1.2 Eligibility criteria

Manuscripts that evaluated the effects of different climatic conditions of temperature and/or humidity on the spread of COVID-19 were included. The search strategy was defined based on the PECOS format as follows:

Population (P): Humans diagnosed with COVID-19;

Exposition (E): Different weather conditions: humidity, temperature;

Comparison (C): Without comparison;

Outcome (O): Spread of SARS-CoV-2 (COVID-19);

Study design (S): Observational studies, prospective or retrospective, case reports, case-series.

The exclusion criteria involved studies that evaluated other upper and lower respiratory tract infections, such as Middle East Respiratory Syndrome Coronavirus (MERS-CoV), SARS-CoV and influenza. The assessment of other climatic conditions, except for temperature and humidity, was also not considered. Opinion articles, animal or laboratory studies, and literature reviews were not included.