Amplicor HIV-1 Monitor (version 1.5) assay (Roche Molecular Systems Inc.). A total of 117 samples containing HIV-1 subtype C were analyzed by all three methodologies. Eighty-nine of these samples represented serial measurements from 20 patients receiving HAART. The remaining samples analyzed were from a group of treatment-naïve patients. The association between the p24 antigen assay and...

Journal of Clinical Microbiology, 2013

The use of dried culture spots (DCSs) has been reported in the verification of GeneXpert instrume... more The use of dried culture spots (DCSs) has been reported in the verification of GeneXpert instruments as being “fit for purpose” for the South African National implementation program. We investigated and compared the performance of the DCSs for verification across different bulk batches, testing the settings and cadre of staff, and the Xpert MTB/RIF assay version. Four bulk batches (V005 to V008) were used to prepare (i) 619 DCS panels for laboratory testing on G3 or G4 cartridges by a technologist, (ii) 13 DCS panels (batch V005) used for clinic verification on G3 cartridges by a nurse or lay counselor, and (iii) 20 DCS panels (batch V005) used for the verification of 10 GeneXpert 16 module instruments in mobile vehicles on the G3 cartridge performed by a scientist. The stabilities of the DCSs over 6 months at 4°C, room temperature, and 37°C were investigated. The mean cycle threshold ( C T ) and standard deviation (SD) for probe A were calculated. The proportions of variability in ...

Journal of Clinical Microbiology, 2012

The Roche LightCycler mycobacterium detection molecular assay for Mycobacterium tuberculosis , M.... more The Roche LightCycler mycobacterium detection molecular assay for Mycobacterium tuberculosis , M. avium , and M. kansasii , was applied to tissue specimens. It performed well on lymph node and cerebrospinal fluid specimens and less well on lung, liver, and bone marrow core biopsy specimens, but used in conjunction with a clinical suspicion of tuberculosis, it could augment patient management.

JAIDS Journal of Acquired Immune Deficiency Syndromes, 2011

Background: HIV infection has been associated with an increased risk of non-Hodgkin lymphoma, par... more Background: HIV infection has been associated with an increased risk of non-Hodgkin lymphoma, particularly in the first world. Despite the high burden of HIV infection in sub-Saharan regions, published data on HIV and malignancies are sparse from these areas. Materials and Methods: We recently published data on lymphomas diagnosed from January 2004 to December 2006, at a single center in Johannesburg, to serve as a baseline for long-term comparison during the period of highly active antiretroviral therapy rollout. We report a retrospective analysis of the follow-up data collected from January 2007 to December 2009 at the Johannesburg academic hospital complex (Gauteng, South Africa). Results: There were 2225 new diagnoses of lymphoproliferative disorders made during 2007-2009 as compared with 1897 cases diagnosed during 2004-2006. A significant increase in both highgrade B-cell lymphomas and Hodgkin lymphoma was documented during 2007-2009. This was associated with a statistically significant increase in HIV prevalence in those tested (from 44.3% in 2004-2006 to 62.0% in 2007-2009). HIV-positive patients presented at a statistically significantly younger median age and showed a relative overrepresentation of females when compared with HIV-negative patients. HIV-positive patients were diagnosed at later stages of HIV infection when compared with patients in the first world. Conclusions: The pattern of lymphoma subtypes and the demographics of the patients diagnosed have altered in association with significantly increased HIV prevalence. These changes have important public health implications. In particular, scale-up and earlier access to highly active antiretroviral therapy is essential with continued monitoring as access to therapy improves.

Cloud computing is emerging as a new paradigm in health care information technology strategies an... more Cloud computing is emerging as a new paradigm in health care information technology strategies and the growth of the industry. Despite reports emerging as early as the 1950s hinting at the potential of this approach, the strength of this is only now being realized in the health care sector. This is a simple principle of service-orientated architecture delivering a service around data rather than a product. The main enabling technology for cloud computing is virtualization. Virtualization is the ability to allow the system to operate independently of the hardware from the cloud via the Internet, so one can provide information to other users of hardware or software. In addition, resources can be shared within and between organizations to improve economies of scale. Data can be transferred in a computer network that is able to compartmentalize your needs.