Identification of transmission chains and clusters associated with COVID-19 in Tunisia

BACKGROUND

The aim of this study was to characterize the transmission chains and clusters of COVID-19 infection in Tunisia.

METHODS

All cases were confirmed by Reverse Transcriptase Polymerase Chain Reaction of a nasopharyngeal specimen. Contact tracing is undertaken for all confirmed cases in order to identify close contacts that will be systematically screened and quarantined. Transmission chains were identified based on field investigation, contact tracing, results of screening tests and by assessing all probable mode of transmission and interactions.

RESULTS

As of May 18, 2020, 656 cases out of a total of 1043 confirmed cases of Coronavirus disease 2019 belong to 127 transmission chains identified during the epidemic (mean age 42.36 years, Standard deviation 19.56 and sex ratio 0.86). The virus transmission is the most concentrated in the governorate of Tunis (31.5%), Ariana (10.2%) and Ben Arous (10.2%). Virus transmission occurred 50 times (9.72% of secondary transmission events) between two different governorates. A maximum of seven generations of secondary infection was identified, whereas 62% of these secondary infections belong the first generation. A total of 11 "super spreader" cases were identified in this investigation. Four large clusters have been identified. The evolution of secondary cases highlighted two peaks: one in 2nd April and a second in 16 th April whereas imported cases caused local transmission of virus during the early phase of the epidemic.

CONCLUSION

Correct contact tracing and early active case finding is useful to identify transmission chains and source of infection in order to contain the widespread transmission in the community.

Characteristics and prognostic factors of COVID-19 among infected cases: a nationwide Tunisian analysis

Background

The outbreak of coronavirus disease (COVID-19) continues to constitute an international public health concern. Few data are available on the duration and prognostic factors of the disease. We aimed to study the recovery time among a Tunisian cohort of COVID-19 confirmed patients and identify the prognostic factors.

Methods

A retrospective, nationwide study was conducted from March 2 to May 8, 2020, recruiting all patients who were diagnosed with COVID-19, by RT-PCR methods, in Tunisia. Data were collected via phone call interview. Kaplan-Meir Methods and Cox proportional hazards regression models were, respectively, used to study the recovery time and estimate its prognostic factors.

Results

One thousand and thirty patients with COVID-19 (aged 43.2 ± 18.2 years, 526 female (51.1%)) were enrolled. Among them 141 (14.8%) were healthcare professionals. Out of 173 patients (17.8%) admitted to the hospital, 47 were admitted in an intensive care unit. Among 827 patients who didn’t require specialized care, 55.5% were self-isolated at home, while the rest were in specialized centers. Six hundred and two patients were symptomatic. A total of 634 (61.6%) patients have recovered and 45 (4.4%) patients died. The median duration of illness was estimated to be 31 days (95% CI: [29–32]). Older age (HR = 0.66, CI:[0.46–0.96], P = 0.031) and symptoms (HR = 0.61, CI:[0.43–0.81], P = 0.021) were independently associated with a delay in recovery time. Being a healthcare professional (HR = 1.52, CI: [1.10–2.08], P = 0.011) and patients in home isolation compared to isolation centers (HR = 2.99, CI: [1.85–4.83], P < 10¯³) were independently associated with faster recovery time.

Conclusion

The duration of illness was estimated to be 1 month. However, this long estimated duration of illness may not equate to infectiousness. A particular attention must to be paid to elderly and symptomatic patients with closer monitoring.

Estimating transmission dynamics and serial interval of the first wave of COVID-19 infections under different control measures: a statistical analysis in Tunisia from February 29 to May 5, 2020

BACKGROUND

Describing transmission dynamics of the outbreak and impact of intervention measures are critical to planning responses to future outbreaks and providing timely information to guide policy makers decision. We estimate serial interval (SI) and temporal reproduction number (Rt) of SARS-CoV-2 in Tunisia.

METHODS

We collected data of investigations and contact tracing between March 1, 2020 and May 5, 2020 as well as illness onset data during the period February 29-May 5, 2020 from National Observatory of New and Emerging Diseases of Tunisia. Maximum likelihood (ML) approach is used to estimate dynamics of Rt.

RESULTS

Four hundred ninety-one of infector-infectee pairs were involved, with 14.46% reported pre-symptomatic transmission. SI follows Gamma distribution with mean 5.30 days [95% Confidence Interval (CI) 4.66-5.95] and standard deviation 0.26 [95% CI 0.23-0.30]. Also, we estimated large changes in Rt in response to the combined lockdown interventions. The Rt moves from 3.18 [95% Credible Interval (CrI) 2.73-3.69] to 1.77 [95% CrI 1.49-2.08] with curfew prevention measure, and under the epidemic threshold (0.89 [95% CrI 0.84-0.94]) by national lockdown measure.

CONCLUSIONS

Overall, our findings highlight contribution of interventions to interrupt transmission of SARS-CoV-2 in Tunisia.

Increasing resolution of airborne pollen forecasting at a discrete sampled area in the southwest Mediterranean Basin

Daily fluctuations of the airborne pollen concentrations produce variations on symptomatology in allergic population. Such fluctuations are influenced by local vegetal coverage, flowering phenology, geography and climatology. Since 1991, airborne pollen of Malaga province (southern Spain) has been monitored in 7 different locations. Malaga station has been kept operational uninterruptedly throughout the studied period, while the rest of the stations only worked in periods of 2-4 years. Weekly, its pollen information is updated online to inform the population in order to prevent allergic diseases. Increasing the spatial resolution of pollen information would be very useful for allergic population living at unsampled locations. Due to the impossibility of keeping operational a high number of pollen stations covering the whole province of Malaga, the aim of this study is to create spatial models to extrapolate and forecast the pollen concentrations to Malaga province by using the concentrations registered at the capital as unique input. To do so, the relationships obtained between the airborne pollen concentrations detected at Malaga city and those detected at the other stations have been used to elaborate models for the main pollen types registered at the province. These models were spatially interpolated all over the province by using co-kriging techniques and the Compensated Thermicity Index as covariable. As result of this work, pollen distribution of the 8 most prevalent taxa has been depicted all over the whole Malaga province and an allergy alert system has been set up to extrapolate pollen information from Malaga to the whole province.

[Hypertension prevalence, awareness, treatment and control: results from a community based survey]

The study objective was to assess the prevalence, level of awareness of treatment, and control of hypertension in a general population. We conducted a cross-sectional survey on 1837 adults 40-69 years old. Hypertension and control level are defined according to the WHO/ISH recommendations. HBP is defined as SBP > or = 140 and or DBP > or = 90 mm Hg and the use of blood pressure-lowering medication. Hypertension is controlled by medication if SBP < 140 and DBP < 90 mm Hg. We conduct analysis by socio demographic variable, medical history and CHDs risk factors. 44.3% of adults was hypertensive. The prevalence of hypertension was higher among women (48.2% versus 38.7% on men) and it increases in both genders with age, body mass index. Only 41% of the hypertensive were aware of having hypertension, among them, 74.1% declare that they are treated but only 13.2% were controlled. The study highlights the problem of the hypertension in a developing country. It contributes to identify the huge iceberg of this CVDs risk factor. The national strategy must focus on the population life style and drugs management. The question is how much will be the cost of HBP and CVDs control for a country which has a limited resources.

[Population surveillance of coronary heart disease]

OBJECTIVE

A cross-sectional population survey was carried out in the Ariana region in 2000-01. The aim of this study is to report the prevalence of CHD as indicated by ECG Minnesota coding.

METHOD

A randomly selected sample included 1837 adults 40-70 years. Data on socio-economic status, demographic, medical history, health behaviour, clinical and biological investigations were recorded. Risk factors (hypertension, dyslipedemia, obesity, diabetes) are defined according to WHO criterias. Standard supine 12 lead ECGs were recorded. All ECGs are red and classified according to the Minnesota codes criteria on CHD probable, CHD possible and on Major abnormalities and minor abnormalities.

RESULTS

CHD prevalence was higher on women. Major abnormalities are more common on women (20.6% vs 13%), while minor abnormalities prevalence was higher on men (15.5% vs 7.5%) (p<0.0001). The prevalence increased with age in both genders.

CONCLUSION

This study tested how feasible is the population approach on CVDs surveillance. It highlighted the burden of cardiovascular diseases and support that women are at risk as men are. The value of ECG findings must be integrated in the cardiovascular diseases surveillance to identify high risk population.

[Cardiovascular disease surveillance in Tunisia]

OBJECTIVE

To assess the Cardiovascular risk factors trend in community based surveys.

METHOD

Two population surveys were conducted in 1996-97 and 2000-01 in the Ariana region among 7608 adults 35-70 years aged. The surveys were based on: 1--a questionnary, 2--an anthropometrical and physical examination, 3--a biological investigation, and 4--an ECG registration for the second cohort.

RESULTS

Relative to the first survey, the prevalence of hypertension, diabetes, hypercholesterolemia didn't change significantly while borderline cholesterol increased on both genders, tobacco smoking decreased and ex-smokers increased on men. In both genders, hypertension and diabetes prevalence is low before 50 years but it increased after this age. Risk factors association is common: about 35% have more than two risk factors. This association is more common on women and diabetes-hypertension is the most frequent.

CONCLUSION

These two surveys integrated in a global surveillance program has contributed to assess the CVDs burden and to identify priorities and intervention relevant to epidemiological region context.

[Management of arterial hypertension: results of a Tunisian general practitioner survey]

The control of arterial hypertension (HT) is an endlessly hoped objective but usually not reached. Several factors are determinants. The physician role is crucial in the HT prevention. In order to evaluate knowledge, attitudes and behaviours of Tunisian physicians in HT management, we conducted a cross sectional study in 2002 using a self administered questionnaire addressed to physicians working in private and public sectors. 380 generalists participated to this study. 95.5% of them confirmed that HT constitutes a public health problem. 81.1% saw at least 4 patients with HT a week. 95% insisted on the importance of the primary prevention. 90% took care themselves patients. 71.5% confirmed the importance of a training and an entrainement for the measure of the blood pressure (BP). 3.7% made diagnosis after a single visit and 10.9% confirmed it only from described symptoms. 20.4% of the generalists chose the old classification as objective level of BP. Thiazidic Diuretics and beta blockers were most prescribed medicines in first intention. 9.4% stopped the treatment after stabilization of blood pressure. 60% of generalists had inadequate behaviour facing a not stabilized BP. Non observance of treatment by patients was indicated by 31% of the generalists, cost and break of the medicines' stock and disappearance of symptoms were the main causes advanced by the generalists. This study shows the existence of gaps in generalists' practical behaviour treating this disease. Measures aiming the medical practice improvement turn out necessary in particular the sensitization of the generalists by an adequate university training and a continuous medical training, and a regular evaluation of the national program of hypertension prevention and management.

[The first Tunisian cardiovascular diseases register: processes and results]

BACKGROUND

In Tunisia, cardiovascular diseases are the leading causes of death (30%) and a few studies conducted in the population have demonstrated that the level of their risk factors is increasing. For policy makers, the health system impact of these diseases is currently a crucial issue. The National Public Health Institute has identified the implementation of a morbidity register as a priority.

METHODS

A CVD morbidity register is implemented since 2001, in 3 different geographical populations having contrasted levels of health status (Tunis, Ariana and Ben Arous). The 3 regions are covering about 2 millions inhabitants which is the fifth of the overall Tunisian population. All coronary heart events occurring among adults 25 years old and above in the 3 populations are recorded. The diagnosis of events, case fatality and classification are defined according to MONICA criteria. The data are recorded from public and private hospitals, death certificates and autopsies.

RESULTS

During the year 2001, the total number of myocardial infarction events was estimated at 942: in men, the age-standardized rates were 163.8/100000 in Tunis population vs. 161.9 in Ariana and 170.5 in Ben Arous. In women, the rates were respectively 43.4, 61.1 and 44.6. Medical causes of death registration was the most crucial problem in spite of the implementation of the death certificate designed according to WHO model. Specific surveys for clinical assessment and surveillance of risk factors were conducted in the register populations.

CONCLUSION

It is the first time that data on coronary heart disease incidence and fatality are available in Tunisia through this experience which highlights the practical difficulties experienced in registering and coding coronary events in a developing country. The data source quality should be improved and the register should be integrated in the local health system.