A Novel Anti-nucleocapsid Antibody Avidity Method for Identifying SARS-CoV-2 Reinfections.

Detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfections is challenging with current serology assays and is further complicated by the marked decrease in routine viral testing practices as viral transmission increased during Omicron. Here, we provide proof-of-principle that high-avidity anti-nucleocapsid (N) antibodies detects reinfections after a single infection with higher specificity (85%; 95% confidence interval [95% CI], 80%-90%) compared to anti-N antibody levels (72%; 95% CI, 66%-79%) in a vaccinated cohort. This method could be used to retroactively investigate the epidemiology and incremental long-term health consequences of SARS-CoV-2 reinfections.

Chronic active Epstein-Barr virus infection with reinfection of SARS-CoV-2: a case report.

We describe the case of a 57-year-old male with jaundice, abdominal distension and fatigue. He was diagnosed as chronic active Epstein-Barr virus infection (CAEBV) due to intermittent elevated liver enzymes, hepatosplenomegaly and pancytopenia, with persistent positive of EBV biomarkers in blood and also positive in liver tissue. The patient was reinfected by SARS-CoV-2 within 2 months companied with CAEBV. The patient's second infection with SARS-CoV-2 led to the aggravated liver dysfunction with pneumonia and re-admission. After receiving symptomatic treatment, the patient showed significantly improvement of symptoms with partially restoration of liver function. After discharge, the patient's health status continued to deteriorate and eventually died. The instances of SARS-CoV-2 co-infection with the original chronic virus are not uncommon, but the exact mechanism of EBV and SARS-CoV-2 coinfection and the relationship between them are still unclear. Since co-infection of SARS-CoV-2 with original chronic virus might affect each other and lead disease aggravated and complicated, it is necessary to differentiate in the diagnosis of disease and it is important to be aware of the re-infection signs of SARS-CoV-2 in people with chronic virus infection diseases, as well as the risk of co-infection of SARS-CoV-2 with other viruses.

Distinguishing Severe Acute Respiratory Syndrome Coronavirus 2 Persistence and Reinfection: A Retrospective Cohort Study.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection is poorly understood, partly because few studies have systematically applied genomic analysis to distinguish reinfection from persistent RNA detection related to initial infection. We aimed to evaluate the characteristics of SARS-CoV-2 reinfection and persistent RNA detection using independent genomic, clinical, and laboratory assessments. METHODS: All individuals at a large academic medical center who underwent a SARS-CoV-2 nucleic acid amplification test (NAAT) ≥45 days after an initial positive test, with both tests between 14 March and 30 December 2020, were analyzed for potential reinfection. Inclusion criteria required having ≥2 positive NAATs collected ≥45 days apart with a cycle threshold (Ct) value <35 at repeat testing. For each included subject, likelihood of reinfection was assessed by viral genomic analysis of all available specimens with a Ct value <35, structured Ct trajectory criteria, and case-by-case review by infectious diseases physicians. RESULTS: Among 1569 individuals with repeat SARS-CoV-2 testing ≥45 days after an initial positive NAAT, 65 (4%) met cohort inclusion criteria. Viral genomic analysis characterized mutations present and was successful for 14/65 (22%) subjects. Six subjects had genomically supported reinfection, and 8 subjects had genomically supported persistent RNA detection. Compared to viral genomic analysis, clinical and laboratory assessments correctly distinguished reinfection from persistent RNA detection in 12/14 (86%) subjects but missed 2/6 (33%) genomically supported reinfections. CONCLUSIONS: Despite good overall concordance with viral genomic analysis, clinical and Ct value-based assessments failed to identify 33% of genomically supported reinfections. Scaling-up genomic analysis for clinical use would improve detection of SARS-CoV-2 reinfections.

Results from a systematic programme of evaluating COVID-19 reinfection cases in the early phase of the pandemic, Singapore.

OBJECTIVES: The objectives of this study were to describe the coronavirus disease caused by SARS-CoV-2 (COVID-19) reinfection evaluation algorithm used in the early phase of the pandemic in Singapore and analyze the clinical and laboratory characteristics of the cases evaluated. METHODS: We performed a retrospective case-control analysis including all COVID-19 cases evaluated for possible reinfection under the local COVID-19 reinfection evaluation programme between 1 June 2020-30 June 2021. Whole genome sequencing (WGS) was used as confirmatory testing. We compared all reinfection ("RI") cases against those who were evaluated but eventually assessed not to be reinfection ("non-RI"). RESULTS: There were 74 possible reinfection cases evaluated through the programme, of which 32 were subsequently classified as RI. There was strong statistical evidence that RI cases had a longer interval between 1st and 2nd episode (mean 297 days; 95%-confidence interval (CI) 267-327) compared to non-RI cases (mean 186 days; 95%-CI 144-228). The cycle threshold (Ct) value of initial polymerase chain rection (PCR) at 2nd episode was also found to be significantly lower in RI cases (mean 23; 95%-CI 20-26) compared to non-RI cases (mean 34; 95%-CI 32-36). There was no significant difference in the proportion of individuals who had fever, acute respiratory symptoms or asymptomatic in both groups. Delta and beta variants were most commonly identified from WGS and provide indication of re-infection as these were not 'wild-type' and were not circulating during the time period of the index infection. CONCLUSIONS: Using a combination of serologic, microbiologic and genomic criteria to evaluate possible reinfection cases is useful and can provide a framework for evaluation that may be modified for future similar situations.

Reconciling Egg- and Antigen-Based Estimates of Schistosoma mansoni Clearance and Reinfection: A Modeling Study.

BACKGROUND: Despite decades of interventions, 240 million people have schistosomiasis. Infections cannot be directly observed, and egg-based Kato-Katz thick smears lack sensitivity, affected treatment efficacy and reinfection rate estimates. The point-of-care circulating cathodic antigen (referred to from here as POC-CCA+) test is advocated as an improvement on the Kato-Katz method, but improved estimates are limited by ambiguities in the interpretation of trace results. METHOD: We collected repeated Kato-Katz egg counts from 210 school-aged children and scored POC-CCA tests according to the manufacturer's guidelines (referred to from here as POC-CCA+) and the externally developed G score. We used hidden Markov models parameterized with Kato-Katz; Kato-Katz and POC-CCA+; and Kato-Katz and G-Scores, inferring latent clearance and reinfection probabilities at four timepoints over six-months through a more formal statistical reconciliation of these diagnostics than previously conducted. Our approach required minimal but robust assumptions regarding trace interpretations. RESULTS: Antigen-based models estimated higher infection prevalence across all timepoints compared with the Kato-Katz model, corresponding to lower clearance and higher reinfection estimates. Specifically, pre-treatment prevalence estimates were 85% (Kato-Katz; 95% CI: 79%-92%), 99% (POC-CCA+; 97%-100%) and 98% (G-Score; 95%-100%). Post-treatment, 93% (Kato-Katz; 88%-96%), 72% (POC-CCA+; 64%-79%) and 65% (G-Score; 57%-73%) of those infected were estimated to clear infection. Of those who cleared infection, 35% (Kato-Katz; 27%-42%), 51% (POC-CCA+; 41%-62%) and 44% (G-Score; 33%-55%) were estimated to have been reinfected by 9-weeks. CONCLUSIONS: Treatment impact was shorter-lived than Kato-Katz-based estimates alone suggested, with lower clearance and rapid reinfection. At 3 weeks after treatment, longer-term clearance dynamics are captured. At 9 weeks after treatment, reinfection was captured, but failed clearance could not be distinguished from rapid reinfection. Therefore, frequent sampling is required to understand these important epidemiological dynamics.

Population-level estimates of hepatitis C reinfection post scale-up of direct-acting antivirals among people who inject drugs.

BACKGROUND & AIMS: Scale-up of highly effective direct-acting antivirals (DAAs) for HCV among people who inject drugs (PWID) in Scotland has led to a reduction in the prevalence of viraemia in this population. However, the extent of reinfection among those treated with DAAs remains uncertain. We estimated HCV reinfection rates among PWID in Scotland by treatment setting, pre- and post-introduction of DAAs, and the potential number of undiagnosed reinfections resulting from incomplete follow-up testing. METHODS: Through linkage of national clinical and laboratory HCV data, a retrospective cohort of PWID who commenced treatment between 2000-2018 and achieved a sustained virological response (SVR) were followed up for reinfection to December 2019. Reinfection was defined as a positive HCV antigen or RNA test. RESULTS: Of 5,686 SVRs among 5,592 PWID, 4,126 (73%) had an HCV RNA or antigen test post-SVR. Of those retested, we identified 361 reinfections (3.9/100 person-years [PY]). The reinfection rate increased from 1.5/100 PY among PWID treated in 2000-2009 to 8.8/100 PY in 2017-2018. The highest reinfection rates were observed among those treated in prison (14.3/100 PY) and community settings (9.5/100 PY). Among those treated in the DAA era (2015-2018), 68% were tested within the first year post-SVR but only 30% in the second year; while 169 reinfections were diagnosed in follow-up, an estimated 200 reinfections (54% of the estimated total) had gone undetected. CONCLUSIONS: HCV reinfection rates among PWID in Scotland have risen alongside the scale-up of DAAs and broadened access to treatment for those at highest risk, through delivery in community drug services. Promotion of HCV testing post-SVR among PWID is essential to ensure those reinfected are identified and retreated promptly. LAY SUMMARY: Increased rates of hepatitis C reinfection in Scotland were observed following the rapid scale-up of highly effective direct-acting antiviral (DAA) treatments among people who inject drugs. This demonstrates that community-based treatment pathways are reaching high-risk groups, regarded vital in efforts to eliminate the virus. However, we estimate that less than half of reinfections have been detected in the DAA era because of inadequate levels of retesting beyond the first year following successful treatment. Sustained efforts that involve high coverage of harm reduction measures and high uptake of annual testing are required to ensure prompt diagnosis and treatment of those reinfected if the goals of elimination are to be met.

Occupational risk of SARS-CoV-2 infection and reinfection during the second pandemic surge: a cohort study.

OBJECTIVES: This cohort study including essential workers, assessed the risk and incidence of SARS-CoV-2 infection during the second surge of COVID-19 according to baseline serostatus and occupational sector. METHODS: Essential workers were selected from a seroprevalence survey cohort in Geneva, Switzerland and were linked to a state centralised registry compiling SARS-CoV-2 infections. Primary outcome was the incidence of virologically confirmed infections from serological assessment (between May and September 2020) to 25 January 2021, according to baseline antibody status and stratified by three predefined occupational groups (occupations requiring sustained physical proximity, involving brief regular contact or others). RESULTS: 10 457 essential workers were included (occupations requiring sustained physical proximity accounted for 3057 individuals, those involving regular brief contact, 3645 and 3755 workers were classified under 'Other essential occupations'). After a follow-up period of over 27 weeks, 5 (0.6%) seropositive and 830 (8.5%) seronegative individuals had a positive SARS-CoV-2 test, with an incidence rate of 0.2 (95% CI 0.1 to 0.6) and 3.2 (95% CI 2.9 to 3.4) cases per person-week, respectively. Incidences were similar across occupational groups. Seropositive essential workers had a 93% reduction in the hazard (HR of 0.07, 95% CI 0.03 to 0.17) of having a positive test during the follow-up with no significant between-occupational group difference. CONCLUSIONS: A 10-fold reduction in the hazard of being virologically tested positive was observed among anti-SARS-CoV-2 seropositive essential workers regardless of their sector of occupation, confirming the seroprotective effect of a previous SARS-CoV2 exposure at least 6 months after infection.

Possible Cases of SARS-CoV-2 Reinfection In Pekanbaru, Indonesia.

Confirmed and possible reinfection cases of SARS-CoV-2 have been reported from various countries. Here we present two cases of possible SARS-CoV-2 reinfection in Pekanbaru, Indonesia. A 26 years old female and a 27 years old male healthcare workers were first confirmed by PCR with high Ct-value (>35) while presenting no or mild symptoms, respectively. In more than one month since the last negative test results, both patients developed typical COVID-19 symptoms; fever and anosmia. RT-PCR results for SARS-CoV-2 were positive with Ct-value less than 30. The timeframe between 1st and 2nd episode, negative test result between episodes, and epidemiological risk factor strengthened the possibility of reinfection. However, we did not have whole genome sequence (WGS) or viral viability data to further confirm reinfection with different viable virus. The requirement of viral WGS data to confirm true reinfection cases calls for investment in whole genome sequencing platform in public health laboratories. We encourage standardized definition of SARS-CoV-2 reinfection case in order to be able to investigate and observe such cases.

Proper Assignation of Reactivation in a COVID-19 Recurrence Initially Interpreted as a Reinfection.

A 77-year-old man (case R) with previous diagnosis of a mild COVID-19 episode was hospitalized 35 days later. On day 23 postadmission, he developed a second COVID-19 episode, now severe, and finally died. Initially, case R's COVID-19 recurrence was interpreted as a reinfection due to the exposure to a SARS-CoV-2 RT-PCR-positive roommate. However, whole-genome sequencing indicated that case R's recurrence corresponded to a reactivation of the strain involved in his first episode. Case R's reactivation had major consequences, leading to a more severe episode, and causing subsequent transmission to another 2 hospitalized patients, 1 of them with fatal outcome.

Respiratory Viral Shedding in Healthcare Workers Reinfected with SARS-CoV-2, Brazil, 2020.

We documented 4 cases of severe acute respiratory syndrome coronavirus 2 reinfection by non-variant of concern strains among healthcare workers in Campinas, Brazil. We isolated infectious particles from nasopharyngeal secretions during both infection episodes. Improved and continued protection measures are necessary to mitigate the risk for reinfection among healthcare workers.

Persistence of symptoms after improvement of acute COVID19 infection, a longitudinal study.

With the number of coronavirus disease 2019 (COVID-19) infected patients increasing all over the world, a large number of survivors have reported changes in their quality of life or experienced re-infection. So, we aimed to detect the percentage, type, and risk factors of persistent symptoms after improvement from acute COVID-19 infection and to detect the percentage of COVID-19 re-infection and degree of severity of the second infection. One hundred seventy-two (59 male, 113 female) patients who tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were followed up via mobile phone every 2 months for 8 to 10 months. After recovery, 105 patients (61%) (30 male, 75 female) reported one or more COVID-19 persistent symptoms. Fatigue, dyspnea, and depression were the most common persistent symptoms representing 37.3%, 22%, 22%, respectively. We found that age was independently related to the persistence of symptoms. During the follow-up, six females (3.5%) had laboratory-confirmed COVID-19 re-infection. Their mean age was 35.7 ± 11 years. The mean interval from the complete recovery of the first infection to the onset of the second one was 53 ± 22.2 days and ranged from 30 to 90 days. The second infection was milder in severity than the first infection in 83.33% of cases. There was a high percentage of patients who complained of persistent symptoms after recovery from COVID-19. Fatigue and headache were the most common persistent symptoms. Age was considered a risk factor for persistent symptoms. Re-infection with SARS-CoV-2 can occur after recovery.

Suspected Recurrent SARS-CoV-2 Infections Among Residents of a Skilled Nursing Facility During a Second COVID-19 Outbreak - Kentucky, July-November 2020.

Reinfection with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is believed to be rare (1). Some level of immunity after SARS-CoV-2 infection is expected; however, the evidence regarding duration and level of protection is still emerging (2). The Kentucky Department for Public Health (KDPH) and a local health department conducted an investigation at a skilled nursing facility (SNF) that experienced a second COVID-19 outbreak in October 2020, 3 months after a first outbreak in July. Five residents received positive SARS-CoV-2 reverse transcription-polymerase chain reaction (RT-PCR) test results during both outbreaks. During the first outbreak, three of the five patients were asymptomatic and two had mild symptoms that resolved before the second outbreak. Disease severity in the five residents during the second outbreak was worse than that during the first outbreak and included one death. Because test samples were not retained, phylogenetic strain comparison was not possible. However, interim period symptom resolution in the two symptomatic patients, at least four consecutive negative RT-PCR tests for all five patients before receiving a positive test result during the second outbreak, and the 3-month interval between the first and the second outbreaks, suggest the possibility that reinfection occurred. Maintaining physical distance, wearing face coverings or masks, and frequent hand hygiene are critical mitigation strategies necessary to prevent transmission of SARS-CoV-2 to SNF residents, a particularly vulnerable population at risk for poor COVID-19-associated outcomes.* Testing, containment strategies (isolation and quarantine), and vaccination of residents and health care personnel (HCP) are also essential components to protecting vulnerable residents. The findings of this study highlight the importance of maintaining public health mitigation and protection strategies that reduce transmission risk, even among persons with a history of COVID-19 infection.

Predictors of severe symptomatic laboratory-confirmed SARS-CoV-2 reinfection.

OBJECTIVE: The aim of the study was to evaluate factors predicting severe symptomatic laboratory-confirmed (via Reverse transcription polymerase chain reaction, RT-PCR polymerase chain reaction) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection. STUDY DESIGN: This is a nationwide retrospective cohort study that was conducted in Mexico. METHODS: Data from 258 reinfection cases (at least 28 days between both episodes onset) were analyzed. We used risk ratios (RRs) and 95% confidence intervals (CIs) to evaluate predictors of severe (dyspnea requiring hospital admission) secondary SARS-CoV-2 infection. RESULTS: The risk of severe disease was 14.7%, and the observed overall fatality rate was 4.3%. Patients with more serious primary disease were more likely to develop severe symptoms (39.5% vs. 5.5%, P < 0.001) during reinfection. In multiple analysis, factors associated with an increased risk of severe symptomatic SARS-CoV-2 reinfection were increasing age (RRper year = 1.007, 95% CI = 1.003-1.010), comorbidities (namely, obesity [RR = 1.12, 95% CI = 1.01-1.24], asthma [RR = 1.26, 95% CI = 1.06-1.50], type 2 diabetes mellitus [RR = 1.22, 95% CI = 1.07-1.38]), and previous severe laboratory-confirmed coronavirus disease 2019 (RR = 1.20, 95% CI = 1.03-1.39). CONCLUSIONS: To the best of our knowledge, this is the first study evaluating disease outcomes in a large set of laboratory-positive cases of symptomatic SARS-CoV-2 reinfection, and factors associated with illness severity were characterized. Our results may contribute to the current knowledge of SARS-CoV-2 pathogenicity and to identify populations at increased risk of a poorer outcome after reinfection.

Serologic Responses in Healthy Adult with SARS-CoV-2 Reinfection, Hong Kong, August 2020.

In March 2020, mild signs and symptoms of coronavirus disease developed in a healthy 33-year-old man in Hong Kong. His first infection did not produce virus neutralizing antibodies. In August, he had asymptomatic reinfection, suggesting that persons without a robust neutralizing antibody response might be at risk for reinfection.

Retest positive for SARS-CoV-2 RNA of "recovered" patients with COVID-19: Persistence, sampling issues, or re-infection?

"Retest Positive" for severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) from "recovered" coronavirus disease-19 (COVID-19) has been reported and raised several important questions for this novel coronavirus and COVID-19 disease. In this commentary, we discussed several questions: (a) Can SARS-CoV-2 re-infect the individuals who recovered from COVID-19? This question is also associated with other questions: whether or not SARS-CoV-2 infection induces protective reaction or neutralized antibody? Will SARS-CoV-2 vaccines work? (b) Why could some recovered patients with COVID-19 be re-tested positive for SARS-CoV-2 RNA? (c) Are some recovered pwith atients COVID-19 with re-testing positive for SARS-CoV-2 RNA infectious? and (d) How should the COVID-19 patients with retest positive for SARS-CoV-2 be managed?

Chlamydia trachomatis and Neisseria gonorrhoeae Retesting and Reinfection Rates in New Zealand Health Care Settings: Implications for Sexually Transmitted Infection Control.

BACKGROUND: Reinfection with chlamydia or gonorrhea is common and can lead to significant reproductive health complications so testing for reinfection after treatment is recommended. This study described retesting and reinfection rates in regions of New Zealand with higher-than-average population rates of chlamydia. METHODS: This retrospective cohort study analyzed chlamydia and gonorrhea testing data from 2 laboratories providing community testing services for 4 higher-rate regions in the North Island of New Zealand. Three years of data were obtained (2015-2017) to include a minimum of 6-month follow-up for all individuals. Retesting and reinfection rates between 6 weeks and 6 months of a positive result were calculated, and time to retesting was plotted using Kaplan-Meier curves. Logistic regression modeling was used to determine the odds of retesting (outcome 1) and reinfection (outcome 2) between 6 weeks and 6 months of follow-up. RESULTS: Overall, 34% (3151/9241) of the cohort was retested within the recommended period, of whom 21% retested positive. Significant differences were observed in the odds of retesting by sex, age band, ethnic group, clinic type, and region (P < 0.01). The odds of a subsequent positive on retesting within 6 months differed significantly by sex, age band, and ethnic group (P < 0.01). CONCLUSIONS: These findings reflect substantial gaps in the delivery of best-practice sexually transmitted infection management in New Zealand. There is a clear need to prioritize the implementation of clinic-level processes to support clinicians in the routine delivery of best-practice sexual health care. These should include routine provision of patient advice about retesting and strategies to promote timely and equitable access to retesting.

The QuantiFERON Monitor® assay is predictive of infection post allogeneic hematopoietic cell transplantation.

INTRODUCTION: Following allogeneic hematopoietic stem cell transplantation (alloHCT), excessive immunosuppression can be complicated by infection, while inadequate immunosuppression can result in graft-vs-host disease (GVHD). An accurate method to assess overall immune status post HCT is lacking. The QuantiFERON Monitor® (QFM) assay measures interferon gamma (IFN-γ) release from whole blood following incubation with both innate (Toll-like receptor 7, TLR7) and adaptive (CD3 antibody) stimulants and may result in a more complete assessment of the immune system. METHODS: Whole blood samples were prospectively collected from alloHCT recipients at conditioning followed by days 10, 30, 60, 90, 120, and 180 post-transplant and assayed by the QFM test. IFN-γ levels were correlated to time post HCT and episodes of infection and GVHD. RESULTS: Forty patients were enrolled in the study (68% male; median age 47 years; 58% matched related donors, 42% unrelated; 33% myeloablative). Post-stimulation IFN-γ levels rose steadily over the first 180 days post transplantation. IFN-γ levels were significantly lower in those with active infection compared to those without during the neutropenic period (P < .001). The assay was predictive of CMV reactivation (VL > 1000 copies/mL) post alloHCT (P = .001). CONCLUSION: This is a promising assay to demonstrate immune recovery and predict risk of infection after alloHCT and may allow tailoring of immunosuppression, antimicrobial treatment, and prophylaxis.

Utility of rapid plasmin reagin titres in assessing treatment response and re-infection for infectious syphilis.

Background The rapid plasma reagin (RPR) assay is commonly used as a surrogate marker of infectious syphilis, but is non-specific, slow to change and variable in its rate of decline post treatment. METHODS: Within an urban sexual health service testing predominantly men who have sex with men, a file review of RPR changes was undertaken in all subjects who had a dilution level of ≥1:4, between January 2015 to the end of December 2018. RESULTS: Overall, 248 cases of infectious syphilis were identified in 215 subjects (165 HIV seropositive, 50 HIV seronegative). Among unique-subject cases with follow-up RPR recorded, seroreversion to a non-reactive titre was achieved in only 42.3% (71/168) cases at a median of 235 days (interquartile range: 138-348 days) and was significantly less likely if patients had HIV infection (P = 0.02), late latent syphilis (P = 0.003) or a subsequent syphilis infection (P < 0.0001). Having HIV infection (P = 0.03) or a subsequent episode of syphilis (P = 0.01) were associated with a lower likelihood of documented cure. CONCLUSIONS: The slow decay in RPR titres post therapy and the inability of a significant number of subjects to achieve a non-reactive result over time makes RPR a poor test for assessing the adequacy of treatment or in diagnosing re-infection, especially in populations having repeated and frequent risk exposures. As the number of syphilis cases continue to climb, better tests that accurately assess pathogen presence are urgently needed.

Recurrent mucocutaneous infections caused by PVL-positive Staphylococcus aureus strains: a challenge in clinical practice.

BACKGROUND: Recurrent mucocutaneous infections caused by PVL-positive Staphylococcus (S.) aureus strains represent an increasing problem in Germany. Although there have been several outbreaks at day care centers and in urban communities in recent years, there are currently no diagnostic algorithms or treatment recommendations for these particular infections in Germany. METHODS: We performed a literature search in the PubMed/MEDLINE database with the goal of developing an algorithm for diagnosis and treatment of these infections. National and international recommendations were also considered. RESULTS: Panton-Valentine leukocidin (PVL) is a pore-forming protein produced by certain S. aureus strains. Both methicillin-susceptible (MSSA) and methicillin-resistant S. aureus (MRSA) strains may carry the lukS-lukF gene responsible for PVL production. The clinical presentation of infections caused by PVL-positive S. aureus ranges from isolated recurrent abscesses to extensive furunculosis. Despite adequate treatment of primary infections, approximately 40 % of patients develop recurrent disease. The choice of treatment regimen is guided by the clinical presentation of the infection. In addition, some scientific literature recommends bacteriological screening of patients and their contacts, followed by decolonization of affected individuals. CONCLUSIONS: The present article focuses on the pathogenesis and risk factors of recurrent mucocutaneous infections caused by PVL-positive S. aureus strains and proposes a diagnostic and therapeutic algorithm for optimal patient care.