Covid-19 et Sécurité Alimentaire en Afrique Subsaharienne : Implications et Mesures Proactives d’Atténuation des Risques de Malnutrition et de Famine

Ulbad Polycarpe TOUGAN, A. Théwis


The Covid-19 pandemic is a pandemic of an emerging infectious disease, 2019 coronavirus disease (Covid-19), caused by the coronavirus SARS-CoV-2. The countries of sub-Saharan Africa affected by the Covid-19 pandemic are increasingly confronted with the decline in raw materials and the fall in international trade. The essential protective measures recommended by the WHO (2020) to limit the spread of Coronavirus (Covid-19) characterized, among other things, by the suppression movement, quarantine, containment, closing of the borders are driving down household productivity. Disruptions in trade and in local food supply chains are already affecting the well-being of the households, food security and nutrition among importing countries. Food prices are going up, especially nutritious food. Hunger and malnutrition will increase as the livelihoods of the poor are affected. Not yet having a universally accepted treatment for Covid-19, it is necessary to have information on the nutritional resources which will make it possible to boost the immune system of vulnerable populations in the fight against COVID-19 in a context of food insecurity. This document outlines proactive measures to prevent the risks of malnutrition and starvation linked to the Covid-19 pandemic and describes the macronutrient and micronutrient composition of some foods. These measures relate to a healthy and balanced diet, the improvement of food hygiene, the intensification of agricultural and agro-food production, the improvement of culinary and gastronomic practices, the improvement of nutrition governance and food security in affected sub-Saharan African countries.


Sub-Saharan Africa, Covid-19, hygiene, malnutrition, food security

Full Text:



Dong E, Du H, Gardner L. 2020. An interactive web-based dashboard to track COVID-19 in real time. Lancet Infect Dis; published online Feb 19.

Heymann DL, Shindo N. 2020. « COVID-19: what is next for public health? », The Lancet, vol. 395, no 10224,‎ 22 février 2020, p. 542–545 (ISSN 0140-6736 et 1474-547X, PMID 32061313, DOI 10.1016/S0140-6736(20)30374-3.

Zhou P, Yang X-L, Wang X-G, Hu B. 2020. « Discovery of a novel coronavirus associated with the recent pneumonia outbreak in humans and its potential bat origin », bioRxiv, Microbiology,‎ 23 janvier 2020 (DOI 10.1101/2020.01.22.914952

World Health Organisation. 2020. Media briefing on COVID-19. March 13, 2020.

Maire B, Lioret S, Gartner A, Delpeuch F. 2002. Transition nutritionnelle et maladies chroniques liées à l’alimentation dans les pays en développement. Cahiers santé. 2002;12:45–55.

Holmes MD, Dalal S, Volmink J, Adebamowo CA, Njelekela M, Fawzi WW, Willett WC, Adami H-O. 2010. Non-communicable diseases in sub-Saharan Africa: the case for cohort studies. PLos Med. 2010 May 11; 7(5):1000244.

Dalal S, Beunza JJ, Volmink J, Adebamowo C, Bajunirwe F, Njelekela M, Mozaffarian D, Fawzi W, Willett W, Adami HO, Holmes MD. 2011. Non-communicable diseases in sub-Saharan Africa: what we know now. Int J Epidemiol. ; 40(4):885–901.

Kathleen M, Mei Jin MT, Kendall L, Addo J, dos-Santos-Silva I, Quint J, Smeeth L, Cook S, Nitsch D, Natamba B, Xavier Gomez-Olive F, Ako A, Perel P. 2019. Non-communicable diseases in sub-Saharan Africa: a scoping review of large cohort studies. J Glob Health. 2019 Dec; 9(2): 020409.

Fagninou NA, TOUGAN PU, Nekoua M, Fachina R, Koutinhouin GB and Yessoufou A. 2019. Diabetes mellitus: classification, epidemiology, physiopathology, immunology, risk factors, prevention and nutrition. Int. J. Adv. Res. 7(7), 855-863.

Van Belle TL, Coppieters KT, and Von Herrath, MG. 2011. Type 1 Diabetes: Etiology, Immunology, and Therapeutic Strategies. Physiological ReviewsVol. 91, No. 1.

Baynes HW. 2015. Classification, Pathophysiology, Diagnosis and Management of Diabetes Mellitus. J Diabetes Metab 6: 541. doi:10.4172/2155-6156.1000541.

Wylie-Rosett J, Delahanty LM. 2017. Nutrition in the Prevention and Treatment of Disease, (Fourth Edition), Pages 691-707.

Beugré GAM, Niaba KPV, Gnahe DA, Blei SH, Kouamé S, Gnakri D. 2019. Estimated levels of physical activity and food habits in the adolescent in the school environment of the city of Daloa (Côte d'Ivoire). International Journal of Development Research 09 (10): 30686-30693.

OMS. 2020. Travel advice and recommendations during the COVID-19 outbreak.

FAO. 2020. WFP COVID-19: Situation Report #02. 2pp.

Willig A, Wright L, Galvin TA. 2018. Practice Paper of the Academy of Nutrition and Dietetics: Nutrition Intervention and HIV Infection. J Acad Nutr Diet. 2018 Mar; 118(3):486-498. doi: 10.1016/j.jand.2017.12.007.

Weger-Lucarelli J, Garcia SM, Rückert C, Byas A, O'Connor SL, Aliota MT, Friedrich TC, O'Connor DH, Ebel GD. 2018. Taking a bite out of nutrition and arbovirus infection. PLoS Negl Trop Dis. 2018 Mar 29; 12(3):e0006247. doi: 10.1371/journal.pntd.0006247.

Luzi L, Maria GR. 2020. Influenza and obesity: its odd relationship and the lessons for COVID-19 pandemic. ACTA Diabetol. doi: 10.1007/s00592-020-01522-8.

FAO, FIDA, OMS, PAM, UNICEF. 2019. L’État de la sécurité alimentaire et de la nutrition dans le monde 2019. Se prémunir contre les ralentissements et les fléchissements économiques. Rome, FAO. 253p.

Banque Mondiale. 2020. Évaluation de l’impact économique du COVID-19 et des réponses politiques en Afrique Subsaharienne. Afrique Pulse, Volume 21, 1-12p.

CSA. 2012. Comité de la Sécurité Alimentaire Mondiale, S'entendre sur la terminologie, CSA, 39e session, 15-20 octobre 2012, 17 p.

TNWA (Transform Nutrition West Africa). 2020. COVID-19, food and nutrition in West Africa: potential impacts and responses. Consultable à l’adresse:

Williams PG. 2007. Nutritional composition of red meat, Nutrition &Dietetics, 2007, 64(Suppl 4), S113-S119. The definitive version is available & Dietetics is the official journal of the Dietitians Association of Australia. Copyright 2007Blackwell Publishing.

Bohrer BM. 2017. Review: Nutrient density and nutritional value of meat products and non-meat foods high in protein. Trends in Food Science & Technology, Volume 65, July 2017, Pages 103-112.

USDA. 2007. Nutrient Data Research Group. Table of Nutrient Retention Factors. 1-18p.

In Guk Hwang, Young Jee Shin, Seongeung Lee, Junsoo Lee, and Seon Mi Yoo, 2012. Effects of Different Cooking Methods on the Antioxidant Properties of Red Pepper (Capsicum annuum L.). Prev Nutr Food Sci. 2012 Dec; 17(4): 286–292. doi: 10.3746/pnf.2012.17.4.286.

Sun L, Bai X, Zhuang Y. 2014. Effect of different cooking methods on total phenolic contents and antioxidant activities of four Boletus mushrooms. J Food Sci Technol. 2014 Nov; 51(11):3362-8.

Xu F, Zheng Y, Yang Z, Cao S, Shao X, Wang H. 2014. Domestic cooking methods affect the nutritional quality of red cabbage. Food Chem. 2014 Oct 15; 161: 162-7.

WHO/UNICEF Joint Monitoring Programme. 2014. Progress on drinking water and sanitation: 2014 update. 2014 report WHO/UNICEF Joint Monitoring Programme on water supply and sanitation, also known as JMP, Geneva, Switzerland (available at

Piwoz E, Preble E. 2000. HIV/AIDS and nutrition: a review of the literature and recommendations for nutritional care and support in sub-Saharan Africa. Novembre. Agence des Etats-Unis pour le développement international (USAID), Washington. USAID, Support for Research in Africa.

FAO/WHO. 2002. Human vitamin and mineral requirements. Report of a joint FAO/WHO expert consultation. Rome: FAO, 2002.

FAO/OMS. 2003. Vivre au Mieux avec le VIH/SIDA : Un manuel sur les soins et le soutien nutritionnels à l’usage des personnes vivant avec le VIH/SIDA. 102pp.

Tilami SK, Sampels S. 2017. Nutritional Value of Fish:Lipids, Proteins, Vitamins, and Minerals, Reviews in Fisheries Science & Aquaculture, DOI:10.1080/23308249.2017.1399104.

Tougan PU, Dahouda M, Ahounou GS, Salifou CFA, Kpodekon TM, Mensah GA, Kossou NFD, Amenou C, Kogbeto EC, Thewis A, Youssao AKI. 2013a. Effect of breeding mode, type of muscle and slaughter age on technological meat quality of local poultry population of Gallus gallus species of Benin. International Journal of Biosciences 3, 6, 1-17.

Tougan PU, Dahouda M, Salifou CFA, Ahounou GS, Kpodekon TM, Mensah GA, Kossou NFD, Amenou C, Kogbeto EC, Lognay G, Thewis A, Youssao AKI. 2013b. Nutritional quality of meat of local poultry population of Gallus gallus specie of Benin. Journal of Animal and Plant Science. 19, 2, 2908-2922.

Tougan, PU, Dahouda M, CFA Salifou, GS Ahounou, DNF Kossou, C Amenou, CE Kogbeto, MT Kpodekon, GA Mensah, G Lognay, A Thewis, Youssao IAK. 2013. Relationships between technological and nutritional meat quality parameters in local poultry populations (Gallus gallus) of Benin. International Journal of Biological and Chemical Science, Vol 7, No 6: 18p, ISSN 1991-8631.

Tougan Up, Aholou R B , Yayi-Ladekan E, Tchobo PF, Akouegninou A, Hanzen C Koutinhouin GB. 2019a. Qualité technologique et nutritionnelle de la viande des lapins nourris avec des rations contenant des feuilles de Cissus populnea et Synedrella nodiflora et corrélations. International Journal of Biological and Chemical Science, Volume 13, Number 3; Pages 1747-1761.

Tougan UP, Youssao IAK, Yayi EL, Kpodekon MT, Heuskin S, Beckers Y, Mensah GA, Koutinhouin BG, Lognay G, Thewis A. 2018a. Fatty Acids Composition of Meat of Five Native Chicken (Gallus gallus) Ecotypes of Benin Reared under Organic or Conventional system. Journal of Experimental Food Chemistry 4: 137. doi: 10.4172/2472-0542.1000137.

Tougan UP, Yayi-Ladekan E, Alassani AM, Adanlin MP, Koutinhouin GB, Soumanou MM. 2019b. Influence of Follar Organic Fertilizer DI Grow on the Physicochemical and Nutritional Characteristics of Lohman Brown Eggs Reared in Sokode. International Journal of Progressive Sciences and Technologies (IJPSAT), Vol. 17 No. 1, pp. 01-09ISSN: 2509-0119.

Tougan PU. 2016a. Organic free range breeding systems improve the ratio polyunsaturated fatty acids/saturated fatty acid in Fulani and Sahoue indigenous chicken meat of Benin. 3rd European Food Safety & Standards Conference. October 24-25, 2016 Valencia, Spain. J Food Process Technol. DOI: 10.4172/2157-7110.C1.054.

Tougan PU, Daouda IH, Djenontin JA, Gouwakinnou G, Adakamou SGT, Mekpo LA, Mensah GA, Koutinhouin GB, Beckers Y, Sindic M, Thewis A. 2018b. Aptitudes fromagères et beurrières et qualité technologique du lait des vaches de races Borgou et Azawak élevées sur pâturage naturel au Bénin. Bulletin de la Recherche Agronomique du Bénin (BRAB) Numéro spécial Elevage & Faune – Décembre 2018. BRAB en ligne (on line) sur le site web; ISSN sur papier (on hard copy) : 1025-2355 et ISSN en ligne (on line) : 1840-7099.

Tougan PU, Bonou AG, Gbaguidi T, Koutinhouin GB, Ahounou S, Salifou CFA, Zannou MS, Mensah GA, Beckers Y, Everaert N, Théwis A, Youssao AKI. 2016b. Influence of Feed Withdrawal Length on Carcass Traits and Technological Quality of Indigenous Chicken Meat Reared Under Traditional System in Benin. Journal of World's Poultry Research 6(2): 37-47.

Tougan UP, Pomalegni CB, Nago SGA, Théwis A, Mensah GA. 2014. Variabilité de la qualité nutritionnelle et de la composition en acide gras de la viande d’aulacodes (Thryonomys swinderianus, Temminck, 1827) élevées au sud-Benin en relation avec la ration alimentaire. Annales de L’Université de Parakou. Série « Sciences Naturelles et Agronomie » vol.4, No.1 : 53-59. ISBN/ISSN: 678-99919-62-55-9.

Fabbri ADT, Crosby GA. 2016. A review of the impact of preparation and cooking on the nutritional quality of vegetables and legumes. International Journal of Gastronomy and Food Science ; Volume 3, April 2016, Pages 2-11.

Malaisse F, 1997. Se nourrir en forêt claire africaine: Approche écologique et nutritionnelle. 384p. ISBN 2-87016-045-3.

Barasi ME, 2003. Human nutrition: a health perspective. Taylor & Francis group. International Standard Book Number: 978-0-340-81025-5. 397pp.

Willett WC. 2008. Overview and perspective in human nutrition. Asia Pac J Clin Nutr 2008; 17 (S1): 1-4.

González-Gross M, Valtueña J, Breidenassel C, Moreno LA, Ferrari M, Kersting M, De Henauw S, Gottrand F, Azzini E, Widhalm K, Kafatos A, Manios Y, Stehle P. 2011. Vitamin D status among adolescents in Europe: the Healthy Lifestyle in Europe by Nutrition in Adolescence study. Br Journal Nutrition 17: 1-10.

Ziegler EE, Ziegler EE. 2011. Meeting the Nutritional Needs of the Low-Birth-Weight Infant. Ann Nutr Metab 2011; 58 (suppl 1):8–18.

USDA. 2020. National Nutrient Database for Standard Reference 27 Software v.2.1.5.

He FJ, Nowson CA, Lucas M, MacGregor GA. 2007. Increased consumption of fruit and vegetables is related to a reduced risk of coronary heart disease: metanalysis of cohort studies Hum J.. Hypertens., 21 (2007), pp. 717-728.

Zhao L. 2010. Nutrition and safety characteristics of low temperature cooking and traditional diet. China standardization, 9: 16–19.

Tiwari U, Cummins E. 2013. Factors influencing levels of phytochemicals in selected fruit and vegetables during pre- and post-harvest food processing operations. Food Res. Int., 50 (2), pp. 497-506.

Karmas E, Harris RS. 1988. Nutritional Evaluation of Food Processing (third ed), Van Nostrand Reinhold, New York (1988).

Prodanov M, Sierra I, Vidal-Valverde C. 2004. Influence of soaking and cooking on the thiamin, riboflavin and niacin contents of legumes. Food Chem., 84 (2) (2004), pp. 271-277.

Hornero-Mendez D, Minguez-Mosquera M. 2007. Bioaccessibility of carotenes from carrots: Effect of cooking and addition of oil. Innovative Food Science and Emerging Technologies. 8: 407-412.

De Smet S. 2012. Meat, poultry, and fish composition: Strategies for optimizing human intake of essential nutrients. Animal Frontiers, Volume 2, Issue 4, October 2012, 10–16p.

Worthington V. 2001. Nutritional quality of organic versus conventional fruits, vegetables, and grains. J. Alt. Comp. Med. 7: 161-173.

Ismail A, Fun CS. 2003. Determination of vitamin C, -carotene and riboflavin contents in five green vegetables organically and conventionally grown. Mal. J. Nutr. 9: 31-39.

Tarwadi K, Agte V. 2005. Antioxidant and micronutrient quality of fruit and root vegetables from the Indian subcontinent and their comparative performance with green leafy vegetables and fruits. J. Sci. Food Agric. 85: 1469-1476.

Toor RK, Savage GP, Anuschka H. 2006. Influence of different types of fertilizers on the major antioxidant components of tomatoes. J. FoodComp. Anal. 19: 20-27.

Rickman JC, Barrett DM, Bruhn CM. 2007. Review: Nutritional comparison of fresh, frozen, and canned fruits and vegetables. Part 1: Vitamin C and B and phenolics compounds. J. Sci. Food Agric. 87: 930-944.

Safefood Consulting Inc. 2007. A summary of the safety and nutritional value of organic food. 10 pages.

Probst Y. 2009. Nutrient Composition of Chicken Meat. Rural Industries Research and Development Corporation, 08 (210); 1-83. ISBN 1741517990; ISSN 1440-6845.

Holland B, Brown JB. 1993. Fish and Fish products. Third supplement to fifth edition of McCance and Widdowson's The Composition of Foods. Royal Society of Chemistry.

Department of Health of England. 2013. Nutrient analysis of fish and fish products: Summary report. 1-28p.

Aquatias S, Arnal J-F, Rivière D, Bilard J, Callède J-P. 2017. Activ-ité physique: contextes et effets sur la santé - Synthèse et recommandations. [Rapport de recherche]Institut national de la santé et de la recherche médicale(INSERM). 2008, 168 p., HAL Id: hal-01570655 ; références bibli-ographiques disséminées. Le rapport intégral dénombre 832 p.

François M, Broutin C, Sokona K. 2002. Fabriquer et distribuer des « nouveaux produits traditionnels » à Dakar. Les micro- et petites entreprises répondent aux « nouvelles attentes » des consommateurs urbains : hygiène et rapidité de préparation d’un produit « naturel ».

CTA. 2003. Les conséquences de l’application des mesures sanitaires et phytosanitaires (SPS) pour les pays ACP, CTA.

Féral F, Coulibaly HA. 2004. Programme spécial régional pour la sécurité alimentaire des États membres de l’UEMOA (PSRSA), rapport de synthèse, projet.

Couturier J. 2006. Les enjeux de la normalisation pour les produits issus de l’agriculture du Sud, ISF, Paris.

Devautour H. 2007. Conditions d’émergence des produits de qualité, séminaire « Les produits alimentaires de qualité liés à l’origine et aux traditions en Méditerranée », FAO – ministère de l’Agriculture du Maroc, novembre, Casablanca.

Hammoudi A. 2008. Normes et organisation de la qualité dans les filières agroalimentaires : application à l’Afrique sub-saharienne, programme d’étude INRA, document de travail, 120p.

FAO et OMS. 2007. Étiquetage des denrées alimentaires. Cinquième édition. Rome, FAO. OMS. 2019; Guiding principles and framework manual for front-of-pack labelling for promoting healthy diets [en ligne]. Genève (Suisse). [référencé le 01 Avril 2020]. ;

Redmond EC, Griffith CJ. 2009. The importance of hygiene in the domestic kitchen: implications for preparation and storage of food and infant formula. Perspect Public Health. 2009 Mar; 129(2):69-76.

Al-Sakkaf A. 2015. Domestic food preparation practices: a review of the reasons for poor home hygiene practices. Health Promot Int. 2015 Sep; 30(3):427-37. Epub 2013 Aug 14.

Chen Y, Wen Y, Song J, Chen B, Ding S, Ding L, Dai J. 2018. The correlation between family food handling behaviors and foodborne acute gastroenteritis: a community-oriented, population-based survey in Anhui, China. BMC Public Health. 2018 Nov 26; 18(1):1290. Epub 2018 Nov 26.

Chen Y, Song J, Chen B, Wang L, Ding S, Ding L, Dai J. 2019. Food Handling Behaviors Associated with Reported Acute Gastrointestinal Disease That May Have Been Caused by Food. J Food Prot (2019) 82 (3): 494–500.

Yuan GF, Sun B, Yuan J, Wang QM. 2009. Effects of different cooking methods on health-promoting compounds of broccoli. J Zhejiang Univ Sci B. 2009 Aug; 10(8):580-8. doi: 10.1631/jzus.B0920051.

Carmody RN, Wrangham RW. 2009. Cooking and the human commitment to a high-quality diet. Cold Spring Harb Symp Quant Biol. 2009; 74:427-34.

Serpen A, Gökmen V, Fogliano V. 2012. Total antioxidant capacities of raw and cooked meats. Meat Sci. 2012 Jan; 90(1): 60-5.

Evenepoel P, Geypens B, Luypaerts A, Hiele M, Ghoos Y, Rutgeerts P. 1998. Digestibility of cooked and raw egg protein in humans as assessed by stable isotope techniques. J Nutr. 1998 Oct; 128(10): 1716-22.

Nimish MS, Shakila RJ. 2010. Effect of different types of heat processing on chemical changes in tuna. J Food Sci Technol. 2010 Mar; 47(2): 174–181. Published online 2010 Apr 10. doi: 10.1007/s13197-010-0024-2.

Hoffman CJ, Zabik ME. 1985. Effects of microwave cooking/reheating on nutrients and food systems: a review of recent studies. J Am Diet Assoc. 1985 Aug;85(8):922-6.

Jiménez-Monreal AM, García-Diz L, Martínez-Tomé M, Mariscal M, Murcia MA. 2009. Influence of cooking methods on antioxidant activity of vegetables. J Food Sci. 2009 Apr; 74(3): H97-H103. doi: 10.1111/j.1750-3841.2009.01091.x.

Veda S, Kamath A, Platel K, Begum K, Srinivasan K. 2006. Determination of bioaccessibility of beta-carotene in vegetables by in vitro methods. Mol Nutr Food Res. 2006 Nov; 50 (11):1047-52.

Fielding JM, Rowley KG, Cooper P, O' Dea K. 2005. Increases in plasma lycopene concentration after consumption of tomatoes cooked with olive oil. Asia Pac J Clin Nutr. 2005; 14(2):131-6.

Zotos A, Kotaras A, Mikras E. 2013. Effect of baking of sardine (Sardina pilchardus) and frying of anchovy (Engraulis encrasicholus) in olive and Sunflower oil on their quality. Food Sci Technol Int. 2013 Feb; 19(1):11-23. doi: 10.1177/1082013212442179.

Fillion L, Henry CJK. 1998. Nutrient losses and gains during frying: a review. Int J Food Sci Nutr. 1998 Mar; 49(2):157-68.

Maria D, Guillén PS. 2012. Uriarte. Aldehydes contained in edible oils of a very different nature after prolonged heating at frying temperature: Presence of toxic oxygenated a,ß unsaturated aldehyde. Food Chem., 131(3): 915–926.

Dansou PI, Ahounou FJI, Ahissou H, Tossou R. 2008. Les indices de nature de la sauce frite «JA» et la santé du consommateur. Rev. CAMES – Série A, 6: 10-11.

Gondé P, Morin O. 2012. Optimisation du choix de l’huile en friture industrielle: l’exemple Mc Cain, J. OCL.; 19(2) : 96-100.

Vanessa P. 2015. Développement d’antioxydants pour les huiles de friture et contribution à l’étude du mécanisme de formation des monomères cycliques à partir d’acides gras oméga-3. Mémoire, Maîtrise en sciences et technologie des aliments, Université Laval Québec, Canada.

Delagoutte C. 2007. Huiles de friture et dangers, La Cuisine Collective; N°205, p. 58-60.

Gertz C. 2005. Quality control and safety of cooking oils. Frankfurt : Workshop Deep-Frying. 2005.

Gokmen V, Senyuva H. 2007. Acrylamide formation is prevented by divalent cations during the Maillard reaction. Food Chem., 103: 196-203.

Lues JFR, Rasephei MR, Venter P, Theron MM. 2006. Assessing food safety and associated food handling practices in street food vending. Int. J. Env. Health Res., 165(5): 319-328. DOI: 10.1080/09603120600869141.

Morrison JA, Glueck CJ, Wang P. 2008. Dietary trans fatty acid intake is associated with increased fetal loss. Fertil. Steril; 90(2): 385-390.

Ziaiifar A. 2008. Oil Absorption During Deep-fat Frying: Mechanisms and Important Factors, Thèse (Ph. D.), Institut des Sciences et Industries du Vivant et de l’Environnement (Agro Paris Tech), 156 p.

Nishida C, Uauy R. 2009. WHO Scientific Update on trans fatty acids. EJCN; 63: Suppl2.

Lee JG, Kim SY, Moon JS, Kim SH, Kang DH, Yoon HJ. 2016. Effects of grilling procedures on levels of polycyclic aromatic hydrocarbons in grilled meats. Food Chem. 2016 May 15; 199:632-8.



  • There are currently no refbacks.

Copyright (c) 2020 Ulbad Polycarpe TOUGAN

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.