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Nutrition improvement with multipurpose trees could be a means of increasing milk yield. The present study was conducted to evaluate the effect of Moringa oleifera supplementation on the productive and reproductive performance of goats. The Panicum maximum was replaced by Moringa oleifera at the level of 0, 25, 50, 75, and 100% of group T1, T2, T3, T4, and T5, respectively. Data recorded on conception rate, kids' birth weight; dry matter intake (DM), average daily gain, and milk yield; and kids' DM intake of West African Dwarf (WAD) goats. The highest value for conception rate (50%), DM intake (3.08%), average daily gain (44.30 g/day), and milk yield (0.5 kg/day) were observed in the does fed T4 diet, except for kids birth weight (1.70 kg) at T3. The does fed T5 diet had the least values. Kids from T4 diet had significantly (P=0.05) the highest DM intake (152.33 g/day). M. oleifera herbage supplementation at 25 % with 75 % P. maximum based diet improved reproductive and lactation characteristics of WAD goats. [ABSTRACT FROM AUTHOR]

This study assessed the effect of partial replacement of cement with plantain peel ash (PPA) and Polystrene (POL) on the compressive strength of concrete as a means of managing waste. Concrete specimens were prepared with a mix ratio of 1:2:4 (cement: sand: granite) water/cement ratio of 0.6, thereafter cement was partially replaced with PPA, POL and PPA/POL in increasing percentages of 5, 10, 15 and 20% by weight. Physical, chemical and microstructural analyses were also conducted on the aggregates and materials used. Workability of the concrete specimens was observed to improve upon addition of PPA and POL separately but not with blended PPA/POL while compressive strength decreased with addition of the three compounds. The observed results can be attributed to the lack of sufficient cementitious properties in the materials, and hence, the study discourages the use of these materials as they do not significantly improve concrete strength. [ABSTRACT FROM AUTHOR]

Background and Objective: The rise of academic cyberloafing — the non-academic use of internet connections during class — has emerged as a concern within the university context. While cyberloafing in the workplace has received ample attention, its counterpart in educational settings, particularly in Nigeria, remains less explored. This study aimed to explore and describe the experiences and perspectives of undergraduate students at a private Nigerian university regarding cyberloafing. Method: Using an adaption of the Cyberloafing in Educational Settings Scale, this study targeted a class of 15 final-year library and information science students. Data collected online underwent qualitative description and was presented verbatim. Results: Though students were unfamiliar with the term 'cyberloafing,' they acknowledged participating in such behaviors. The findings revealed habitual social media use during class hours, the employment of online tools for academic purposes, and a prevalent trend of gaming activities, often driven by internet addiction and boredom. Students also conveyed an understanding of the potential downsides and benefits of digital engagements during academic hours. Conclusion: The study urges university policymakers to implement measures promoting positive internet use and incorporate ethical cyber behavior awareness into curricula. It further recommends that parents and lecturers foster proper online usage and advocates for society-wide campaigns to raise awareness about ethical digital technology behavior.

The Covid-19 pandemic resulted in a global lockdown and the cessation of all academic activities on-site. Higher education in Nigeria was not exempt, as a paradigm shift was required for university officials to explore non-conventional teaching methods to prevent students from wasting time and to keep them intellectually engaged. During the pandemic, our research examines how a private institution in Ede, Osun State, Nigeria, utilised the social networking platform WhatsApp for Ph.D. student seminars. The study obtained data from ten doctoral students in the Department of Library and Information Science at Adeleke University via online interviews. The difficulties faced by the students and the benefits of utilising ICT were highlighted. Due to the constant insecurity and poor road network in Nig eria, as well as the risk of long-distance travel, especially for postgraduate students who are not always resident on campus, we recommend the continued use of E-learning platforms in Higher Education Institutions as a solution to reducing transportation costs.

The concentrations of eleven (11) polyaromatic hydrocarbons (PAHs) and total hydrocarbons (THC) were investigated in the water, sediment, Chrysichthys nigrodigitatus and Macrobrachium macrobrachion from Badagry Creek and Ologe Lagoon in Lagos, Nigeria using EPA and Gas Chromatography (GC) methods. All the samples(except water measured in mg/l) were measured in µg/g. PAHs were not significantly different(p>0.05)across the two stations and were within WHO recommended limit. The highest concentration of THC from Badagry Creek was recorded in M. macrobrachion (219.565±171.891 µg/g) and this value exceeded WHO recommended limit. Similarly, the highest THC (211.565±127.923 µg/g) recorded in M. macrobrachion at Ologe Lagoon was above WHO limit. The study has shown that the polyaromatic hydrocarbons were below the risk level, which indicated no risk status from the consumption of the fish species studied. However, C. nigrodigitatus and M. macrobrachion studied from these water bodies are highly contaminated with THC. Therefore, persistent monitoring and strict adherence to responsible waste discharge should be upheld by all industries near these waters in order to avoid deleterious effects on the biota as well as ensuring safety of the consumers. [ABSTRACT FROM AUTHOR]

Abstract After the successful roll out of MenAfriVac, Nigeria has experienced sequential meningitis outbreaks attributed to meningococcus serogroup C (NmC). Zamfara State in North-western Nigeria recently was at the epicentre of the largest NmC outbreak in the 21st Century with 7,140 suspected meningitis cases and 553 deaths reported between December 2016 and May 2017. The overall attack rate was 155 per 100,000 population and children 5–14 years accounted for 47% (3,369/7,140) of suspected cases. The case fatality rate (CFR) among children 5–9 years was 10%, double that reported among adults ≥ 30 years (5%). NmC and pneumococcus accounted for 94% (172/184) and 5% (9/184) of the laboratory-confirmed cases, respectively. The sequenced NmC belonged to the ST-10217 clonal complex (CC). All serotyped pneumococci were PCV10 serotypes. The emergence of NmC ST-10217 CC outbreaks threatens the public health gains made by MenAfriVac, which calls for an urgent strategic action against meningitis outbreaks.

In an effort to expand the knowledge base on the use of non conventional feedstuff in rabbit nutrition, the nutritional potential and the cost effectiveness of using cassava peels fermented with rumen filtrate (enhanced cassava peel) for 21 days was investigated using twenty four (24) growing crossbred rabbits of mixed sexes and with a mean body weight of 506.8 ± 6.0g (mean ± SD). The rabbits were divided into three (3) treatment groups of eight (8) rabbits each with each rabbit serving as a replicate in a completely randomized design experiment. The control group was fed with a diet containing maize as the energy source while the remaining two groups were fed with diets in which the maize was replaced with 50% and 100% enhanced cassava peel meals(ECPM) respectively. Final weight and daily weight gain were similar (P > 0.05) in rabbits fed maize-based control and those fed diet containing 50% enhanced cassava peel meal (ECPM). The weights of the rabbits on 100%ECPM were also similar (P>0.05) to the control although lower (P < 0.05) than 50% ECPM. Diet 3 (100% ECPM) had the least cost (204.44) per kilogramme weight gain while the control had the highest (301.97). All the relative organ weights, except the heart, were significantly (P<0.05) affected by the dietary treatments. It was concluded that fermenting sun dried cassava peels with rumen filtrate for 21 days had a high potential as a possible replacement for maize in rabbit diet. The use of this agricultural by-product can reduce the cost of rabbit production, increase the availability of cheaper animal protein for the populace, generate higher profit margins for the livestock farmer and reduce environmental pollution. [ABSTRACT FROM AUTHOR]

This study assesses stabilizing lateritic soil using Terrasil solution. Preliminary tests were carried out on six natural soil samples from three borrow pit locations-two soil samples from a particular borrow pit location, for the purpose of identification and classification. Soil samples 1 and 2 from borrow pit 3 were found to be poor, hence, needed stabilization. While the other four samples from borrow pits 1 and 2 were found to be good enough. Engineering property tests such as California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS) and Compaction tests were performed on both the natural soil samples and the stabilized lateritic soil samples which were stabilized by adding terrasil solution in percentages ranging from 0% to 16% at 2% interval. The results showed that the addition of terrasil solution enhanced the strength of the two soil samples from borrow pit 3. For soil sample 1, the unsoaked CBR values increased from 8.4% at 0% to optimum value of 30.3% at 12% terrasil solution, while for soil sample 2, the unsoaked CBR values increased from 6.2% to optimum value of 32.0% at 12% terrasil solution. It was therefore concluded that the terrasil solution serves as a cheap and effective stabilizing agent for poor soil.

National public health emergency operations centers (PHEOCs) serve as hubs for coordinating information and resources for effective emergency management. In the International Health Regulations (IHR 2005) Monitoring and Evaluation Framework, a simulation exercise is 1 of 4 components that can be used to test the functionality of a country's emergency response capabilities in a simulated situation. To test the functionality of PHEOCs in World Health Organization African Region member states, a regional functional exercise simulating an Ebola virus disease outbreak was conducted. The public health actions taken in response to the simulated outbreak were evaluated against the exercise objectives. Thematic analysis was conducted to summarize key strengths and areas for improvement. From December 6 to 7, 2022, more than 1,000 representatives from 36 of the 47 African Region member states participated in the exercise from their respective PHEOCs. Approximately 95% of the 461 participants polled agreed with the positive responses to the postexercise survey. More than half of the PHEOC participants were able to test their existing emergency preparedness and response plans and became familiar with the expected roles to be fulfilled during an event. Of the participants who responded to the survey, over 90% reported that the exercise helped them understand their roles during emergency management. The exercise met its objectives and provided an opportunity to test the functionality of PHEOCs using realistic scenarios, and it helped participants understand existing response systems and procedures. However, the exercise also revealed areas for improvement in terms of the timing and preparation of participants. We recommend conducting functional exercises at the regional and national levels at least once a year, early or midyear, to allow many stakeholders to take part in the exercise. Moreover, there is a need to train country-level evaluators and controllers in designing and conducting functional exercises.

Background: Suboptimal detection and response to recent outbreaks, including COVID-19 and mpox (formerly known as monkeypox), have shown that the world is insufficiently prepared for public health threats. Routine monitoring of detection and response performance of health emergency systems through timeliness metrics has been proposed to evaluate and improve outbreak preparedness and contain health threats early. We implemented 7-1-7 to measure the timeliness of detection (target of ≤7 days from emergence), notification (target of ≤1 day from detection), and completion of seven early response actions (target of ≤7 days from notification), and we identified bottlenecks to and enablers of system performance., Methods: In this retrospective, observational study, we conducted reviews of public health events in Brazil, Ethiopia, Liberia, Nigeria, and Uganda with staff from ministries of health and national public health institutes. For selected public health events occurring from Jan 1, 2018, to Dec 31, 2022, we calculated timeliness intervals for detection, notification, and early response actions, and synthesised identified bottlenecks and enablers. We mapped bottlenecks and enablers to Joint External Evaluation (second edition) indicators., Findings: Of 41 public health events assessed, 22 (54%) met a target of 7 days to detect (median 6 days [range 0-157]), 29 (71%) met a target of 1 day to notify (0 days [0-24]), and 20 (49%) met a target of 7 days to complete all early response actions (8 days [0-72]). 11 (27%) events met the complete 7-1-7 target, with variation among event types. 25 (61%) of 41 bottlenecks to and 27 (51%) of 53 enablers of detection were at the health facility level, with delays to notification (14 [44%] of 32 bottlenecks) and response (22 [39%] of 56 bottlenecks) most often at an intermediate public health (ie, municipal, district, county, state, or province) level. Rapid resource mobilisation for responses (six [9%] of 65 enablers) from the national level enabled faster responses., Interpretation: The 7-1-7 target is feasible to measure and to achieve, and assessment with this framework can identify areas for performance improvement and help prioritise national planning. Increased investments must be made at the health facility and intermediate public health levels for improved systems to detect, notify, and rapidly respond to emerging public health threats., Funding: Bill & Melinda Gates Foundation., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

COVID-19 mortality rate has not been formally assessed in Nigeria. Thus, we aimed to address this gap and identify associated mortality risk factors during the first and second waves in Nigeria. This was a retrospective analysis of national surveillance data from all 37 States in Nigeria between February 27, 2020, and April 3, 2021. The outcome variable was mortality amongst persons who tested positive for SARS-CoV-2 by Reverse-Transcriptase Polymerase Chain Reaction. Incidence rates of COVID-19 mortality was calculated by dividing the number of deaths by total person-time (in days) contributed by the entire study population and presented per 100,000 person-days with 95% Confidence Intervals (95% CI). Adjusted negative binomial regression was used to identify factors associated with COVID-19 mortality. Findings are presented as adjusted Incidence Rate Ratios (aIRR) with 95% CI. The first wave included 65,790 COVID-19 patients, of whom 994 (1∙51%) died; the second wave included 91,089 patients, of whom 513 (0∙56%) died. The incidence rate of COVID-19 mortality was higher in the first wave [54∙25 (95% CI: 50∙98-57∙73)] than in the second wave [19∙19 (17∙60-20∙93)]. Factors independently associated with increased risk of COVID-19 mortality in both waves were: age ≥45 years, male gender [first wave aIRR 1∙65 (1∙35-2∙02) and second wave 1∙52 (1∙11-2∙06)], being symptomatic [aIRR 3∙17 (2∙59-3∙89) and 3∙04 (2∙20-4∙21)], and being hospitalised [aIRR 4∙19 (3∙26-5∙39) and 7∙84 (4∙90-12∙54)]. Relative to South-West, residency in the South-South and North-West was associated with an increased risk of COVID-19 mortality in both waves. In conclusion, the rate of COVID-19 mortality in Nigeria was higher in the first wave than in the second wave, suggesting an improvement in public health response and clinical care in the second wave. However, this needs to be interpreted with caution given the inherent limitations of the country's surveillance system during the study., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Monkeypox (MPX) is a viral zoonosis with lesions like smallpox. Though rare in Nigeria, sporadic outbreaks have been reported in 17 states since September 2017. Unfortunately, the COVID-19 pandemic has further reduced surveillance and reporting of MPX disease. This study seeks to assess the effect of an enhanced surveillance approach to detect MPX cases and measure the cumulative incidence of MPX in priority states in Nigeria. We identified three priority states (Rivers, Delta and Bayelsa) and their Local Government Areas (LGAs) based on previous disease incidence. We also identified, trained, and incentivized community volunteers to conduct active case searches over three months (January to March 2021). We supported case investigation of suspected cases and followed up on cases in addition to routine active surveillance for MPX in health facilities and communities. Weekly and monthly follow-up was carried out during the same period. Out of the three states, 30 hotspots LGAs out of the 56 LGAs (54%) were engaged for enhanced surveillance. We trained three state supervisors, 30 LGA surveillance facilitators and 600 Community informants across the three priority states. Overall, twenty-five (25) suspected cases of MPX were identified. Out of these, three (12%) were confirmed as positive. Enhanced surveillance improved reporting of MPX diseases in hotspots LGAs across the priority states. Extension of this surveillance approach alongside tailored technical support is critical intra and post-pandemic., Competing Interests: Conflict of interest: The authors declare no potential conflict of interest., (©Copyright: the Author(s).)

Background: Infection prevention and control (IPC) activities play a large role in preventing the transmission of SARS-CoV-2 in healthcare settings. This study describes the state of IPC preparedness within health facilities in Nigeria during the early phase of coronavirus disease (COVID-19) pandemic., Methods: We carried out a cross sectional study of health facilities across Nigeria using a COVID-19 IPC checklist adapted from the U.S Centers for Disease Control and Prevention. The IPC aspects assessed were the existence of IPC committee and teams with terms of reference and workplans, IPC training, availability of personal protective equipment and having systems in place for screening, isolation and notification of COVID-19 patients. Existence of the assessed aspects was regarded as preparedness in that aspect., Results: In total, 461 health facilities comprising, 350 (75.9%) private and 111 (24.1%) public health facilities participated. Only 19 (4.1%) health facilities were COVID-19 treatment centres with 68% of these being public health facilities. Public health facilities were better prepared in the areas of IPC programme with 69.7% of them having an IPC focal point versus 32.3% of private facilities. More public facilities (59.6%) had an IPC workplan versus 26.8% of private facilities. Neither the public nor the private facilities were adequately prepared for triaging, screening, and notifying suspected cases, as well as having trained staff and equipment to implement triaging., Conclusions: The results highlight the need for government, organisations and policymakers to establish conducive IPC structures to reduce the risk of COVID-19 transmission in healthcare settings., Competing Interests: Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2022.)

Timely access to emergency funding has been identified as a bottleneck for outbreak response in Nigeria. In February 2019, a new revolving outbreak investigation fund (ROIF) was established by the Nigeria Centre for Disease Control (NCDC). We abstracted the date of NCDC notification, date of verification, and date of response for 25 events that occurred prior to establishing the fund (April 2017 to August 2019) and for 8 events that occurred after establishing the fund (February to October 2019). The median time to notification (1 day) and to verification (0 days) did not change after establishing the ROIF, but the median time to response significantly decreased, from 6 days to 2 days ( P  = .003). Response to disease outbreaks was accelerated by access to emergency funding with a clear approval process. We recommend that the ROIF should be financed by the national government through budget allocation. Finally, development partners can provide financial support for the existing fund and technical assistance for protocol development toward financial accountability and sustainability.

Background: With reports of surges in COVID-19 case numbers across over 50 countries, country-level epidemiological analysis is required to inform context-appropriate response strategies for containment and mitigation of the outbreak. We aimed to compare the epidemiological features of the first and second waves of COVID-19 in Nigeria., Methods: We conducted a retrospective analysis of the Surveillance Outbreak Response Management and Analysis System data of the first and second epidemiological waves, which were between 27 February and 24 October 2020, and 25 October 2020 to 3 April 2021, respectively. Descriptive statistical measures including frequencies and percentages, test positivity rate (TPR), cumulative incidence (CI) and case fatality rates (CFRs) were compared. A p value of <0.05 was considered statistically significant. All statistical analyses were carried out in STATA V.13., Results: There were 802 143 tests recorded during the study period (362 550 and 439 593 in the first and second waves, respectively). Of these, 66 121 (18.2%) and 91 644 (20.8%) tested positive in the first and second waves, respectively. There was a 21.3% increase in the number of tests conducted in the second wave with TPR increasing by 14.3%. CI during the first and second waves were 30.3/100 000 and 42.0/100 000 respectively. During the second wave, confirmed COVID-19 cases increased among females and people 30 years old or younger and decreased among urban residents and individuals with travel history within 14 days of sample collection (p value <0.001). Most confirmed cases were asymptomatic at diagnosis during both waves: 74.9% in the first wave; 79.7% in the second wave. CFR decreased during the second wave (0.7%) compared with the first wave (1.8%)., Conclusion: Nigeria experienced a larger but less severe second wave of COVID-19. Continued implementation of public health and social measures is needed to mitigate the resurgence of another wave., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Public Health Emergency Operations Centres (PHEOCs) provide a platform for multisectoral coordination and collaboration, to enhance the efficiency of outbreak response activities and enable the control of disease outbreaks. Over the last decade, PHEOCs have been introduced to address the gaps in outbreak response coordination. With its tropical climate, high population density and poor socioeconomic indicators, Nigeria experiences large outbreaks of infectious diseases annually. These outbreaks have led to mortality and negative economic impact as a result of large disparities in healthcare and poor coordination systems. Nigeria is a federal republic with a presidential system of government and a separation of powers among the three tiers of government which are the federal, state and local governments. There are 36 states in Nigeria, and as with other countries with a federal system of governance, each state in Nigeria has its budgets, priorities and constitutional authority for health sector interventions including the response to disease outbreaks. Following the establishment of a National PHEOC in 2017 to improve the coordination of public health emergencies, the Nigeria Centre for Disease Control began the establishment of State PHEOCs. Using a defined process, the establishment of State PHEOCs has led to improved coordination, coherence of thoughts among public health officials, government ownership, commitment and collaboration. This paper aims to share the experience and importance of establishing PHEOCs at national and subnational levels in Nigeria and the lessons learnt which can be used by other countries considering the use of PHEOCs in managing complex emergencies., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: This study aimed to develop and validate a symptom prediction tool for COVID-19 test positivity in Nigeria., Design: Predictive modelling study., Setting: All Nigeria States and the Federal Capital Territory., Participants: A cohort of 43 221 individuals within the national COVID-19 surveillance dataset from 27 February to 27 August 2020. Complete dataset was randomly split into two equal halves: derivation and validation datasets. Using the derivation dataset (n=21 477), backward multivariable logistic regression approach was used to identify symptoms positively associated with COVID-19 positivity (by real-time PCR) in children (≤17 years), adults (18-64 years) and elderly (≥65 years) patients separately., Outcome Measures: Weighted statistical and clinical scores based on beta regression coefficients and clinicians' judgements, respectively. Using the validation dataset (n=21 744), area under the receiver operating characteristic curve (AUROC) values were used to assess the predictive capacity of individual symptoms, unweighted score and the two weighted scores., Results: Overall, 27.6% of children (4415/15 988), 34.6% of adults (9154/26 441) and 40.0% of elderly (317/792) that had been tested were positive for COVID-19. Best individual symptom predictor of COVID-19 positivity was loss of smell in children (AUROC 0.56, 95% CI 0.55 to 0.56), either fever or cough in adults (AUROC 0.57, 95% CI 0.56 to 0.58) and difficulty in breathing in the elderly (AUROC 0.53, 95% CI 0.48 to 0.58) patients. In children, adults and the elderly patients, all scoring approaches showed similar predictive performance., Conclusions: The predictive capacity of various symptom scores for COVID-19 positivity was poor overall. However, the findings could serve as an advocacy tool for more investments in resources for capacity strengthening of molecular testing for COVID-19 in Nigeria., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: Despite the increasing disease burden, there is a dearth of context-specific evidence on the risk factors for COVID-19 positivity and subsequent death in Nigeria. Thus, the study objective was to identify context-specific factors associated with testing positive for COVID-19 and fatality in Nigeria., Design: Retrospective cohort study., Setting: COVID-19 surveillance and laboratory centres in 36 states and the Federal Capital Territory reporting data to the Nigeria Centre for Disease Control., Participants: Individuals who were investigated for SARS-CoV-2 using real-time PCR testing during the study period 27 February-8 June 2020., Methods: COVID-19 positivity and subsequent mortality. Multivariable logistic regression analyses were performed to identify factors independently associated with both outcome variables, and findings are presented as adjusted ORs (aORs) and 95% CIs., Results: A total of 36 496 patients were tested for COVID-19, with 10 517 confirmed cases. Of 3215 confirmed cases with available clinical outcomes, 295 died. Factors independently associated with COVID-19 positivity were older age (p value for trend<0.0001), male sex (aOR 1.11, 95% CI 1.04 to 1.18) and the following presenting symptoms: cough (aOR 1.23, 95% CI 1.13 to 1.32), fever (aOR 1.45, 95% CI 1.45 to 1.71), loss of smell (aOR 7.78, 95% CI 5.19 to 11.66) and loss of taste (aOR 2.50, 95% CI 1.60 to 3.90). An increased risk of mortality following COVID-19 was observed in those aged ≥51 years, patients in farming occupation (aOR 7.56, 95% CI 1.70 to 33.53) and those presenting with cough (aOR 2.06, 95% CI 1.41 to 3.01), breathing difficulties (aOR 5.68, 95% CI 3.77 to 8.58) and vomiting (aOR 2.54, 95% CI 1.33 to 4.84)., Conclusion: The significant risk factors associated with COVID-19 positivity and subsequent mortality in the Nigerian population are similar to those reported in studies from other countries and should guide clinical decisions for COVID-19 testing and specialist care referrals., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Competing Interests: Competing interests: The authors completed the ICMJE Unified Competing Interest form (available upon request from the corresponding author), and declare no conflicts of interest.