Modeling State Firearm Law Adoption Using Temporal Network Models.

Policy Points Promoting healthy public policies is a national priority, but state policy adoption is driven by a complex set of internal and external factors. This study employs new social network methods to identify underlying connections among states and to predict the likelihood of new firearm-related policy adoption given changes to this interstate network. This approach could be used to assess the likelihood that a given state will adopt a specific new firearm-related law and to identify points of influence that could either inhibit or promote wider diffusion of specific laws. CONTEXT: US states are largely responsible for the regulation of firearms within their borders. Each state has developed a different legal environment with regard to firearms based on different values and beliefs of citizens, legislators, governors, and other stakeholders. Predicting the types of firearm laws that states may adopt is therefore challenging. METHODS: We propose a parsimonious model for this complex process and provide credible predictions of state firearm laws by estimating the likelihood they will be passed in the future. We employ a temporal exponential-family random graph model to capture the bipartite state law-state network data over time, allowing for complex interdependencies and their temporal evolution. Using data on all state firearm laws over the period 1979-2020, we estimate these models' parameters while controlling for factors associated with firearm law adoption, including internal and external state characteristics. Predictions of future firearm law passage are then calculated based on a number of scenarios to assess the effects of a given type of firearm law being passed in the future by a given state. FINDINGS: Results show that a set of internal state factors are important predictors of firearm law adoption, but the actions of neighboring states may be just as important. Analysis of scenarios provide insights into the mechanics of how adoption of laws by specific states (or groups of states) may perturb the rest of the network structure and alter the likelihood that new laws would become more (or less) likely to continue to diffuse to other states. CONCLUSIONS: The methods used here outperform standard approaches for policy diffusion studies and afford predictions that are superior to those of an ensemble of machine learning tools. The proposed framework could have applications for the study of policy diffusion in other domains.

The Diffusion of Punitive Firearm Preemption Laws Across U.S. States.

INTRODUCTION: Firearm violence is a public health crisis. Most states prohibit local firearm laws, but some states have laws that allow for lawsuits and other penalties against local governments and lawmakers who pass firearm laws deemed preempted. These punitive firearm preemptive laws may reduce firearm policy innovation, discussion, and adoption beyond preemption alone. Yet, it is unknown how these laws spread from state to state. METHODS: In 2022, using an event history analysis framework with state dyads, logistic regression models estimate the factors associated with adoption and diffusion of firearm punitive preemption laws, including state-level demographic, economic, legal, political, population, and state-neighbor factors. RESULTS: As of 2021, 15 states had punitive firearm preemption laws. Higher numbers of background checks (AOR=1.50; 95% CI=1.15, 2.04), more conservative government ideology (AOR=7.79; 95% CI=2.05, 35.02), lower per capita income (AOR=0.16; 95% CI=0.05, 0.44), a higher number of permissive state firearm laws (AOR=2.75; 95% CI=1.57, 5.30), and neighboring state passage of the law (AOR=3.97; 95% CI=1.52, 11.51) were associated with law adoption. CONCLUSIONS: Both internal and external state factors predict the adoption of punitive firearm preemption. This study may provide insight into which states are susceptible to adoption in the future. Advocates, especially in neighboring states without such laws, may want to focus their firearm safety policy efforts on opposing the passage of punitive firearm preemption.

What factors drive state firearm law adoption? An application of exponential-family random graph models.

Guns are a ubiquitous feature of contemporary US culture, driven, at least partly, by firearms' constitutional enshrinement. However, the majority of laws intended to restrict or expand firearm access and use are formulated and passed in the states, leading to 50 different firearm-related legal environments. To date, little is known about why some states pass more restrictive or permissive firearm laws than others. In this article, we identify patterns of firearm law adoption across states, by framing the problem as a bipartite network (states connected to laws and laws connected to states) that is the result of a complex, and interconnected system of unobserved forces. We employ Exponential-family Random Graph Models (ERGMs), a class of statistical network models that allow for the dispensing of the assumptions of statistical independence, to identify factors that increase or decrease the likelihood of states adopting permissive or restrictive firearms laws over the period 1979 to 2020. Results show that more progressive state governments are associated with a higher chance of enacting restrictive firearm laws, and a lower chance of enacting permissive ones. Conservative state governments are associated with the analogous reversed association. States are more likely to adopt laws if bordering states have also adopted that law. For both restrictive and permissive laws the presence of a law in a neighboring state increased the conditional likelihood of a state having that law, that is laws diffuse across state borders. High levels of homicides are associated with a state having adopted more permissive, but not more restrictive, firearm laws. In summary, these results point to a complex interplay of state internal and external factors that seem to drive different patterns of firearm law adoption Based on these results, future work using related classes of models that take into account the time evolution of the network structure may provide a means to predict the likelihood of future law adoption.

Comparing the Real-World Performance of Exponential-family Random Graph Models and Latent Order Logistic Models for Social Network Analysis.

Exponential-family Random Graph models (ERGM) are widely used in social network analysis when modelling data on the relations between actors. ERGMs are typically interpreted as a snapshot of a network at a given point in time or in a final state. The recently proposed Latent Order Logistic model (LOLOG) directly allows for a latent network formation process. We assess the real-world performance of these models when applied to typical networks modelled by researchers. Specifically, we model data from an ensemble of articles in the journal Social Networks with published ERGM fits, and compare the ERGM fit to a comparable LOLOG fit. We demonstrate that the LOLOG models are, in general, in qualitative agreement with the ERGM models, and provide at least as good a model fit. In addition they are typically faster and easier to fit to data, without the tendency for degeneracy that plagues ERGMs. Our results support the general use of LOLOG models in circumstances where ERGMs are considered.

Islands of linkage in an ocean of pervasive recombination reveals two-speed evolution of human cytomegalovirus genomes.

Human cytomegalovirus (HCMV) infects most of the population worldwide, persisting throughout the host's life in a latent state with periodic episodes of reactivation. While typically asymptomatic, HCMV can cause fatal disease among congenitally infected infants and immunocompromised patients. These clinical issues are compounded by the emergence of antiviral resistance and the absence of an effective vaccine, the development of which is likely complicated by the numerous immune evasins encoded by HCMV to counter the host's adaptive immune responses, a feature that facilitates frequent super-infections. Understanding the evolutionary dynamics of HCMV is essential for the development of effective new drugs and vaccines. By comparing viral genomes from uncultivated or low-passaged clinical samples of diverse origins, we observe evidence of frequent homologous recombination events, both recent and ancient, and no structure of HCMV genetic diversity at the whole-genome scale. Analysis of individual gene-scale loci reveals a striking dichotomy: while most of the genome is highly conserved, recombines essentially freely and has evolved under purifying selection, 21 genes display extreme diversity, structured into distinct genotypes that do not recombine with each other. Most of these hyper-variable genes encode glycoproteins involved in cell entry or escape of host immunity. Evidence that half of them have diverged through episodes of intense positive selection suggests that rapid evolution of hyper-variable loci is likely driven by interactions with host immunity. It appears that this process is enabled by recombination unlinking hyper-variable loci from strongly constrained neighboring sites. It is conceivable that viral mechanisms facilitating super-infection have evolved to promote recombination between diverged genotypes, allowing the virus to continuously diversify at key loci to escape immune detection, while maintaining a genome optimally adapted to its asymptomatic infectious lifecycle.

Astrovirus VA1/HMO-C: an increasingly recognized neurotropic pathogen in immunocompromised patients.

BACKGROUND: An 18-month-old boy developed encephalopathy, for which extensive investigation failed to identify an etiology, 6 weeks after stem cell transplant. To exclude a potential infectious cause, we performed high-throughput RNA sequencing on brain biopsy. METHODS: RNA-Seq was performed on an Illumina Miseq, generating 20 million paired-end reads. Nonhost data were checked for similarity to known organisms using BLASTx. The full viral genome was sequenced by primer walking. RESULTS: We identified an astrovirus, HAstV-VA1/HMO-C-UK1(a), which was highly divergent from human astrovirus (HAstV 1-8) genotypes, but closely related to VA1/HMO-C astroviruses, including one recovered from a case of fatal encephalitis in an immunosuppressed child. The virus was detected in stool and serum, with highest levels in brain and cerebrospinal fluid (CSF). Immunohistochemistry of the brain biopsy showed positive neuronal staining. A survey of 680 stool and 349 CSF samples identified a related virus in the stool of another immunosuppressed child. CONCLUSIONS: The discovery of HAstV-VA1/HMO-C-UK1(a) as the cause of encephalitis in this case provides further evidence that VA1/HMO-C viruses, unlike HAstV 1-8, are neuropathic, particularly in immunocompromised patients, and should be considered in the differential diagnosis of encephalopathy. With a turnaround from sample receipt to result of <1 week, we confirm that RNA-Seq presents a valuable diagnostic tool in unexplained encephalitis.

Evaluation of non-extracted genital swabs for real-time HSV PCR.

Nucleic acid extraction of clinical samples is accepted as a key requirement in molecular diagnostics. At Barts Health NHS Trust, swabs taken from patients with clinical suspicion of HSV infection were routinely extracted on the Qiagen MDx BioRobot prior to testing with a real-time triplex PCR for HSV1, HSV2, and VZV. The aim of this study was to adapt an existing HSV1/HSV2/VZV real-time PCR by replacing VZV with phocine herpesvirus 1 (PhHV) as an internal control (IC) and evaluate whether this adapted assay required the nucleic acid extraction step for predominantly genital swabs. First 313 non-extracted and extracted swabs were tested in parallel with the existing triplex HSV1/HSV2/VZV real-time PCR. The second stage involved testing 176 non-extracted swabs using a triplex real-time PCR for HSV1, HSV2, and PhHV and comparing the results with the samples extracted and tested by the original triplex assay. The results correlated well when the existing assay was used, with only three non-extracted samples that would have been reported as negative compared to the extracted sample result (Cq s 33, 39, 35-two samples HSV1, one sample HSV2). In the evaluation using the adapted assay containing the IC, two of 176 samples were discordant, where a HSV negative non-extracted sample result would have been reported differently to the extracted sample result (Cq s 32, 33-both HSV1). This study demonstrated that it is feasible to test non-extracted swabs for HSV in a real-time PCR that includes an IC. J. Med. Virol. 87: 125-129, 2015. © 2014 Wiley Periodicals, Inc.

Human telomeres that carry an integrated copy of human herpesvirus 6 are often short and unstable, facilitating release of the viral genome from the chromosome.

Linear chromosomes are stabilized by telomeres, but the presence of short dysfunctional telomeres triggers cellular senescence in human somatic tissues, thus contributing to ageing. Approximately 1% of the population inherits a chromosomally integrated copy of human herpesvirus 6 (CI-HHV-6), but the consequences of integration for the virus and for the telomere with the insertion are unknown. Here we show that the telomere on the distal end of the integrated virus is frequently the shortest measured in somatic cells but not the germline. The telomere carrying the CI-HHV-6 is also prone to truncations that result in the formation of a short telomere at a novel location within the viral genome. We detected extra-chromosomal circular HHV-6 molecules, some surprisingly comprising the entire viral genome with a single fully reconstituted direct repeat region (DR) with both terminal cleavage and packaging elements (PAC1 and PAC2). Truncated CI-HHV-6 and extra-chromosomal circular molecules are likely reciprocal products that arise through excision of a telomere-loop (t-loop) formed within the CI-HHV-6 genome. In summary, we show that the CI-HHV-6 genome disrupts stability of the associated telomere and this facilitates the release of viral sequences as circular molecules, some of which have the potential to become fully functioning viruses.

Classification of HHV-6A and HHV-6B as distinct viruses.

Shortly after the discovery of human herpesvirus 6 (HHV-6), two distinct variants, HHV-6A and HHV-6B, were identified. In 2012, the International Committee on Taxonomy of Viruses (ICTV) classified HHV-6A and HHV-6B as separate viruses. This review outlines several of the documented epidemiological, biological, and immunological distinctions between HHV-6A and HHV-6B, which support the ICTV classification. The utilization of virus-specific clinical and laboratory assays for distinguishing HHV-6A and HHV-6B is now required for further classification. For clarity in biological and clinical distinctions between HHV-6A and HHV-6B, scientists and physicians are herein urged, where possible, to differentiate carefully between HHV-6A and HHV-6B in all future publications.

Genome Sequence of Human Herpesvirus 7 Strain UCL-1.

The sequence of human herpesvirus 7 (HHV-7) strain UCL-1 was determined using target enrichment and next-generation sequencing methods. We have identified 86 putative open reading frames (ORFs), and comparative sequence analyses demonstrate that this strain is closely related to the previously sequenced HHV-7 strains RK and JI.

Universal extraction method for gastrointestinal pathogens.

A universal stool extraction method for recovery of nucleic acids (NAs) from gastrointestinal pathogens was developed to support rapid diagnostics for the London 2012 Olympics. The method involved mechanical disruption (bead beating) of the stools, followed by automated extraction and detection using real-time PCR. This method had been used extensively in the Second Infectious Intestinal Disease Study (IID2) for the isolation of NA from bacteria and parasites (and was effective for the robust recovery of Cryptosporidium spp.) but had not been used for enteric viruses. To ensure this method was universally suitable, panels of samples known to contain target bacteria, viruses or parasites were processed in triplicate using the pre-treatment method routinely used for each target and the new extraction method (bead beating). The extracts were tested using real-time PCR and the cycle threshold values were compared. The results from this study showed that bead beating improved yields for the bacterial and parasitic targets and was suitable for the viral targets. The implementation of this universal method should confer cost- and time-saving benefits and streamline the processes required for the characterization of an array of pathogens from faecal samples.

Disease Progression in HIV-1-Infected Viremic Controllers.

BACKGROUND: The mechanism of CD4 T-cell decline in HIV-1 infection is unclear, but the association with plasma viral RNA load suggests viral replication is involved. Indeed, viremic controller patients with low viral RNA loads typically maintain high CD4 T-cell counts. Within a local cohort of 86 viremic controllers, we identify a subgroup (18 "discord controllers") with low CD4 T-cell counts that present clinical uncertainty. The underlying mechanism accounting for CD4 T-cell decline in the face of low or undetectable plasma (RNA) viral load remains unresolved. The objective of this study was to investigate the viral and host immune system dynamics in discord controllers by measuring cellular HIV-1 DNA load, T-cell populations, and T-cell activation markers. METHODS: We compared discord controllers (viral RNA load <2000 copies/mL, <450 CD4 T-cells/mm) with typical controllers (viral RNA load <2000 copies/mL, >450 CD4 T-cells/mm) and progressors (viral RNA load >10,000 copies/mL, <450 CD4 T-cells/mm). We quantified CD4/CD8 naive/central memory/effector memory subsets (CD45RA/RO ± CD62L), activation levels (CD38HLA-DR), and HIV-1 DNA load. RESULTS: Discord controllers resembled progressors showing high viral DNA load, depletion of naive CD4 T-cells, and higher activation in all CD4 T-cell subsets, compared with typical controllers. They were similar to typical controllers with lower CD8 T-cell activation compared with progressors. CONCLUSIONS: Our data are consistent with a relationship between CD4 T-cell activation and disease progression. HIV-1 DNA load may be a better marker of viral replication and disease progression than viral RNA load. Lower level CD8 T-cell activation correlates with low viral RNA load but not with disease progression or viral DNA load.

Comparison of the rate and size of HIV-1 viral load blips with Roche COBAS TaqMan HIV-1 versions 1.0 and 2.0 and implications for patient management.

BACKGROUND: The Roche COBAS TaqMan HIV-1 version 1.0 (v1.0) real-time PCR test detects more low level viral loads (VL) compared to the previous Roche Amplicor version 1.5 assay. Due to under-quantification issues, the Roche TaqMan HIV-1 version 2.0 (v2.0) was introduced in 2009. Controversy remains on differences at the low VL end, where clinical decisions regarding possible viral escape are based. OBJECTIVES: To compare the rate and size of VL blips with v1.0 and v2.0 in virologically suppressed patients and describe the impact of v2.0 on patient management. STUDY DESIGN: A cohort study of HIV-positive patients on antiretroviral therapy with a VL <50 copies/ml at the beginning and end of the study period (July 2008-February 2010). VL blips were compared during two consecutive 9-month periods, initially measured by v1.0, then v2.0. Genotypic resistance testing and treatment switches were described. RESULTS: 1037 of 2584 patients (73.1% male) with median age 43 years were included. 2465 VL samples were measured on v1.0 and 2206 on v2.0. 108 (10.4%) patients had blips on v1.0 (4.4% of samples) compared to 99 (9.5%) patients (4.5% of samples) on v2.0. Median log VL was 1.89 (78 copies/ml) for v1.0 and 2.06 (116 copies/ml) for v2.0 (p=0.002). Further characterisation of 11 samples detected no resistance and no treatment modifications were identified. CONCLUSIONS: TaqMan v1.0 and v2.0 have similar blip rates, while blips are higher with v2.0. This study supports the strategy to increase the threshold of concern for VL blips on v2.0.

Comparative evaluation of the QIAGEN QIAsymphony® SP system and bioMérieux NucliSens easyMAG automated extraction platforms in a clinical virology laboratory.

BACKGROUND: The QIAGEN QIAsymphony(®) SP is an automated system that can process a variety of different sample types for nucleic acid extraction. OBJECTIVES: To compare this system against the bioMérieux NucliSens easyMAG using a range of common clinical sample types. STUDY DESIGN: Nucleic acid extracts were tested on 6 in-house real time viral PCR assays: quantitative cytomegalovirus (CMV); respiratory and enteric multiplex (10 viruses); influenza A H1N1 2009 specific H1 and N1 assays (sH1/N1); herpes simplex virus (HSV) 1, HSV 2 and varicella zoster virus (VZV) multiplex; norovirus genogroups I and II (Noro GI/II) multiplex. RESULTS: Extraction of the clinical sample by either QIAsymphony(®) SP or NucliSens easyMAG gave similar results for each PCR; CMV viral loads, 52 plasma samples had a mean difference (easyMAG-QIAsymphony(®)) of 0.002 log(10)copies/ml (s.d. 0.536), 52 whole blood samples had a mean difference of -0.232 log(10)copies/ml (s.d. 0.490). Concordance for the qualitative assays were; 64/67 (95.5%) for the respiratory and enteric multiplex, all 28 (100%) for the sH1, sN1 and influenza A matrix multiplex, 33/34 (97%) for the HSV1/HSV2/VZV multiplex and all 15 (100%) for the Noro GI/II. Inter- and intra-run variation, determined for a 10-fold dilution series of CMV (5.20-3.20 log(10)copies/ml), was less than 0.63 log(10)copies/ml. CONCLUSIONS: Our evaluation found the performance of the QIAsymphony(®) SP comparable to the NucliSens easyMAG for a range of sample types commonly extracted in a clinical virology laboratory. In total, 331/343 (96.5%) PCR results were concordant on samples extracted by both platforms.

Comparative evaluation of the Seegene Seeplex RV15 and real-time PCR for respiratory virus detection.

Respiratory virus infections contribute substantially both to hospitalizations of young children, and to morbidity in immunocompromised patients such as those with hematological malignancies. Their rapid and accurate diagnosis is essential to patient management. To evaluate the prospective utility of Seeplex® DPO technology in respiratory virus diagnosis, a panel of 99 respiratory samples positive by real-time RT-PCR for one or more viruses was assayed by the Seegene Seeplex® RV12 system. As well as being able to detect all 10 viruses in the real-time RT-PCR system with the exception of enteroviruses, RV12 can also distinguish between the two subgroups of RSV and detect two subgroups of coronaviruses. Seven of the nine viruses in common with the RT-PCR were detected reliably by RV12. Eleven samples RT-PCR-positive for Metapneumovirus and five samples positive for influenza B were not detected by RV12. Seegene developed a second-generation system, RV15, which not only allowed detection of three additional viruses, but also addressed the potential problems with RV12 specificity. To address these concerns, 84 respiratory samples positive for a range of viruses by real-time PCR were assayed with RV15. The results of this evaluation improved significantly upon those seen with RV12. The high throughput capabilities and potential lower technical requirements afforded by the Seeplex® system may offer an alternative to real-time RT-PCR systems.

Extensive human cytomegalovirus (HCMV) genomic DNA in the renal tubular epithelium early after renal transplantation: Relationship with HCMV DNAemia and long-term graft function.

Human cytomegalovirus (HCMV) infection is associated with a series of direct and indirect effects following renal transplantation. However, the presence of HCMV in the kidney and its relationship with acute rejection and long-term graft function remain to be fully elucidated. Sixty-two biopsies derived from 30 renal transplant recipients with signs of clinical rejection were analyzed for HCMV using a sensitive in situ DNA hybridization method. Biopsies were also subjected to staining with anti-C4d antibodies and an anti-caspase 3 antibody to detect humoral rejection and apoptosis, respectively. In 21 patients, serial serum creatinine levels over 5 years of follow-up were analyzed. HCMV DNA was detected in biopsies from 21/30 (70%) of the patients and 32/62 (52%) of the individual biopsies. HCMV DNA was detected early after transplant and was localized to renal tubule epithelial cells but not associated with apoptosis. HCMV DNAemia developed within 2 weeks of detecting HCMV DNA in the biopsy in 53% of patients. Ninety percent of patients experiencing HCMV disease had HCMV DNA in their biopsy. HCMV DNA was equally distributed between patients with or without histological evidence of acute rejection and was detected more frequently in patients with peritubular C4d deposits. Creatinine levels at 12 months post-transplant were significantly higher in patients with HCMV DNA and remained elevated over the 5 years of follow-up. HCMV DNA is frequently detected in renal tubular epithelial cells early after renal transplantation, precedes DNAemia and is associated with poor long-term graft function.

Microarray-based determination of the lytic cascade of human herpesvirus 6B.

The lytic gene expression of several members of the human herpesvirus family has been profiled by using gene-expression microarrays; however, the lytic cascade of roseoloviruses has not been studied in similar depth. Based on the complete DNA genome sequences of human herpesvirus 6 variant A (HHV-6A) and variant B (HHV-6B), we constructed a cDNA microarray containing DNA probes to their predicted open reading frames, plus 914 human genes. Gene-expression profiling of HHV-6B strain Z29 in SupT1 cells over a 60 h time-course post-infection, together with kinetic classification of the HHV-6B genes in the presence of either cycloheximide or phosphonoacetic acid, allowed the placement of HHV-6B genes into defined kinetic classes. Eighty-nine HHV-6B genes were divided into four different expression kinetic classes: eight immediate-early, 44 early, 33 late and four biphasic. Clustering of genes with similar expression profiles implied a shared function, thus revealing possible roles of previously uncharacterized HHV-6B genes.

Human herpesvirus 6 integrates within telomeric regions as evidenced by five different chromosomal sites.

Fluorescent in situ hybridization (FISH) was used to investigate the chromosomal integration sites of human herpesvirus 6 (HHV-6) in phytohemagglutinin-stimulated leukocytes and B lymphocytes from Epstein-Barr virus transformed lymphoblastoid cell lines (LCLs). Five different chromosomal integration sites were found in nine individuals. Only one site was identified in each individual, each site was in the vicinity of the telomeric region and was on either the p or q arm of only one of the two chromosome homologues. The sites were 9q34.3, 10q26.3, 11p15.5, 17p13.3, and 19q 13.4, of which three have not been previously identified. For 9q34.3 the site of integration was further mapped using a locus-specific probe for 9q34.3 together with a pan-telomeric probe and both co-localized with the HHV-6 signal. Similarly an arm-specific telomeric probe for 19q co-localized with the HHV-6 signal. It was therefore concluded that the site of integration is actually within the telomere. The number of viral DNA copies/cell was calculated in blood, LCL cells and hair follicles and was one or more in every case for each of the nine individuals. This result was confirmed by FISH where 100% of cells gave an HHV-6 signal. These findings add to previous reports suggesting that integrated HHV-6 DNA is found in every cell in the body and transmitted vertically. Finally, including our data, worldwide seven different chromosomal sites of HHV-6 integration have now been identified. Large epidemiological studies of chromosomal integration are required to identify further telomeric sites, geographical or racial variation and possible clinical consequences.

Importance of chromosomally integrated HHV-6A and -6B in the diagnosis of active HHV-6 infection.

Human herpesvirus-6 (HHV-6) exists as two closely related variants: A and B. Whereas no disease has been firmly associated with HHV-6A, variant B causes febrile illness in young children and is pathogenic in immunosuppressed transplant recipients. Chromosomally integrated HHV-6 (with either variant A or B) occurs in a minority of people. This phenomenon has the potential to confound the diagnosis of active HHV-6 infection, since chromosomally integrated HHV-6 DNA sequences are inherited through the germline. Therefore, viral DNA is in every nucleated cell in the body and can be found in a range of body fluids including whole blood, serum, plasma and cerebrospinal fluid. There are characteristically very high viral loads in whole blood (> 6 log10 HHV-6 genomes/ml) and serum (5 log10 HHV-6 genomes/ml); these can be used to differentiate individuals with viral chromosomal integration from those with active HHV-6 infection, where viral loads are significantly lower. Increasingly, the polymerase chain reaction (to detect viral nucleic acid) is used for diagnosis; therefore, it is important to exclude HHV-6 chromosomal integration before concluding that there is evidence of active HHV-6 infection.