**1. Introduction**

It has been firmly established that the Earth is warming, which is shown by the increase in the average ocean temperature and air temperature, and in the melting of snow and ice. Global climate change is one of the most widely discussed topics, not only in the field of climate science or policy making, but also in a range of health researches [1,2]. It can affect human health via different pathways of complexity, directness, and scale [3–5]. A better understanding of the human health dimensions of climate change is necessary for protecting people from climate-sensitive hazards and the development of a sustainable coping strategy [6–9]. In particular, the direct and indirect impact of climate change on infectious diseases has been regarded as one of most urgent research topics [10–12]. It has been well accepted by the academic community that climate change could not only affect the pathogens' ecology and the transmission dynamics of infectious diseases, but also the development of health promotion-related policy and the implementation process of the Sustainable Development Goals [13–15].

In the above-mentioned background, over the past several decades, there has been a large increase in scientific investigations about climate change and infectious diseases [14–16]. For example, the effect of global warming on vector-borne diseases, especially malaria, has been actively investigated [17–22]. The temperature can directly affect the biology of vectors and parasites, and increased precipitation may lead to an increase in the number and quality of breeding sites, and affect the availability of resting sites [23–26]. The temporal and spatial changes in climatic variables might affect the vectors, intermediate hosts, and, consequently, the risk of disease transmission [27,28]. Evidence has also indicated the impact of inter-annual and inter-decadal climate change on vector-borne diseases, which should be explored not only in a continental basis, but also in regional and local basis [29,30].

Bibliometrics is a kind of research method that analyzes bibliographic information using quantitative indicators, and has been widely employed for the statistical analysis of the bibliographic materials in a particular field [31,32]. In view of the impressive progress on climate change and infectious diseases, the quantitative and qualitative assessment of the scientific output will help to know the history, publication trends, research interest, and maturity degree of this field. Thus, the primary aim of the present work was to map the research output and theme trends in climate change and infectious diseases in the last 20 years (from 1999 to 2018), using the bibliometric indicators of production, word co-occurrence biclustering analysis, and strategic diagram. It is anticipated that this kind of reference can help the researchers in this field to prevent repeated work, avoid wasting resources, and know the research trends in the future. For the sake of shorthand, in the following section "this field" refers to "the field related to climate change and infectious diseases".
