Genome Characterisation of Invasive Haemophilus influenzae in Pregnancy: The Noticeable Placental Tissue Tropism Is Distributed across the Species Rather Than Linked with Capsulation or Particular Clones.

Pregnancy is associated with a 5-26 times increased risk of invasive Haemophilus influenzae infection and subsequent adverse pregnancy outcomes. Incidence rate and outcome are published in some regions, but the characterisation of bacterial isolates is limited. We performed comparative genomic analyses of isolates from 12 pregnancy-associated cases, cultured from maternal bacteraemia in pregnancy (nine), postpartum bacteraemia (one), neonatal bacteraemia (one), and placental tissue (one). In two bacteraemia cases, identical isolates were also cultured from cervical swabs. Eight cases occurred early in pregnancy (gestational week 7-26), and seven of them resulted in miscarriage or neonatal death. All bacterial genomes were devoid of capsule loci, and they were evenly distributed in the major phylogenetic group I of the species. The conspicuous tropism of H. influenzae for pregnancy and placental tissue is associated with the species rather than specific clonal subtypes.

Treatment effect modifiers in hospitalised patients with COVID-19 receiving remdesivir and dexamethasone.

BACKGROUND: The combined effectiveness of remdesivir and dexamethasone in subgroups of hospitalised patients with COVID-19 is poorly investigated. METHODS: In this nationwide retrospective cohort study, we included 3826 patients with COVID-19 hospitalised between February 2020 and April 2021. The primary outcomes were use of invasive mechanical ventilation and 30-day mortality, comparing a cohort treated with remdesivir and dexamethasone with a previous cohort treated without remdesivir and dexamethasone. We used inverse probability of treatment weighting logistic regression to assess associations with progression to invasive mechanical ventilation and 30-day mortality between the two cohorts. The analyses were conducted overall and by subgroups based on patient characteristics. RESULTS: Odds ratio for progression to invasive mechanical ventilation and 30-day mortality in individuals treated with remdesivir and dexamethasone compared to treatment with standard of care alone was 0.46 (95% confidence interval, 0.37-0.57) and 0.47 (95% confidence interval, 0.39-0.56), respectively. The reduced risk of mortality was observed in elderly patients, overweight patients and in patients requiring supplemental oxygen at admission, regardless of sex, comorbidities and symptom duration. CONCLUSIONS: Patients treated with remdesivir and dexamethasone had significantly improved outcomes compared to patients treated with standard of care alone. These effects were observed in most patient subgroups.

Early intervention with 3BNC117 and romidepsin at antiretroviral treatment initiation in people with HIV-1: a phase 1b/2a, randomized trial.

Attempts to reduce the human immunodeficiency virus type 1 (HIV-1) reservoir and induce antiretroviral therapy (ART)-free virologic control have largely been unsuccessful. In this phase 1b/2a, open-label, randomized controlled trial using a four-group factorial design, we investigated whether early intervention in newly diagnosed people with HIV-1 with a monoclonal anti-HIV-1 antibody with a CD4-binding site, 3BNC117, followed by a histone deacetylase inhibitor, romidepsin, shortly after ART initiation altered the course of HIV-1 infection ( NCT03041012 ). The trial was undertaken in five hospitals in Denmark and two hospitals in the United Kingdom. The coprimary endpoints were analysis of initial virus decay kinetics and changes in the frequency of CD4+ T cells containing intact HIV-1 provirus from baseline to day 365. Secondary endpoints included changes in the frequency of infected CD4+ T cells and virus-specific CD8+ T cell immunity from baseline to day 365, pre-ART plasma HIV-1 3BNC117 sensitivity, safety and tolerability, and time to loss of virologic control during a 12-week analytical ART interruption that started at day 400. In 55 newly diagnosed people (5 females and 50 males) with HIV-1 who received random allocation treatment, we found that early 3BNC117 treatment with or without romidepsin enhanced plasma HIV-1 RNA decay rates compared to ART only. Furthermore, 3BNC117 treatment accelerated clearance of infected cells compared to ART only. All groups had significant reductions in the frequency of CD4+ T cells containing intact HIV-1 provirus. At day 365, early 3BNC117 + romidepsin was associated with enhanced HIV-1 Gag-specific CD8+ T cell immunity compared to ART only. The observed virological and immunological effects of 3BNC117 were most pronounced in individuals whose pre-ART plasma HIV-1 envelope sequences were antibody sensitive. The results were not disaggregated by sex. Adverse events were mild to moderate and similar between the groups. During a 12-week analytical ART interruption among 20 participants, 3BNC117-treated individuals harboring sensitive viruses were significantly more likely to maintain ART-free virologic control than other participants. We conclude that 3BNC117 at ART initiation enhanced elimination of plasma viruses and infected cells, enhanced HIV-1-specific CD8+ immunity and was associated with sustained ART-free virologic control among persons with 3BNC117-sensitive virus. These findings strongly support interventions administered at the time of ART initiation as a strategy to limit long-term HIV-1 persistence.

Tuberculosis incidence and mortality in people living with human immunodeficiency virus: a Danish nationwide cohort study.

OBJECTIVES: To explore changes over time in the epidemiology of tuberculosis (TB) in Denmark in people living with human immunodeficiency virus (HIV) (PLWH). METHODS: In this nationwide, population-based cohort study we included all adult PLWH from the Danish HIV Cohort Study (1995-2017) without previous TB. We estimated TB incidence rate (IR), all-cause mortality rate (MR), associated risk and prognostic factors using Poisson regression. RESULTS: Among 6982 PLWH (73 596 person-years (PY)), we observed 217 TB events (IR 2.9/1000 PY, 95% CI 2.6-3.4: IR 6.7, 95% CI 5.7-7.9 among migrants and IR 1.4, 95% CI 1.1-1.7 among Danish-born individuals; p < 0.001). The IR of concomitant HIV/TB remained high and unchanged over time. The IR of TB diagnosed >3 months after HIV diagnosis declined with calendar time, longer time from HIV diagnosis, and CD4 cell recovery. Independent TB risk factors were African/Asian/Greenland origin (adjusted incidence rate ratio (aIRR) 5.2, 95% CI 3.5-7.6, aIRR 6.5, 95% CI 4.2-10.0, aIRR 7.0, 95% CI 3.4-14.6, respectively), illicit drug use (aIRR 6.9, 95% CI 4.2-11.2), CD4 <200 cells/µL (aIRR 2.7, 95% CI 2.0-3.6) and not receiving antiretroviral therapy (aIRR 3.7, 95% CI 2.5-5.3). Fifty-five patients died (MR 27.9/1000 PY, 95% CI 21.4-36.3), with no improvement in mortality over time. Mortality prognostic factors were Danish-origin (adjusted mortality rate ratio (aMRR) 2.3, 95% CI 1.3-4.3), social burden (aMRR 3.9, 95% CI 2.2-7.0), CD4 <100 cells/µL at TB diagnosis (aMRR 2.6, 95% CI 1.3-4.9), TB diagnosed >3 months after HIV versus concomitant diagnosis (aMRR 4.3, 95% CI 2.2-8.7) and disseminated TB (aMRR 3.3, 95% CI 1.1-9.9). CONCLUSION: Late HIV presentation with concomitant TB remains a challenge. Declining TB rates in PLWH were observed over time and with CD4 recovery, highlighting the importance of early and successful antiretroviral therapy. However, MR remained high. Our findings highlight the importance of HIV and TB screening strategies and treatment of latent TB in high-risk groups.

Incidence of Chronic Obstructive Pulmonary Disease in People With Human Immunodeficiency Virus and Their Parents and Siblings in Denmark.

BACKGROUND: People with human immunodeficiency virus (PWH) may be at increased risk of several respiratory syndromes including chronic obstructive pulmonary disease (COPD). In matched cohort studies, we examined risk factors for COPD in PWH and their parents and siblings compared with population controls. METHODS: Using data from national registries, competing risk regression models were constructed and used to calculate adjusted hazard ratios (aHRs) for COPD. We evaluated the effect of human immunodeficiency virus characteristics, smoking, and educational attainment on COPD incidence in PWH. RESULTS: A total of 226 PWH and 1029 population controls were diagnosed with COPD during 63 661 and 562 171 person-years of follow-up. PWH had increased risk of being diagnosed with COPD compared to controls (aHR, 2.02 [95% confidence interval, 1.75-2.33]). Parents and siblings of PWH were also more likely to be diagnosed with COPD compared to controls. CD4+ T-cell counts were not associated with COPD, but unsuppressed viral replication, smoking status, and educational attainment were associated with COPD in PWH. No COPD diagnoses were registered in PWH with high educational attainment and absence of smoking. CONCLUSIONS: PWH have an increased risk of being diagnosed with COPD, as have their parents and siblings. This seems to be driven primarily by smoking and low socioeconomic status.

Improved Survival Among Hospitalized Patients With Coronavirus Disease 2019 (COVID-19) Treated With Remdesivir and Dexamethasone. A Nationwide Population-Based Cohort Study.

BACKGROUND: There are limited data on outcomes of moderate to severe coronavirus disease 2019 (COVID-19) among patients treated with remdesivir and dexamethasone in a real-world setting. We sought to compare the effectiveness of standard of care (SOC) alone versus SOC plus remdesivir and dexamethasone. METHODS: Two population-based nationwide cohorts of individuals hospitalized with COVID-19 during February through December 2020 were studied. Death within 30 days and need of mechanical ventilation (MV) were compared by inverse probability of treatment weighted (ITPW) logistic regression analysis and shown as odds ratio (OR) with 95% confidence interval (CI). RESULTS: The 30-days mortality rate of 1694 individuals treated with remdesivir and dexamethasone in addition to SOC was 12.6% compared to 19.7% for 1053 individuals receiving SOC alone. This corresponded to a weighted OR of 30-day mortality of 0.47 (95% CI: .38-.57) for patients treated with remdesivir and dexamethasone compared to patients receiving SOC alone. Similarly, progression to MV was reduced (OR 0.36; 95% CI: .29-.46). CONCLUSIONS: Treatment of moderate to severe COVID-19 during June through December that included remdesivir and dexamethasone was associated with reduced 30-day mortality and need of MV compared to treatment in February through May.

Twenty-four-hour fluid administration in emergency department patients with suspected infection: A multicenter, prospective, observational study.

BACKGROUND: To describe 24-hour fluid administration in emergency department (ED) patients with suspected infection. METHODS: A prospective, multicenter, observational study conducted in three Danish hospitals, January 20 to March 2, 2020. We included consecutive adult ED patients with suspected infection (drawing of blood culture and/or intravenous antibiotic administration within 6 hours of admission). Oral and intravenous fluids were registered for 24 hours. PRIMARY OUTCOME: 24-hour total fluid volume. We used linear regression to investigate patient and disease characteristics' effect on 24-hour fluids and to estimate the proportion of the variance in fluid administration explained by potential predictors. RESULTS: 734 patients had 24-hour fluids available: 387 patients had simple infection, 339 sepsis, eight septic shock. Mean total 24-hour fluid volumes were 3656 mL (standard deviation [SD]:1675), 3762 mL (SD: 1839), and 6080 mL (SD: 3978) for the groups, respectively. Fluid volumes varied markedly. Increasing age (mean difference [MD]: 60-79 years: -470 mL [95% CI: -789, -150], +80 years; -974 mL [95% CI: -1307, -640]), do-not-resuscitate orders (MD: -466 mL [95% CI: -797, -135]), and preexisting atrial fibrillation (MD: -367 mL [95% CI: -661, -72) were associated with less fluid. Systolic blood pressure < 100 mmHg (MD: 1182 mL [95% CI: 820, 1543]), mean arterial pressure < 65 mmHg (MD: 1317 mL [95% CI: 770, 1864]), lactate ≥ 2 mmol/L (MD: 655 mL [95% CI: 306, 1005]), heart rate > 120 min (MD: 566 [95% CI: 169, 962]), low (MD: 1963 mL [95% CI: 813, 3112]) and high temperature (MD: 489 mL [95% CI: 234, 742]), SOFA score > 5 (MD: 1005 mL [95% CI: 501, 510]), and new-onset atrial fibrillation (MD: 498 mL [95% CI: 30, 965]) were associated with more fluid. Clinical variables explained 37% of fluid variation among patients. CONCLUSIONS: Patients with simple infection and sepsis received equal fluid volumes. Fluid volumes varied markedly, a variation that was partly explained by clinical characteristics.

First wave of COVID-19 hospital admissions in Denmark: a Nationwide population-based cohort study.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated disease coronavirus disease 2019 (COVID-19), is a worldwide emergency. Demographic, comorbidity and laboratory determinants of death and of ICU admission were explored in all Danish hospitalised patients. METHODS: National health registries were used to identify all hospitalized patients with a COVID-19 diagnosis. We obtained demographics, Charlson Comorbidity Index (CCI), and laboratory results on admission and explored prognostic factors for death using multivariate Cox proportional hazard regression and competing risk survival analysis. RESULTS: Among 2431 hospitalised patients with COVID-19 between February 27 and July 8 (median age 69 years [IQR 53-80], 54.1% males), 359 (14.8%) needed admission to an intensive care unit (ICU) and 455 (18.7%) died within 30 days of follow-up. The seven-day cumulative incidence of ICU admission was lower for females (7.9%) than for males (16.7%), (p < 0.001). Age, high CCI, elevated C-reactive protein (CRP), ferritin, D-dimer, lactate dehydrogenase (LDH), urea, creatinine, lymphopenia, neutrophilia and thrombocytopenia within ±24-h of admission were independently associated with death within the first week in the multivariate analysis. Conditional upon surviving the first week, male sex, age, high CCI, elevated CRP, LDH, creatinine, urea and neutrophil count were independently associated with death within 30 days. Males presented with more pronounced laboratory abnormalities on admission. CONCLUSIONS: Advanced age, male sex, comorbidity, higher levels of systemic inflammation and cell-turnover were independent factors for mortality. Age was the strongest predictor for death, moderate to high level of comorbidity were associated with a nearly two-fold increase in mortality. Mortality was significantly higher in males after surviving the first week.

Low incidence of HCC in chronic hepatitis C patients with pretreatment liver stiffness measurements below 17.5 kilopascal who achieve SVR following DAAs.

BACKGROUND AND AIMS: To evaluate the ability of pretreatment liver stiffness measurements (pLSM) to predict hepatocellular carcinoma (HCC), incident decompensation and all-cause mortality in chronic hepatitis C (CHC) patients who achieved sustained virological response (SVR) after treatment with direct-acting antivirals (DAAs). METHODS: 773 CHC patients with SVR after DAA treatment and no prior liver complications were identified retrospectively. Optimized cut-off of 17.5 kPa for incident HCC was selected by maximum Youden's index. Patients were grouped by pLSM: <10 kPa [reference], 10-17.4 kPa and ≥17.5 kPa. Primary outcomes were incident hepatocellular carcinoma and secondary outcomes were incident decompensated cirrhosis and all-cause mortality, analyzed using cox-regression. RESULTS: Median follow-up was 36 months and 43.5% (336) had cirrhosis (LSM>12.5 kPa). The median pLSM was 11.6 kPa (IQR 6.7-17.8, range 2.5-75) and pLSM of <10 kPa, 10-17.4 kPa and 17.5-75 kPa was seen in 41.5%, 32.2% and 26.3%. During a median follow-up time of 36 months, 11 (1.4%) developed HCC, 14 (1.5%) developed decompensated cirrhosis, and 38 (4.9%) patients died. A pLSM of 17.5 kPa identified patients with a high risk of HCC with a negative predictive value of 98.9% and incidence rate of HCC in the 17.5-75 kPa group of 1.40/100 person years compared to 0.14/100 person years and 0.12/100 person years in the 10-17.4 kPa and <10 kPa groups, p<0.001. CONCLUSION: Pretreatment LSM predicts risk of HCC, decompensation and all-cause mortality in patients with SVR after DAA treatment. Patients with a pLSM <17.5 kPa and no other risk factors for chronic liver disease appear not to benefit from HCC surveillance for the first 3 years after treatment. Longer follow-up is needed to clarify if they can be safely excluded from post treatment HCC screening hereafter.

[Management of Staphylococcus aureus bacteraemia].

In this review, we discuss Staphylococcus aureus bac-teraemia (SAB), which is a frequent and severe condition associated with high morbidity and mortality. Despite these facts, high-quality data on diagnostic approach, treatment and management of SAB remain scarce. Consequently, evidence-based guidelines concerning antibiotic therapy including the optimal choice of antibiotic drug, route of administration and treatment duration are not available. Thus, controlled clinical trials are urgently needed to increase evidence and to potentially improve the outcome for patients with SAB.

Non-AIDS Comorbid Conditions in Persons Living With Human Immunodeficiency Virus (HIV) Compared With Uninfected Individuals 10 Years Before HIV Diagnosis.

We evaluated the impact of non-human immunodeficiency virus (HIV) risk factors by assessing the prevalence of non-AIDS comorbidity up to 10 years before HIV diagnosis in a population-based cohort of persons living with HIV and the background population. These data demonstrates a trend toward increased non-AIDS comorbidity before HIV diagnosis.

Risk of skin cancer in patients with HIV: A Danish nationwide cohort study.

BACKGROUND: The risk of skin cancer in patients with HIV has not been extensively studied. OBJECTIVE: We sought to determine the risk of skin cancer in patients with HIV and compare it with the risk in the background population. METHODS: In a matched, nationwide, population-based cohort study, we compared the risk of skin cancer in 4280 patients with HIV from the Danish HIV cohort study with a background population cohort, according to the level of immunosuppression and route of transmission. Primary outcomes were time to first basal cell carcinoma (BCC), squamous cell carcinoma (SCC), or malignant melanoma. RESULTS: Patients with HIV had an increased risk of BCC and SCC with incident rate ratios of 1.79 (95% confidence interval 1.43-2.22) and 5.40 (95% confidence interval 3.07-9.52), respectively, compared with the background population. We observed no increased risk of malignant melanoma. Low nadir CD4 cell count was associated with an increased risk of SCC. The increased risk of BCC among patients with HIV was restricted to men who had sex with men. LIMITATIONS: This study was observational and included a small number of patients with melanoma. CONCLUSION: Patients with HIV have an increased risk of BCC and SCC. Low nadir, but not current, CD4 cell count as a marker of immunosuppression was associated with an increased risk of SCC.

Acute Appendicitis as the Initial Clinical Presentation of Primary HIV-1 Infection.

We report a case of an adolescent who presented at our emergency department with acute abdominal pain. While the initial diagnosis was acute appendicitis, a secondary and coincidental diagnosis of primary HIV-1 infection was made. Concurrent and subsequent clinical and molecular biology findings form the basis of our argument that primary HIV-1 infection was the cause of acute appendicitis in this individual.

Constrictive pericarditis caused by Cutibacterium (Propionibacterium) acnes: A case report and review of literature.

Constrictive and effusive-constrictive pericarditis are rare cardiac disorders. Only rarely are the conditions caused by purulent infection, and even more infrequently by anaerobe bacteria. We describe a case of constrictive - and effusive-constrictive pericarditis due to Cutibacterium (formerly Propionibacterium) acnes in a 75-year old, immunocompetent and previously healthy patient without any predisposition. The patient was successfully treated with subtotal pericardiectomy and beta-lactam antibacterials. C. acnes was the only infectious agent recovered from samples of cultured pericardial tissue. C. acnes is a microaerophilic, Gram-positive anaerobic bacillus that is a part of the normal flora. In symptomatic patients, however, positive samples should be considered as clinically relevant and not dismissed as contamination. Due to the low virulence, the capability of adherence and biofilm formation of C. acnes, diagnosing C. acnes constrictive pericarditis may be difficult. In the context of compatible symptoms, the incubation time of clinical samples should be prolonged or supplemented by polymerase chain reaction techniques. Parenteral beta-lactam antibacterials are considered the drugs of choice. Severe constrictive and effusive-constrictive pericarditis caused by C. acnes is rare, but can be seen even in otherwise healthy patients. Prolonged incubation time and polymerase chain reaction techniques may be required in order to confirm diagnosis.

Long-Term Mortality in HIV-Infected Individuals 50 Years or Older: A Nationwide, Population-Based Cohort Study.

BACKGROUND: Although the prevalence of HIV-infection among individuals ≥ 50 years of age has increased, the impact of HIV-infection on risk of death in this population remains to be established. Our aim was to estimate long-term mortality among HIV-infected individuals who were 50 years or older, when compared with an individually-matched cohort from the background population. METHODS: Population-based cohort-study including HIV-infected individuals ≥ 50 years, who were alive 1 year after HIV-diagnosis (n = 2440) and a comparison cohort individually-matched by age and gender extracted from the background population (n = 14,588). Cumulative survival was evaluated using Kaplan-Meier method and Mortality Rate Ratios (MRRs) were estimated using Cox Regression Models. Study period 1996-2014. RESULTS: Estimated median survival time from age 50 years for HIV-infected individuals increased from 11.8 years (95% CI: 10.2 to 14.5) during 1996-1999 to 22.8 years (20.0-24.2) in 2006-2014. MRR decreased with increasing age from 3.8 (3.1-4.7) for 50-55 years to 1.6 (1.0-2.6) for 75-80 years. In a cohort of well-treated HIV-infected individuals ≥ 50 years without AIDS-defining events or comorbidity at study inclusion (n = 517). MRR was 1.7 (1.2-2.3) compared with population controls without comorbidity. CONCLUSION: Among HIV-infected individuals estimated median survival time from age 50 years has increased by more than 10 years from 1996-1999 to 2006-2014, but is still substantially lower than in the background population. Even among well-treated HIV-infected individuals ≥ 50 years without comorbidity or AIDS-defining events the estimated median survival time remains lower than in the general population.

[Tungiasis case after a trip to Kenya]. / Et tilfaelde af tungiasis efter rejse i Kenya.

Tungiasis is an ectoparasitic skin disease caused by infestation by the female sand flea, Tunga penetrans. Prevalence in endemic areas may reach 83%, while it is rare in non-endemic areas. However, an increase in international travel to and from the affected regions may lead to a rise in the number of cases in non-endemic countries. We present a Danish case of tungiasis contracted during a trip to Kenya.

Dynamics of proviral HIV-1 184M/V in circulating CD4+ T-cells: a 90 days follow-up study after initiation/switch of HAART.

HIV-1 viral load falls rapidly on initiation of HAART. This phase of decreasing yet substantial viral production in the presence of antiretroviral drugs could generate resistant HIV-1. Whether switching a drug from a failing regime changes the demography of the mutations associated with it in the CD4+ T-cell compartment is not well-defined. We investigated the presence/absence and quantity of 184M and 184V in the CD4+ T-cell compartment of naïve patients initiated to HAART (group I), and patients who shifted to a non-lamivudine therapy (group II). We initiated a prospective 90 d follow-up study of 11 patients to detect and quantity proviral HIV-1 184M and 184V in the CD4+ T-cell compartment with a sensitive real time PCR assay. Results showed that the 184V was not detected in the CD4+ T-cell compartment of any of the 7 naïve patients who started on HAART. Three out of the 4 patients in group II experienced a fall in the percentage of 184V, with reduction to below detection limits in 2 patients. It can be concluded that initiation of HAART does not allow the archiving of the lamivudine associated mutation, 184V, in the CD4+ T-cell compartment. Reduction in the quantity of 184V when therapy is switched to an effective non-lamivudine regime indicates that the mutation in this compartment is dynamic.

HIV-1 reverse transcriptase gene 103K/N and 184M/V combinations in tandem: detection and quantification of HIV-1 populations in the CD45RO+ T-cell compartment by a double-ARMS real-time PCR assay.

BACKGROUND: The proviral HIV-1 reverse transcriptase gene for the 103K/N and 184M/V combinations were studied in tandem. The CD45RO T (memory) cell compartment was investigated. METHODS: A new double-ARMS (amplification refractory mutation system) real-time polymerase chain reaction assay was developed to detect and quantify 4 populations (103K-184M, 103K-184V, 103N-184M, and 103N-184V) in the CD45RO T-cell compartment. Twenty-one patients, 18 lamivudine and efavirenz/nevirapine experienced, were enrolled in a cross-sectional study. RESULTS: None of the mutation combinations were detected in patients on highly active antiretroviral therapy (HAART) (naive at start) with viremia suppression below detection limits. Conversely, all patients exposed to mono- or dual therapy (prior to HAART) carried at least 1 mutation combination regardless of viral load. In 9 patients, 17 mutations were detected in a mosaic of combinations. This study provides definite evidence of the existence of 103N and 184V mutation quasi-populations in tandem, and separately in combination with the wild-type codons, 184M and 103K, in the CD45RO T-cell compartment. CONCLUSIONS: The initiation and continuation of potent antiretroviral therapy effectively hinders the appearance of 103N and 184V mutations alone or in tandem in memory cells. When switching therapies because of failure, caution should be exercised with drugs associated with single-mutation threshold; they can appear in tandem with contemporary resistant virus populations, leading to multidrug resistance.