*2.1. Data Collection*

The data from 1999 until 2018 were retrieved from PubMed of the National Library of Medicine on the web (http://www.ncbi.nlm.nih.gov/pubmed), with the medical subject headings (MeSH) terms "Climate Change", "Climate", "Meteorological Concepts", "Weather", and "Communicable Diseases"; the key words "Meteorological" and "Infectious diseases" in the title and abstract fields; and the Boolean combinations of these words as the retrieval strategy (for details of the retrieval strategy, see Table S1 in Supplementary Materials). The literature type was limited to journal articles. All publications were saved as two files, in the format of XML and MEDLINE, separately. Two independent researchers filtered the downloaded records manually according to the inclusion and exclusion criteria, after reviewing the titles and abstracts, and even, in some cases, the full text of the records. If they disagreed, the third person would judge whether a record was relevant. The included records were journal articles concerning both climate change and infectious diseases. The exclusion criteria were the following: (1) books, retracted publications, and bibliographies; (2) records of which the topic was related to political climate, social climate, economic climate, financial climate, organizational climate, etc.; and (3) repeated records.

Aiming to map the knowledge structure and theme trends of climate change and infectious diseases in the last 20 years, two periods of 10 years each were established, namely: 1 January 1999–31 December 2008, and 1 January 2009–31 December 2018. Furthermore, the comparative analysis for articles published in the two periods was conducted from the perspectives of bibliometric indicators and topics.
