A literature review was conducted by searching the materials published in databases including Web of Science, PubMed, Google Scholar search engine and, the WHO website. 
Web of Science
A literature review was conducted by searching the materials published in databases including Web of Science, PubMed, Google Scholar search engine and, the WHO website. 
PubMed
A literature review was conducted by searching the materials published in databases including Web of Science, PubMed, Google Scholar search engine and, the WHO website. 
Google Scholar search engine
A literature review was conducted by searching the materials published in databases including Web of Science, PubMed, Google Scholar search engine and, the WHO website. 
the WHO website