Introduction
Drawing parallels with the post-acute viral syndromes seen in survivors of other coronavirus outbreaks, there’s a growing body of evidence pointing to prolonged and persistent symptoms following the acute stage of COVID-19 (Nalbandian et al., Reference Nalbandian, Sehgal, Gupta, Madhavan, McGroder, Stevens, Cook, Nordvig, Shalev and Sehrawat2021). These constellation of symptoms after COVID-19 are termed ‘long COVID’ or ‘post-COVID syndrome (PCS)’ (Phillips and Williams, Reference Phillips and Williams2021). According to the Centers of Disease Control and Prevention (CDC), PCS is a collection of symptoms patients can experience for a month or more after getting infected with COVID-19 (CDC, 2019; Phillips and Williams, Reference Phillips and Williams2021). Long-term effects of PCS include abnormal clinical parameters that prevail beyond two weeks of disease onset and do not return to normal baseline (Lopez-Leon et al., Reference Lopez-Leon, Wegman-Ostrosky, Perelman, Sepulveda, Rebolledo, Cuapio and Villapol2021). PCS can affect many organ systems and include persistent or fluctuating headache, dry cough, palpitations, malaise, and fatigue as well as mental health problems such as poor memory, sleeping difficulties, mood changes, and thinking and concentration difficulties, sometimes termed as ‘brain fog’ (Davis et al., Reference Davis, Assaf, McCorkell, Wei, Low, Re’em, Redfield, Austin and Akrami2021). These symptoms tend to relapse or worsen with physical or mental exertion, thus having a significant effect on patient productivity (Davis et al., Reference Davis, Assaf, McCorkell, Wei, Low, Re’em, Redfield, Austin and Akrami2021).
The lingering symptoms of COVID-19 were found to occur in hospitalized patients for up to six months after discharge and in home-isolated patients who had mild symptoms (Huang et al., Reference Huang, Huang, Wang, Li, Ren, Gu, Kang, Guo, Liu and Zhou2021). COVID-19-infected patients who needed hospitalization, and older adults with chronic conditions and psychological or psychiatric comorbidities were more likely to develop PCS (Daugherty et al., Reference Daugherty, Guo, Heath, Dasmariñas, Jubilo, Samranvedhya, Lipsitch and Cohen2021). A previous study found that 32% of patients who were hospitalized for COVID-19 infection experienced at least one symptom, while 55% of patients experienced at least three symptoms post recovery (Carfì et al., Reference Carfì, Bernabei and Landi2020). The presence of some clinical features during the COVID-19 infection such as diarrhoea, anosmia and shortness of breath increased the risk of developing persistent symptoms (Augustin et al., Reference Augustin, Schommers, Stecher, Dewald, Gieselmann, Gruell, Horn, Vanshylla, Di Cristanziano and Osebold2021).
Limited research has been conducted on the prevalence of PCS and associated risk factors among HCWs. This study aimed to assess the prevalence of PCS and identify associated risk factors among HCWs in a large tertiary care hospital, with the objective of deriving valuable insights and lessons for future pandemics and post-viral syndromes.
Methods
Study design and participants
A cross-sectional study was conducted using an online self-administered survey at a large tertiary medical centre in Beirut. HCWs including medical students, residents/fellows, physicians, and nurses working at the tertiary medical centre who had previously tested positive for COVID-19 were included in this study. HCWs with no previous history of COVID-19 infection were excluded.
Data collection
The mailing list of medical students, residents/fellows, physicians, and nurses working at the tertiary medical centre were obtained from the Faculty of Medicine and The School of Nursing administrations. All prospective participants were sent an online survey that contains a description of the study and a link to the web survey. By clicking on the online survey link, the participant indicates that he/she consents to participate in the study and is directed to the online survey. Participants were asked if they have been infected with COVID-19. Participants who answered ‘No’ were disqualified from continuing the survey. The survey was administered using a secure institutional platform. The survey was anonymous and did not collect personal identifying information. It took around 10 minutes to be completed. If a participant refuses to participate, he/she has the option to unsubscribe from the mailing list or exit the survey without penalty. Four reminder email messages were sent at one-week intervals. The survey answers were stored in a password-protected account.
Instruments and measurements
The survey consisted of four sections: (A) socio-demographics, behavioural factors, and comorbidity; (B) Work-related questions; (C) Assessment of PCS; (D) Assessment of anxiety, depression, burnout, and psychological well-being.
Section A: socio-demographics, behavioural factors, and comorbidity
Socio-demographic characteristics of participants were collected including age, gender, marital status, income sufficiency, body mass index, smoking status, alcohol consumption, vaccination status, history of COVID-19 infection, status of COVID-19 infection before or after vaccination, severity of COVID-19 infection and need for hospitalization or intensive care unit stay. The number of chronic prescriptions were collected as suggestive of comorbidity and as a surrogate for the ‘intensity’ of treatment necessary to adequately control chronic medical conditions (Stawicki et al., Reference Stawicki, Kalra, Jones, Justiniano, Papadimos, Galwankar, Pappada, Feeney and Evans2015).
Section B: work-related questions
Work-related questions collected the following variables: current occupation, years of practice, and involvement in the care of COVID-19 patients.
Section C: assessment of post-COVID-19 syndrome (PCS)
A questionnaire that measures PCS was adapted from Kayaaslan et al. (Reference Kayaaslan, Eser, Kalem, Kaya, Kaplan, Kacar, Hasanoglu, Coskun and Guner2021). It screened for symptoms such as fatigue, muscle pain, joint pain, shortness of breath, headache, depression, anxiety, insomnia, and others. The questionnaire was neither tested nor validated because PCS is a new entity. It included questions about the duration of symptoms, seeking medical care for PCS, lost workdays, and loss of workplace productivity. PCS or long-COVID was defined as COVID-19-associated symptoms extending for four weeks or more from the first infection (CDC, 2019).
Section D: assessment of anxiety, depression, burnout and psychological well-being
The 5-item World Health Organization Well-Being Index (WHO-5) is a short, self-administered questionnaire covering five positively worded items, related to positive mood (good spirits, relaxation), vitality (being active and waking up fresh and rested), and general interests (being interested in things). Each of the five items in the WHO-5 is rated on a 6-point Likert scale from zero (not present) to five (constantly present). The raw score ranges from zero to 25, and the author suggests the use of a percentage final score (0–100%), transforming the scale by simply multiplying the result by four. A cutoff < 13 (or < 50%) indicates poor psychological well-being (Bech, Reference Bech2004). The scale has adequate validity both as a measure of psychological well-being and a screening tool for depression, and as an outcome measure in clinical trials and has been applied successfully across a wide range of study fields (Topp et al., Reference Topp, Østergaard, Søndergaard and Bech2015).
The Patient Health Questionnaire-4 (PHQ-4) was used to screen for depression and anxiety. PHQ-4 is a 4-item inventory rated on a 4-point Likert scale. Its items are drawn from the first two items of the Generalized Anxiety Disorder–7 scale (GAD–7) and the Patient Health Questionnaire-9 (PHQ-9) (Kroenke et al., Reference Kroenke, Spitzer, Williams and Löwe2009). The first two items (PHQ-2) were for depression screening and were worded as: ‘Over the last two weeks, how often have you been bothered by Feeling down, depressed, or hopeless?’ and ‘Over the last two weeks, how often have you been bothered by Little interest or pleasure in doing things?’. The next two items (GAD-2) were for anxiety screening and were worded as follows: ‘Over the last two weeks, how often have you been bothered by feeling nervous, anxious, or on edge?’ and ‘Over the last two weeks, how often have you been bothered by not being able to stop or control worrying?’. The response options were not at all (score = 0), several days (score = 1), more than half the days (score = 2), and nearly every day (score = 3). PHQ-2, GAD-2, and PHQ-4 scores were computed by adding scores on individual items. PHQ-4 scores determine ‘Severe’ (9–12), ‘Moderate’ (6–8), ‘Mild’ (3–5), and ‘Normal’ (0–2) risk of anxiety or depression. On each subscale, a score of three or higher is considered a risk for anxiety or depression. The instrument is valid and reliable in the general population. The internal consistency and reliability statistics of the PHQ-4, PHQ-2, and GAD2 were: α = 0.78, α = 0.75, and α = 0.82, respectively (Löwe et al., Reference Löwe, Wahl, Rose, Spitzer, Glaesmer, Wingenfeld, Schneider and Brähler2010).
Burnout was measured using the nine-item abbreviated Maslach Burnout Inventory (aMBI) using three subscales (Riley et al., Reference Riley, Mohr and Waddimba2018). The emotional exhaustion (EE) subscale describes feelings of being emotionally exhausted because of work and contains three items (items 3, 4, 7). The depersonalization (DP) subscale describes detached and impersonal treatment of patients and consists of three items (items 2, 5, 8). The personal accomplishment (PA) subscale contains three items (items 1, 6, 9) that describe beliefs of competence and successful achievement at work whereby reduced personal accomplishment describes a feeling of reduced competence and a lack of success/achievement in one’s work with people. There are seven possible answers for each item with a score ranging from zero (never) to six (every day). Each subscale was scored separately as follows: EE subscale score ≤ 6: low burnout, 7–10: moderate burnout, ≥11: high burnout; DP subscale score ≤ 3: low burnout, 4–6: moderate burnout, ≥7: high burnout; PA subscale score >15: low burnout; 13–14: moderate burnout; ≤12: high burnout. Overall burnout was determined by summing the scores for EE and DP (cut-off ≥ 75 percentiles). The aMBI measures were found to be highly correlated with the original 22-item Maslach Burnout Inventory – Human Services Survey for Medical Personnel (MBI-HSS MP) and a valid screening test for burnout among healthcare professionals (Riley et al., Reference Riley, Mohr and Waddimba2018)
Statistical analysis
Descriptive analysis was performed by calculating frequency and percentages for categorical variables and mean and standard deviation for continuous variables. An independent sample T-test was used to test differences between means, and Chi-squared test was used to determine the association between categorical independent variables and categorical dependent variables. Bivariate analysis was performed to identify potential risk factors associated with the outcome variable (PCS). To predict the outcome (PCS), a multivariable logistic regression model was created with PCS as the dependent variable, and included all the variables that had a p-value < 0.20 in the bivariate analysis, which are: income, direct COVID care, COVID severity, hospitalization, well-being score, PHQ2 score, and MBI emotional score. The adjusted odds ratios were reported. A p-value of < 0.05 was used as a significance cutoff for all tests. The data was analysed using IBM’s SPSS version 28.0.0.0.
Results
A total of 213 responses were collected for the study; 134 participants reported having had COVID-19 at least four weeks prior to taking the survey, while 71 participants either never had COVID-19 or had it less than four weeks before the survey and were excluded from the analysis. Out of the 134 participants who had COVID-19, 64 participants (47.7%) reported suffering from PCS compared to 70 (52.3%) participants who did not suffer from PCS.
When comparing income sufficiency between participants with PCS and those without, it was observed that 65.6% of participants with PCS considered their income to be sufficient, while a majority of 80.9% of participants without PCS considered their income sufficient. However, this difference showed a trend towards significance (p = 0.071). Other socio-demographic characteristics are presented in Supplementary Table 1.
Examining clinical characteristics, participants with PCS predominantly reported moderate symptoms (57.8%), a markedly higher proportion than those without PCS (36.8%), a difference that was statistically significant with a p-value of 0.019. Hospitalization was a less common occurrence among participants, with 6.3% of PCS participants and 1.4% of non-PCS participants requiring hospital stay with no statistical significance. Additional information on the clinical characteristics is provided in Supplementary Table 2.
The most common symptoms reported by PCS participants were fatigue (81.3%), shortness of breath (59.4%), memory issues (57.8%), and difficulty concentrating (53.1%). For a significant majority of these participants (70.3%), these symptoms persisted up to three months post-COVID. A smaller segment (15.6%) experienced symptoms up to six months, and a nearly equivalent proportion (14.1%) reported symptom duration exceeding six months. Predominantly, patients with PCS sought care for respiratory symptoms (68.8%), followed by those who sought neurological care (25%) (Table 1). A psychological evaluation of the participants indicated a tendency towards decreased overall well-being and heightened emotional exhaustion in the PCS group, although the data did not yield statistical significance (Table 2).
Reported post-COVID symptoms among participants with PCS
PCS, Post-COVID Syndrome.
† Lost workdays, consecutive or not, are the number of working days after the onset of illness that the employee was away from work or limited to restricted work activity because of illness.
‡ Workplace productivity is the efficiency with which tasks and goals are accomplished at your work.
Psychological assessment of the study participants
DP, Depersonalization; EE, Emotional Exhaustion; GAD, Generalized Anxiety Disorder; PHQ, Patient Health Questionnaire; PA, Personal Accomplishment; PCS, Post-COVID Syndrome.
Multivariable logistic regression analysis used to predict PCS showed significant correlations with two variables, as outlined in Table 3. Firstly, a direct involvement in the care of COVID-19 patients corresponded with increased odds of PCS, with an adjusted odds ratio (aOR) of 2.60 (95% confidence interval (CI) of [1.02, 6.90], p = 0.049). Secondly, greater severity of COVID-19 also increased the odds of PCS, with an aOR of 2.30 (95% CI of [1.12, 4.99], p = 0.024).
Multivariable logistic regression predicting PCS
DP, Depersonalization; EE, Emotional Exhaustion; GAD, Generalized Anxiety Disorder; PHQ, Patient Health Questionnaire; PA, Personal Accomplishment; PCS, Post-COVID Syndrome.
* Statistical significance is set at p < 0.05.
† Sufficient income.
‡ Mild COVID.
§ No risk of depression.
¶ Low/moderate emotional exhaustion score (<11).
Discussion
This study examined the prevalence of PCS and its associated risk factors among HCWs. PCS was noted among half of the study participants. Our findings are consistent with similar research. A study conducted in Jordan demonstrated a prevalence of 59.3% of PCS among HCWs (Hyassat et al., Reference Hyassat, El-Khateeb, Dahbour, Shunnaq, Naji, Ata, Abujbara, Khawaja, Batieha and Ajlouni2023) revealing a slightly higher prevalence compared to our findings. In a large-scale Indian study, an overall prevalence of PCS of 30.34% among 679 HCWs was reported (Singh et al., Reference Singh, Mohanti, Mohapatra, Deep, Harsha, Pathak, Patro and Burgula2022). In a study conducted in Quebec, approximately 46% of the COVID-19 patients who did not require hospitalization were affected with PCS. The prevalence increased dramatically among the hospitalized HCWs, reaching a proportion of 76% (Carazo et al., Reference Carazo, Skowronski, Laforce, Talbot, Falcone, Laliberté, Denis, Deshaies, Hegg-Deloye and De Serres2022). A significant majority (70.3%) of our study participants disclosed the persistence of PCS symptoms for a duration extending from four weeks to three months. In contrast, a minor proportion constituting 15.6% reported enduring PCS symptoms for a duration of three to six months. Meanwhile, 14.1% indicated the persistence of PCS symptoms for more than six months. Similarly, the study conducted in Quebec found that nearly half (46%) of non-hospitalized COVID-19 patients had PCS, with 39.9% of their sample experiencing symptoms persisting for 12 weeks or longer (Carazo et al., Reference Carazo, Skowronski, Laforce, Talbot, Falcone, Laliberté, Denis, Deshaies, Hegg-Deloye and De Serres2022). Other studies reported that one third of hospital staff who contracted COVID-19 had persistent symptoms 3–4 months post-infection (Gaber et al., Reference Gaber, Ashish and Unsworth2021; Tsampasian et al., Reference Tsampasian, Elghazaly, Chattopadhyay, Debski, Naing, Garg, Clark, Ntatsaki and Vassiliou2023) and one quarter of senior specialist doctors experienced prolonged periods of ill health, while the majority reported that COVID-19 affected their general well-being (Doherty et al., Reference Doherty, Colleran, Durcan, Irvine and Barrett2022). The discrepancies in these findings could be attributed to various factors such as different study designs, survey methodologies, and participant demographics.
Exploring PCS prevalence across age and gender, prior research indicated an increased risk of persistent post-COVID-19 symptoms in older patients and among females (Tsampasian et al., Reference Tsampasian, Elghazaly, Chattopadhyay, Debski, Naing, Garg, Clark, Ntatsaki and Vassiliou2023). However, some studies reported no correlation between baseline clinical characteristics and risk of PCS (Moreno-Pérez et al., Reference Moreno-Pérez, Merino, Leon-Ramirez, Andres, Ramos, Arenas-Jiménez, Asensio, Sanchez, Ruiz-Torregrosa and Galan2021; Uniyal et al., Reference Uniyal, Sethi, Sharma, Sayana, Jeet, Agarwal and Rawat2022), consistent with our findings.
The most frequently reported PCS symptoms in our study were fatigue, shortness of breath, and memory impairment, consistent with previous research (Domingo et al., Reference Domingo, Waddell, Cheung, Cooper, Belcourt, Zuckermann, Corrin, Ahmad, Boland and Laprise2021; Singh et al., Reference Singh, Mohanti, Mohapatra, Deep, Harsha, Pathak, Patro and Burgula2022). Our study identified a significant correlation between the severity of COVID-19 infection and risk of PCS, in line with other studies (Maglietta et al., Reference Maglietta, Diodati, Puntoni, Lazzarelli, Marcomini, Patrizi and Caminiti2022; Singh et al., Reference Singh, Mohanti, Mohapatra, Deep, Harsha, Pathak, Patro and Burgula2022). Uniyal et al. reported an increased risk of persistent COVID-19 symptoms with disease severity, varying from 14% in mild cases to 39% in mild to moderate cases, with significance up to 12 weeks post-infection (Uniyal et al., Reference Uniyal, Sethi, Sharma, Sayana, Jeet, Agarwal and Rawat2022). Contrary to the findings reported by several studies (Carazo et al., Reference Carazo, Skowronski, Laforce, Talbot, Falcone, Laliberté, Denis, Deshaies, Hegg-Deloye and De Serres2022; Tsampasian et al., Reference Tsampasian, Elghazaly, Chattopadhyay, Debski, Naing, Garg, Clark, Ntatsaki and Vassiliou2023), we did not find a significant correlation between hospitalization and persistent PCS symptoms. This discrepancy could likely be attributed to the limited number of respondents from our sample who required hospitalization.
Existing literature confirms that frontline HCWs are at an increased risk of contracting COVID-19 (Nicola et al., Reference Nicola, Alsafi, Sohrabi, Kerwan, Al-Jabir, Iosifidis, Agha and Agha2020; Rajkumar, Reference Rajkumar2020) and developing PCS (Doherty et al., Reference Doherty, Colleran, Durcan, Irvine and Barrett2022; Gaber et al., Reference Gaber, Ashish and Unsworth2021). Those directly involved in patient care exhibited an increased propensity to develop PCS (Ladds et al., Reference Ladds, Rushforth, Wieringa, Taylor, Rayner, Husain and Greenhalgh2020). Inadequate personal protective equipment (PPE) has been implicated in heightened COVID-19 infection rates and a higher risk of PCS, particularly among frontliners in Italy, China, and America (Ing et al., Reference Ing, Xu, Salimi and Torun2020; Nguyen et al., Reference Nguyen, Drew, Graham, Joshi, Guo, Ma, Mehta, Warner, Sikavi and Lo2020). Adherence to strict infection control protocols within healthcare settings is essential in mitigating indirect virus transmission (Karia et al., Reference Karia, Gupta, Khandait, Yadav and Yadav2020). Measures such as minimizing physical contact, maintaining regular disinfection routines, and enforcing personal hygiene practices can substantially mitigate COVID-19 transmission risk among healthcare professionals.
Our results showed lower psychological wellbeing and higher emotional exhaustion within the PCS group, suggesting potential overlap of depression symptoms with PCS symptoms (Woodward et al., Reference Woodward, Bari, Vike, Lalvani, Stetsiv, Kim, Stefanopoulos, Maglaveras, Breiter and Katsaggelos2022). Other studies have also highlighted substantial rates of depression and anxiety among post-COVID patients, including HCWs (Renaud-Charest et al., Reference Renaud-Charest, Lui, Eskander, Ceban, Ho, Di Vincenzo, Rosenblat, Lee, Subramaniapillai and McIntyre2021). This decline in mental well-being may compromise immune function, increasing the susceptibility of HCWs to prolonged COVID-19 symptoms. Further research has suggested a possible link between HCW burnout, insufficient sleep, and the emergence of PCS (Shreffler et al., Reference Shreffler, Petrey and Huecker2020).
Impact on primary-care practice and policy for the next pandemic
The high proportion of HCWs in our cohort who developed PCS should be viewed as a sentinel warning for future outbreaks. The World Health Organization’s 2024 list of priority pathogens, from H5N1 to Nipah virus, shows that new agents with comparable post-viral sequelae are a near-certainty (Ukoaka et al., Reference Ukoaka, Okesanya, Daniel, Ahmed, Udam, Wagwula, Adigun, Udoh, Peter and Lawal2024). Planning for the next pandemic must therefore start in primary care, where most infections are diagnosed, most HCWs are employed, and most chronic sequelae eventually present.
Practice-level actions
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Early case-finding and longitudinal follow-up. Embedding brief PCS screeners in electronic medical-record templates and occupational-health encounters enables primary care teams to flag persistent symptoms rapidly and build registries that can be repurposed for future post-viral syndromes (WHO, 2024).
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Hybrid, resilient care pathways. COVID-era studies show that workflows combining face-to-face, telephone, and asynchronous digital reviews have maintained access and infection-control standards during surges; these hybrid models should now be written into routine primary care standard-operating procedures (Jeong et al., Reference Jeong, Crowell, Devon-Sand, Sakata, Sattler, Shah, Tsai and Lin2024).
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Multidisciplinary rehabilitation anchored in primary care. Delivery models emphasize that long-COVID clinics function best when physiotherapy, mental-health, and social-care input are co-located in community settings, reducing fragmentation and travel burden for both patients and staff (WHO, 2024).
Policy priorities
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Epidemic-ready primary health care. Frameworks such as the Epidemic-Ready Primary Health Care (ER-PHC) model integrate surveillance, infection-prevention, and routine care at the first point of contact; implementing ER-PHC elements (real-time reporting, just-in-time mobile training, facility-level emergency management) should become a core indicator of pandemic preparedness (Lives, Reference Lives2025).
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Workforce protection and well-being. Multi-country primary care surveys conducted after COVID-19 highlight burnout, absenteeism, and unclear PPE guidance as major vulnerabilities; pandemic plans must include funded PPE stockpiles, psychological-support hubs, and flexible duty rosters to keep primary care teams functional (Willems et al., Reference Willems, Vanden Bussche, Van Poel, Collins and Klemenc-Ketis2024).
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Sustainable financing and governance. The American College of Physicians and other bodies recommend ring-fenced budgets for primary care surge capacity, data-sharing mandates between public-health and primary care actors, and explicit inclusion of primary care representatives in national emergency-operations centres, recommendations that align with the draft WHO Pandemic Accord (Serchen et al., Reference Serchen, Cline, Mathew and Hilden2023; WHO, 2025). By adding evidence from an under-represented low- or middle-income country setting in the Middle East, our study strengthens the call for epidemic-ready, multidisciplinary primary care. Investing now in integrated surveillance, hybrid service models, and protected primary care workforces will not only mitigate the long-term burden of PCS but also build the first line of defence against whatever virus comes next.
Our study has some limitations, notably a relatively small sample size, potential recall bias due to self-reported data, and limited generalizability due to the single-site design. The cross-sectional nature of our study also restricted our ability to assess for causation between risk factors and PCS. Despite these limitations, our study investigated a broad range of PCS symptoms among different HCWs. While our results contribute valuable insights, further multicenter research with larger sample sizes is needed for a more comprehensive PCS profile. Given the ongoing evolution of COVID-19 and the introduction of new vaccines, future studies may be needed to redefine PCS in terms of symptoms and duration.
Conclusion
Our data confirms that PCS is not a fringe phenomenon but a persistent occupational hazard for frontline staff. Pandemic-preparedness policy must therefore extend beyond acute infection control to encompass (i) systematic, workplace-based screening for lingering symptoms, (ii) embedded mental-health services, and (iii) pragmatic workload safeguards such as capped shift length, roster flexibility and protected rest. Together, these measures can dampen the vicious cycle that links burnout, psychological distress and PCS.
Evidence from the Middle East remains scant; targeted epidemiological studies and intervention trials in this region are urgently needed to ensure that future guidelines are globally relevant. By investing now in primary-care–led surveillance and multidisciplinary PCS clinics, health systems will be better equipped to prevent, detect and manage long-tail sequelae whether from SARS-CoV-2 or from the next pandemic-grade virus.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S1463423625100510.
Data availability statement
The data that support the findings of this study are available on request from the corresponding author. The data is not publicly available due to privacy or ethical restrictions.
Author contributions
G.A. and L.A. designed and directed the study’s implementation. M.A.H. and G.D. performed the analysis. L.A., C.R., L.B., M.B., M.A., M.B.Z., N.T., N.B., and P.M. conducted the literature review and drafted the manuscript. All the authors read and approved the final manuscript.
Funding statement
The author(s) received no funding statement for the research of this article.
Competing interests
The author(s) declare none.
Ethical standards
This study was performed in accordance with the Code of Ethics of the World Medical Association (Helsinki Declaration of 1975, as revised in 2008). Approval was granted by the Institutional Review Board. Written informed consent was obtained from all participants.
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