Biomedical subjects

F Carrat

Publications and source records attributed to F Carrat.

At least 19 recordsLinked to original sources

PubMed2006

Repeated influenza vaccination of healthy children and adults: borrow now, pay later?

A growing number of publications are recommending annual influenza vaccination of healthy children and adults. However, the long-term consequences of repeated influenza vaccination are unknown. We used a simple model of recurrent influenza infection to assess the likely impact of various repeated influenza vaccination scenarios. The model was based on a Markovian framework and was fitted on annual incidence rates of influenza infection by age. We found that natural influenza infection reduced the risk of being re-infected by 15.4% (95% confidence interval 7.1-23.0). Various scenarios of repeated influenza vaccination were then simulated and compared with a reference scenario where vaccination is given from age 65 years onwards. We show that repeated vaccination at a young age substantially increases the risk of influenza in older age, by a factor ranging between 1.2 (vaccination after 50 years) to 2.4 (vaccination from birth). These findings have important implications for influenza vaccination policies.

Adolescent↗

PubMed2006

A case-control study of risk factors for hepatitis C infection in patients with unexplained routes of infection.

Twenty to 40% of hepatitis C virus (HCV)-infected patients do not have a recognized parenteral risk factor, suggesting that still-unidentified modes of transmission exist. In order to investigate potential routes of HCV transmission for patients with no recognized parenteral risk factor, we conducted a multicentre case-control study. A total of 450 HCV-seropositive patients with no history of transfusion or intravenous drug use and 757 controls were recruited from the general population and matched for sex, age, geographical residence and number of chronic diseases. All subjects answered an interviewer-administered questionnaire on potential risk factors for HCV. Eighty per cent of cases had chronic hepatitis or cirrhosis. Respective percentages of genotypes 1, 2, 3, 4 and 5 were 65, 14, 11, 5 and 4. Among the 66 items considered, multivariate analysis identified 15 independent risk factors for HCV infection: nosocomial [admission to medical (odds ratio, OR = 2.1) or surgical ward (OR = 1.7), digestive endoscopy (OR = 1.9), abortion (OR = 1.7)], outpatient treatments [cutaneous ulcer and wound care (OR = 10.1), diathermy (OR = 3.0), gamma globulin (OR = 1.7), intravenous (OR = 1.7) or intramuscular (OR = 1.4) injections, varicose vein sclerotherapy (OR = 1.6), acupuncture (OR = 1.5)] and lifestyle-associated [intranasal cocaine use (OR = 4.5), practice of contact sports (OR = 2.3), beauty treatments (OR = 2.0), professional pedicure/manicure (OR = 1.7)]. These factors could explain 73% of community-acquired hepatitis C. In conclusion, for patients with unexplained routes of HCV infection, our data incriminate previously unidentified risk factors (abortions, some dermatological procedures, outpatient injections, contact sports, beauty treatments, professional pedicure/manicure) and confirm those already recognized (hospitalization, digestive endoscopy, acupuncture and intranasal cocaine use).

Adult↗

PubMed2006

Comparison of serum hepatitis C virus (HCV) RNA and core antigen levels in patients coinfected with human immunodeficiency virus and HCV and treated with interferon plus ribavirin.

Trak-C (Ortho-Clinical Diagnostics) is an enzyme-linked immunosorbent assay-based method capable of quantifying hepatitis C virus (HCV) core antigen (CA) in serum and could be an alternative to molecular detection and quantification of HCV RNA. We have evaluated the Trak-C assay in comparison with an HCV RNA quantitative assay (Versant HCV v3.0; Bayer Diagnostics) in the follow-up of 348 treated, human immunodeficiency virus (HIV)/HCV-coinfected patients included in the ANRS HC02 RIBAVIC trial. ANRS HC02 RIBAVIC is a therapeutic, multicenter, randomized protocol comparing the efficacy of alpha interferon 2b (IFN-alpha2b) (3 million units three times a week)-ribavirin (800 mg/day) to that of pegylated IFN-alpha2b (1.5 mug/kg of body weight/week)-ribavirin (800 mg/day) during 48 weeks of treatment of HIV/HCV-coinfected patients naïve to HCV treatment. Patients were assessed for virological analysis at day 0 and weeks 4, 12, 24, 48, and 72. Correlation of HCV RNA and HCV CA at the initiation of treatment was excellent (r = 0.92). HCV RNA and CA kinetics were similar during follow-up of HCV treatment from day 0 to week 72 whatever the group of response and genotype. The positive and negative predictive values of response to the treatment at week 4 were 59 and 94%, respectively, for HCV RNA load reduction of >2 log and 54 and 94%, respectively, for HCV CA below the threshold value (4.18 log(10) pg/ml . 10(4)). Trak-C, a new assay able to quantify CA in HIV/HCV-coinfected patients, correlates well with quantitative HCV RNA assays and is cheaper and easier to perform than molecular technology. HCV CA could be a valuable alternative test for therapeutic follow-up of coinfected patients treated with IFN plus ribavirin in developing countries.

Antiviral Agents↗

PubMed2005

Detailed analysis of the genetic evolution of influenza virus during the course of an epidemic.

The genetic variability of influenza virus is usually studied with sequences selected over numerous years and countries, and rarely within a single season. Here we examined the viral evolution and the correlation between genetic and clinical features during an epidemic. From a French prospective household-based study in 1999-2000, 99 infected patients were randomly selected. The HA1 genomic domain was sequenced. Phylogenetic analysis showed the existence of two groups of A/H3N2 viruses. We found no distinct pattern of genomic evolution within either group according to time. A spatial correlation with the nucleotide distances was shown. The average nucleotide diversity was 3.4x10-3 nucleotides per site, and did not differ between the groups. A lower number of segregating sites was observed in patients who experienced influenza-like symptoms during the previous epidemic. These results suggest that the influenza virus undergoes regular HA1 nucleotide changes, but without clonal expansion of mutant strains within a single epidemic.

Adult↗

PubMed2005

[Neuraminidase inhibitors in the general practice management of influenza: who prescribe them, when and with which results?].

OBJECTIVE: To describe in real-life conditions the flu therapeutic management, motivations to prescribe or not NAI (General Practitioners' (GPs) characteristics, decisional factors) and treated patients' course. DESIGN: A prospective, longitudinal, pharmacoepidemiological study involved 305 GPs in France during 2002-2003 winter epidemic peak. All patients>or=1 year old, with a clinical diagnostic of flu were included. RESULTS: One hundred and eighty-five GPs (150 NAI prescribing and 30 non-prescribing physicians) have included at least 1 patient. Prescribing physicians were the best informed on flu and NAI. 660 patients were analysed (250 NAI+ and 410 NAI-). 66% of NAI+ and 40% of NAI- attended to a consultation within 24 h (P<0.001). 31% of NAI+ and 20% of NAI- had a visit at home (P=0.002). Among the patients without complication at inclusion (N=585), 3% of NAI+ received an antibiotherapy vs 13% of NAI- (P<0.001). 43% of the patients had a sick leave, shorter for the NAI+ than NAI- (respectively, 3.7+/-1.7 vs 4.2+/-1.7 days, p=0.017). NAI was taken within 3 hours (median) after prescription by the 78% of the patients who returned their diary cards. The NAI+ patients had a faster improvement of symptoms than NAI- (within 24 h, respectively: 18 vs 5%, P<0.001) and they returned faster to routine activities (within 48 h, respectively: 27 vs 11%, P<0.001). CONCLUSIONS: This study evidenced the good use of NAI by the physicians. It confirms their therapeutic efficacy in real-life conditions and suggests their prescription allows decreasing antibiotic co-prescriptions and sick leaves duration, profits to consider in NAI benefit/risk ratio.

Anti-Bacterial Agents↗

PubMed2005

HIV and hepatitis C virus co-infection.

Explore the source record for details and available documents.

Antiviral Agents↗

PubMed2005

Management of chronic hepatitis C in French departments of internal medicine and infectious diseases.

This prospective, multicentre study was conducted during 2-30 April 2001 in the internal medicine/infectious diseases services in France and included data from 1858 hepatitis C virus (HCV)-infected patients, half of whom were HIV co-infected. The aims were to outline the type of pre-therapeutic evaluation of HCV infection performed (HCV RNA, genotype, liver biopsy); determine the proportion and characteristics of patients receiving antiviral treatment; and determine if any changes in these parameters had occurred between 1995 and 2001. Patients whom had a complete pre-therapeutic evaluation (39%, 709/1834) and received antiviral treatment (38%, 690/1830) were more likely to have abnormal liver biochemistry, cirrhosis and cryoglobulinaemia (P < 0.001). Injecting drug users and HIV-co-infected patients were less likely to have a complete pre-therapeutic evaluation or receive antiviral treatment (P < 0.001). A complete pre-therapeutic evaluation was more often performed in 2001 than in 1995 (39% vs. 6%, P < 0.001), including qualitative HCV RNA testing (91% vs. 68%, P < 0.001), genotyping (59% vs. 7%, P < 0.001) and a liver biopsy (60% vs. 29%, P < 0.001). The frequency of anti-HCV treatment approximately doubled between 1995 and 2001 (20% vs. 38%, P < 0001). Although adherence to consensus recommendations regarding pre-therapeutic evaluation is not ideal, a substantial improvement has occurred since 1995. Nevertheless, means of increasing the availability of antiviral therapies, particularly for patients with HIV co-infection or injecting drug use, require further study.

Adult↗

PubMed2004

A Bayesian MCMC approach to study transmission of influenza: application to household longitudinal data.

We propose a transmission model to estimate the main characteristics of influenza transmission in households. The model details the risks of infection in the household and in the community at the individual scale. Heterogeneity among subjects is investigated considering both individual susceptibility and infectiousness. The model was applied to a data set consisting of the follow-up of influenza symptoms in 334 households during 15 days after an index case visited a general practitioner with virologically confirmed influenza. Estimating the parameters of the transmission model was challenging because a large part of the infectious process was not observed: only the dates when new cases were detected were observed. For each case, the data were augmented with the unobserved dates of the start and the end of the infectious period. The transmission model was included in a 3-levels hierarchical structure: (i) the observation level ensured that the augmented data were consistent with the observed data, (ii) the transmission level described the underlying epidemic process, (iii) the prior level specified the distribution of the parameters. From a Bayesian perspective, the joint posterior distribution of model parameters and augmented data was explored by Markov chain Monte Carlo (MCMC) sampling. The mean duration of influenza infectious period was estimated at 3.8 days (95 per cent credible interval, 95 per cent CI [3.1,4.6]) with a standard deviation of 2.0 days (95 per cent CI [1.1,2.8]). The instantaneous risk of influenza transmission between an infective and a susceptible within a household was found to decrease with the size of the household, and established at 0.32 person day(-1) (95 per cent CI [0.26,0.39]); the instantaneous risk of infection from the community was 0.0056 day(-1) (95 per cent CI [0.0029,0.0087]). Focusing on the differences in transmission between children (less than 15 years old) and adults, we estimated that the former were more likely to transmit than adults (posterior probability larger than 99 per cent), but that the mean duration of the infectious period was similar in children (3.6 days, 95 per cent CI [2.3,5.2]) and adults (3.9 days, 95 per cent CI [3.2,4.9]). The posterior probability that children had a larger community risk was 76 per cent and the posterior probability that they were more susceptible than adults was 79 per cent.

Adolescent↗

PubMed2004

[Quantification of longitudinal myocardial velocities by Doppler tissue imaging during dobutamine echocardiography].

Doppler tissue imaging has been suggested to be a valuable method for the diagnosis of myocardial ischaemia during dobutamine echocardiography. The authors studied this mode of investigation in 49 consecutive patients (average age 60 +/- 12 years) referred for dobutamine stress echocardiography and who had undergone coronary angiography. The stress echo was carried out according to a standard protocol (5 to 40 m g/kg/min +/- atropine) with additional acquisition of 3 apical views (4, 2 and 3 chambers) with colour Doppler tissue imaging. Analysis of systolic and diastolic myocardial velocities was performed afterwards from digitised data. The different Doppler tissue parameters were measured in 12 left ventricular segments (excluding the apical segments) for each dosage of dobutamine: peak systolic velocity (S), Q-S duration, systolic velocity time integral (ITVS), peak early diastolic velocity (E), peak end diastolic velocity (A). These parameters were analysed throughout the stress for each segment without significant coronary stenosis to define normal values. ROC curves were constructed to determine threshold values of relative changes of velocity (between maximal dobutamine dosage and basal conditions) to improve detection of ischaemia in a segment with coronary stenosis (vessel diameter reduction > or = 70%). Similar diagnostic performances were observed with different systolic and diastolic parameters. The feasibility of measurement of diastolic velocities was, however, reduced (from 29% to 49%). The diagnostic accuracy of each parameter was the same for each vessel territory. A satisfactory concordance was observed between 2D echocardiography and Doppler tissue imaging for the detection of significant coronary stenosis in an analysis by vascular territory. The authors conclude that analysis of myocardial velocities during dobutamine stress echocardiography is feasible. It may be a useful complement for the detection of coronary stenosis during pharmacological stress echocardiography.

Coronary Stenosis↗

PubMed2002

Quality control of leucoreduced cellular blood components in France.

BACKGROUND AND OBJECTIVES: Since 1 April 1998, all cellular blood components in France have been leucoreduced. The current French standard is < 1 x 10(6) white blood cells (WBC) per unit with a 95% confidence that at least 97% of units will meet this standard. MATERIALS AND METHODS: Quality control (QC) data for leucoreduced cellular blood components were collected from the 41 French blood centres over a 5-month period. Conformance to the standard was determined using a non-parametric approach. RESULTS: More than 98% of the 15 286 red cell concentrates and of the 2895 platelet concentrates tested had < 1 x 10(6) WBC per unit. One filtration device gave unsatisfactory results and its use was discontinued. CONCLUSION: This QC survey shows an overall compliance with the standard. The data illustrate the practical value of identifying devices or centres with consistent QC problems.

Adult↗

PubMed2002

[D-Dimer determination combined with clinical probability for the diagnosis of leg venous thrombosis].

OBJECTIVE: To evaluate the results of combination of D-Dimer test and simple clinical model for the diagnosis of deep vein thrombosis (DVT). MATERIALS AND METHODS: Inclusion: clinical suspicion of DVT. Non inclusion criteria were Clinical model performed by the referring physician included probability varying from high to low. D-Dimer test was performed by five different rapid techniques. Standard of reference was Doppler ultrasonography (DU) performed by a senior radiologist. RESULTS: Eight hundred and fifty-four DU were performed on a 14 months time period, including 206 suspicion of pulmonary embolism, 109 postoperative time period, 120 non-included or excluded patients, 278 incomplete observations, 141 complete observations. DVT was present in 33 cases and absent in the other 108 cases (prevalence 23%). Sensitivity and negative predictive value of the five tests were between 82 and 97% and 90 et 97%. The most sensitive test had a specificity of 36% and a positive predictive value of 32%. Combination of clinical model and D-Dimer test did not improve the diagnostic accuracy. CONCLUSION: None of the test evaluated in the present study, even when combined with the clinical model results, did allow the exclusion of DVT.

Formycins↗

PubMed2001

Severe accidental hypothermia treated in an ICU: prognosis and outcome.

STUDY OBJECTIVES: To assess the characteristics and outcomes of patients admitted to an ICU for severe accidental hypothermia, and to identify risk factors for mortality. METHODS: All consecutive patients admitted to an ICU between January 1, 1979, and July 31, 1998, with a temperature of < or = 32 degrees C were retrospectively analyzed. Rewarming was always conducted passively with survival blankets and conventional covers. Prognostic factors were studied by means of univariate analysis (Mann-Whitney U and chi(2) tests) and multivariate analysis (logistic regression). RESULTS: Forty-seven patients were enrolled (mean +/- SD age, 61.7 +/- 16 years). Five patients had a cardiac arrest before ICU admission. Patient characteristics at ICU admission were as follows: temperature, 28.8 +/- 2.5 degrees C; systolic BP, 85 +/- 23 mm Hg; heart rate, 60 +/- 24 beats/min; Glasgow Coma Scale, 10.4 +/- 3.7; and simplified acute physiology score (SAPS) II, 50.9 +/- 27. Mechanical ventilation was necessary in 23 cases, and 22 patients in shock received vasoactive drugs. The mean length of stay in the ICU was 6.7 +/- 9 days. Eighteen patients (38%) died, but ventricular arrhythmia was never the cause. Univariate analysis identified several prognostic factors (p < 0.05): age (57 +/- 16 years vs 69 +/- 14 years), systolic arterial BP (93 +/- 20 mm Hg vs 71 +/- 21 mm Hg), blood bicarbonate level (23.5 +/- 5.2 mmol/L vs 16.6 +/- 6.2 mmol/L), SAPS II score (35.3 +/- 19.5 vs 72 +/- 21), mechanical ventilation (34% vs 81%), vasopressor agents (42% vs 82%), rewarming time (11.5 +/- 7.2 h vs 17.2 +/- 7 h), and discovery of the patient at home (2.3% vs 54.5%). The initial temperature did not influence vital outcome (28.9 +/- 2.6 degrees C vs 28.6 +/- 2.2 degrees C). Only the use of vasoactive drugs (odds ratio, 9; 95% confidence interval, 1.6 to 50.1) was identified as a prognostic factor in the multivariate analysis. CONCLUSION: Severe accidental hypothermia is a rare cause of ICU admission in an urban area. Its mortality remains high, but there is no overmortality according to the SAPS II-derived prediction of death. Shock, requiring treatment with vasoactive drugs, is an independent risk factor for mortality, while initial core temperature is not. It remains to be determined whether aggressive rather than passive rewarming procedures are better.

Adult↗

PubMed2001

[Does Doppler analysis of hepatic venous flow predict increased right atrial pressure and right ventricular dysfunction?].

The aim of this study was to test the hypothesis that Doppler study of hepatic venous flow, reflecting right atrial pressures and right ventricular dysfunction, allows prediction of increased right atrial pressure and right ventricular dysfunction in patients with right ventricular infarction. The authors studied 30 patients (27 men, mean age 54 +/- 12 years) in sinus rhythm with acute inferior myocardial infarction who underwent right heart catheterisation and Doppler echocardiography including recording of regurgitant and hepatic vein flow within 48 hours of hospital admission. Hepatic venous flow was used to measure peak velocity and velocity time integrals (VTI) of the systolic (S), diastolic (D) and atrial (a) contraction waves. The fraction of systolic filling was calculated: VTI S/VTI S + VTI D. The pressure half-time of pulmonary regurgitant flow (PHT IP) was also measured. Using haemodynamic criteria (non-compliant right atrial pressure wave form or right ventricular end diastolic pressure/pulmonary capillary pressure > or = 0.8), patients were divided into two groups: Group 1: right ventricular infarction (VD+, N = 22). Group 2: no right ventricular infarction (VD-, N = 8). No correlation was observed between Doppler parameters of hepatic venous flow and haemodynamic data, in particular right atrial pressure and pressure wave form. Moreover, no statistically significant difference was observed between the two groups with respect to the Doppler parameters derived from hepatic venous flow. On the other hand, the results confirmed good diagnostic performance of Doppler analysis of pulmonary regurgitant flow: sensitivity 80%, specificity 83%, positive predictive value 94%, negative predictive value 55%. The authors conclude that, in patients with acute inferior wall infarction, Doppler analysis of hepatic venous flow does not allow assessment of right atrial pressure or of ischaemic right ventricular dysfunction.

Adult↗

PubMed2000

[Comparing two groups of patients].

In medical research, comparing two groups of patients occurs frequently. The basic principles of comparison and the usual statistical tests--according to the types of variables and the choices of sampling methods--are presented. Elements needed for the computation of the size of a comparative study are given.

Humans↗

PubMed2000

The effect of ursodeoxycholic acid therapy on liver fibrosis progression in primary biliary cirrhosis.

Ursodeoxycholic acid (UDCA) is the only approved treatment for primary biliary cirrhosis (PBC). However, the benefit from UDCA therapy on the progression of PBC from its early stage towards extensive fibrosis and cirrhosis has not been clearly shown. The aim of this study was to assess the effect of UDCA therapy on liver fibrosis progression in PBC. A Markov model was used to analyze the progression rates between early and late histologic stages in 103 patients with PBC enrolled in a randomized, double-blind, placebo-controlled trial of UDCA. Early stage was defined by the presence of portal and periportal lesions without extensive fibrosis, whereas late stage was defined by the presence of numerous septa, bridging fibrosis, or cirrhosis. A total of 162 pairs of liver biopsy specimens were studied. The model accurately described the observed data. UDCA therapy was associated with a 5-fold lower progression rate from early stage disease to extensive fibrosis or cirrhosis (7% per year under UDCA vs. 34% per year under placebo, P <.002), but was not associated with a significant difference in regression rates (3% per year under both UDCA and placebo). At 4 years, the probability of UDCA-treated patients to remain in early stage disease is 76% (95% confidence interval: 58%-88%), as compared with 29% (15%-52%) in placebo-treated patients. In conclusion, UDCA therapy significantly delays the progression of liver fibrosis in PBC. Markov modeling should prove useful in assessing the efficacy of future medical treatments in clinical trials involving histologic endpoints.

Disease Progression↗

PubMed2000

A scale of methodological quality for clinical studies of radiologic examinations.

PURPOSE: To develop and evaluate a scale for assessment of the methodological quality for clinical investigations of radiologic studies. MATERIALS AND METHODS: A scale was developed that included methodological standards compiled from established sources for assessing the methodological quality of study designs in clinical research and characteristics related to biases commonly observed in clinical radiologic research. The scale was composed of 15 standards and was tested with the results of 96 studies on imaging of liver hemangioma. Interrater reliability was measured between two observers by using percentage agreement and kappa statistics. Interrater reliability between two observers for a composite quality index that encompassed the 15 standards was measured with the intraclass correlation coefficient. RESULTS: Agreement between the two observers was almost perfect (kappa value, 0.8-1.0) for 11 standards and substantial (kappa value, 0.74-0.78) for four standards. Agreement between the observers with regard to the composite quality index also was high (intraclass correlation coefficient r, 0.91 [95% CI: 0.87, 0.94]). CONCLUSION: The scale appears to be reliable for the assessment of methodological quality of clinical investigations of radiologic studies.

Hemangioma↗

PubMed2000

Comparison of a new method for the direct and simultaneous assessment of LDL- and HDL-cholesterol with ultracentrifugation and established methods.

BACKGROUND: Automated electrophoresis combined with enzymatic cholesterol staining might improve routine assessment of LDL- and HDL-cholesterol (LDLC and HDLC), as an alternative to the Friedewald equation and precipitation. A new method (Hydrasys; SEBIA) that adapts the cholesterol esterase/cholesterol oxidase reaction within urea-free gels was evaluated. METHODS: Fresh sera from 725 subjects (512 dyslipidemics) were analyzed by electrophoresis, in parallel with sequential ultracentrifugation, beta-quantification, calculation, and precipitation. RESULTS: Electrophoresis was linear up to 4 g/L cholesterol, with a detection limit of 0.042 g/L cholesterol/band. Within-run, between-run, between-batch, and between-operator imprecision (CVs) were 1.6%, 2.0%, 1.5%, and 2.7% for LDLC, and 3.9%, 4.3%, 5.5%, and 4.9% for HDLC, and remained unchanged up to 6.3 g/L plasma triglycerides (TGs). Precision decreased with very low HDLC (<0.25 g/L). Serum storage for 3-7 days at +4 or -80 degrees C did not interfere significantly with the assay. Agreement with beta-quantification was stable for LDLC up to 5.07 g/L (r = 0.94), even at TG concentrations >4 g/L (r = 0.91). Bias (2.88% +/- 12%) and total error (7.84%) were unchanged at TG concentrations up to 18.5 g/L. Electrophoresis predicted National Cholesterol Education Program cut-points with <0.04 g/L error, exactly and appropriately classified 79% and 96% of the subjects, and divided by 2.4 (all subjects) and 5.8 (TGs >1.5 g/L) the percentage of subjects underestimated by calculation. One-half of the patients with TGs >4 g/L had LDLC >1.30 g/L. For HDLC, correlation was better with precipitation (r = 0.87) than ultracentrifugation (r = 0.76). Error (-0.10% +/- 26%) increased when HDLC decreased (<0.35 g/L). Direct assessment of the LDLC/HDLC ratio detected 45% more high-risk subjects than the calculation/precipitation combination. CONCLUSIONS: Electrophoresis provides reliable quantification of LDLC, improving precision, accuracy, and concordance over calculation, particularly with increasing plasma TGs. Implementation of methods to detect low cholesterol concentrations could extend the applications for HDLC assessment.

Adolescent↗

PubMed1999

Monitoring epidemiologic surveillance data using hidden Markov models.

The analysis of routinely collected surveillance data is an important challenge in public health practice. We present a method based on a hidden Markov model for monitoring such time series. The model characterizes the sequence of measurements by assuming that its probability density function depends on the state of an underlying Markov chain. The parameter vector includes distribution parameters and transition probabilities between the states. Maximum likelihood estimates are obtained with a modified EM algorithm. Extensions are provided to take into account trend and seasonality in the data. The method is demonstrated on two examples: the first seeks to characterize influenza-like illness incidence rates with a mixture of Gaussian distributions, and the other, poliomyelitis counts with mixture of Poisson distributions. The results justify a wider use of this method for analysing surveillance data.

Disease Outbreaks↗