Applying the moving epidemic method to determine influenza epidemic and intensity thresholds using influenza-like illness surveillance data 2009-2018 in Tunisia

Background

Defining the start and assessing the intensity of influenza seasons are essential to ensure timely preventive and control measures and to contribute to the pandemic preparedness. The present study aimed to determine the epidemic and intensity thresholds of influenza season in Tunisia using the moving epidemic method.

Methods

We applied the moving epidemic method (MEM) using the R Language implementation (package “mem”). We have calculated the epidemic and the different intensity thresholds from historical data of the past nine influenza seasons (2009‐2010 to 2017‐2018) and assessed the impact of the 2009‐2010 pandemic year. Data used were the weekly influenza‐like illness (ILI) proportions compared with all outpatient acute consultations. The goodness of the model was assessed using a cross validation procedure.

Results

The average duration of influenza epidemic during a typical season was 20 weeks and ranged from 11 weeks (2009‐2010 season) to 23 weeks (2015‐2016 season). The epidemic threshold with the exclusion of the pandemic season was 6.25%. It had a very high sensitivity of 85% and a high specificity of 69%. The different levels of intensity were established as follows: low, if ILI proportion is below 9.74%, medium below 12.05%; high below 13.27%; and very high above this last rate.

Conclusions

This is the first mathematically based study of seasonal threshold of influenza in Tunisia. As in other studies in different countries, the model has shown both good specificity and sensitivity, which allows timely and accurate detection of the start of influenza seasons. The findings will contribute to the development of more efficient measures for influenza prevention and control.

Polymorphism of ftsI gene in Haemophilus influenzae and emergence of cefotaxime resistance in two Tunisian hospitals

The decreased affinity to β-lactams in Haemophilus influenzae is usually caused by specific alterations in penicillin-binding protein 3 due to varieties of substitutions in ftsI gene. This study aimed to characterize the polymorphism of ftsI gene in 19 H. influenzae strains, isolated between 2014 and 2016 (different resistance phenotypes to β-lactams (n = 9) and susceptible strains (n = 10) used for comparative purposes).

All strains were characterized for capsular type by PCR and agglutination tests and for β-lactam resistance by amplification and sequencing of ftsI. Biotyping and clonality were performed by API-NH and pulsed-field gel electrophoresis, respectively.

Four strains were β-lactamase-negative ampicillin-resistant and five were β-lactamase-positive clavulanic-acid-resistant. One strain from each group was resistant to cefotaxime. Our isolates belonged mainly to biotype IV and I and were non-typeable and genetically unrelated. According to mutation profiles of their ftsI, strains were classified as group I (n = 3), group II (n = 4), group–III–like (n = 1) and group III (n = 1). All group II strains were further classified as subgroup IIb, except for one strain, which harboured a new mutation (N422I). Ampicillin MICs of β-lactamase-negative ampicillin-resistant strains were 6 to 12 times the MICs of susceptible strains. Only bla_TEM-1 was detected in β-lactamase-positive clavulanic-acid-resistant strains, and was responsible for high MICs for ampicillin (>256 mg/L), whatever the ftsI mutational resistance group.

The emergence of cefotaxime-resistant isolates in our country is a matter of concern and requires strict surveillance and rationalization of antibiotic use to preserve these molecules.

Evaluation of the influenza-like illness surveillance system in Tunisia, 2012-2015

BACKGROUND

This study was initiated to evaluate, for the first time, the performance and quality of the influenza-like illness (ILI) surveillance system in Tunisia.

METHODS

The evaluation covered the period of 2012-2015 and used different data sources to measure indicators related to data quality and completeness, representativeness, timeliness, simplicity, acceptability, flexibility, stability and utility.

RESULTS

During the evaluation period, 485.221 ILI cases were reported among 6.386.621 outpatients at 268 ILI sentinel sites. To conserve resources, cases were only enrolled and tested for influenza during times when the number of patients meeting the ILI case definition exceeded 7% (10% after 2014) of the total number of outpatients for the week. When this benchmark was met, five to 10 patients were enrolled and sampled by nasopharyngeal swabs the following week. In total, The National Influenza Center (NIC) received 2476 samples, of which 683 (27.6%) were positive for influenza. The greatest strength of the system was its representativeness and flexibility. The timeliness of the data and the acceptability of the surveillance system performed moderately well; however, the utility of the data and the stability and simplicity of the surveillance system need improvement. Overall, the performance of the Tunisian influenza surveillance system was evaluated as performing moderately well for situational awareness in the country and for collecting representative influenza virologic samples.

CONCLUSIONS

The influenza surveillance system in Tunisia provided pertinent evidence for public health interventions related to influenza situational awareness. To better monitor influenza, we propose that ILI surveillance should be limited to sites that are currently performing well and the quality of data collected should be closely monitored and improved.

Nosocomial outbreak of imipenem-resistant Pseudomonas aeruginosa producing VIM-2 metallo-β-lactamase in a kidney transplantation unit

Background

Twenty four non replicate imipenem resistant P. aeruginosa were isolated between January and November 2008, in the kidney transplantation unit of Charles Nicolle Hospital of Tunis (Tunisia). This study was conducted in order to establish epidemiological relationship among them and to identify the enzymatic mechanism involved in imipenem resistance.

Methods

Analysis included antimicrobial susceptibility profile, phenotypic (imipenem-EDTA synergy test) and genotypic detection of metallo-β-lactamase (MBL) (PCR), O-serotyping and pulsed-field gel electrophoresis.

Results

All strains showed a high level of resistance to all antimicrobials tested except to colistin. The presence of MBL showed concordance between phenotypic and genotypic methods. Sixteen isolates were identified as VIM-2 MBL-producers and 13 of them were serotype O4 and belonged to a single pulsotype (A).

Conclusions

This study describes an outbreak of VIM-2-producing P. aeruginosa in a kidney transplantation unit. Clinical spread of bla_VIM-2 gene is a matter of great concern for carbapenem resistance in Tunisia.

Time of onset, viral load, relapse, and duration of active cytomegalovirus infection in bone marrow transplant outcomes

OBJECTIVES

Active cytomegalovirus infection remains a major problem for bone marrow transplant recipients. If not quickly diagnosed and treated, it can evolve into cytomegalovirus disease, which represents a life-threatening complication. In this work, we sought to evaluate the interactions between clinical complications after bone marrow transplant and factors associated with active cytomegalovirus infection.

MATERIALS AND METHODS

We evaluated 91 allogeneic bone marrow transplant recipients (35 female, 56 male; median age, 20 years; age range, 3-47 years) for malignant and nonmalignant hematologic diseases. Active cytomegalovirus infection was monitored using pp65 cytomegalovirus antigenemia and a semiquantitative cytomegalovirus polymerase chain reaction. Cytomegalovirus end-organ disease was defined as an association between compatible signs and symptoms (dyspnea, hypoxia, and diarrhea) and detection of cytomegalovirus (>or= 2,000 cytomegalovirus genome copies/mL) by hybrid capture assay in tissue biopsy. Variables were compared using the chi-square and Fisher exact tests. Time of death after bone marrow transplant was plotted using the Kaplan-Meier method. A Cox regression model was used for multivariate survival analysis with 95% confidence limits.

RESULTS

Sixty-four patients experienced active cytomegalovirus infection, 26 had acute graft-versus-host disease, and 11 had cytomegalovirus diseases. The overall survival rate at 4 years was 83.52%. On multivariate analyses, cytomegalovirus disease (hazard ratio = 15.9, P = .001) and age older than 18 years (hazard ratio = 8, P = .18) were the only independent negative prognostic factors for overall survival. Occurrence of acute graft-versus-host disease was increased by early active cytomegalovirus infection (P = .03) and represents a significant factor for active cytomegalovirus infection recurrence (P = .01). Viral load as quantified by antigenemia and cytomegalovirus DNA in the patients' peripheral blood leukocytes was significantly associated with clinical complications.

CONCLUSIONS

Active cytomegalovirus infection interacts significantly in several ways with graft-versus-host disease and others infections. Acute graft-versus-host disease increases the chances of a poor outcome, especially of acquiring cytomegalovirus disease. Cytomegalovirus disease constitutes a significant independent risk factor for death after bone marrow transplant.

Implications of the International Health Regulations (2005) for communicable disease surveillance systems: Tunisia's experience

BACKGROUND

In May 2005, the revised International Health Regulations, known as IHR (2005), were adopted in response to the evolving nature of communicable diseases (CD) and the rapid increase in global trade and travel. CD surveillance is an integral part of a country's core requirements under the regulations.

METHODS

The implications of these requirements were assessed as part of a review of the national CD surveillance system of Tunisia using a qualitative methodology of strengths, weaknesses, opportunities and threats (SWOT).

RESULTS

Tunisia is some way towards meeting the requirements of IHR (2005) while some specific areas that need to be addressed are highlighted for improvement: standardization of surveillance documents, strengthening the role of the laboratory in surveillance, increased human resources and training.

CONCLUSIONS

Tunisia's experience can offer some lessons to other countries in this process. While meeting the capacity obligations of IHR (2005) requires investment and commitment, this investment will enable countries to better protect themselves against public health emergencies arising within their borders and threatening from elsewhere in the world.