Table 3.

Association of environmental factors with MERS, SARS, and COVID-19

Factor	MERS		SARS		COVID-19 #
	Range	RR (95%CI)	Range	RR (95%CI)	Range	RR (95%CI)
Average temperature (°C)	8.56~27.00	1.94 (1.23~3.04)*	−3.07~14.00	2.94 (1.07~8.05)*	−20.43~5.00	7.60 (2.58~22.42)*
	27.00~39.17	0.87 (0.60~1.25)	14.00~31.40	0.18 (0.13~0.26)*	5.00~27.00	0.24 (0.23~0.26)*
					27.00~38.89	1.09 (0.64~1.86)
Temperature range (°C)	5.72~13.50	2.28 (1.45~3.59)*	3.39~10.00	0.06 (0.02~0.17)*	2.74~13.50	0.51 (0.40~0.65)*
	13.50~18.61	0.89 (0.59~1.32)	10.00~12.00	1.06 (0.99~1.12)	13.50~19.03	1.79 (1.15~2.79)*
			12.00~20.36	0.00 (0.00~0.04)*
Relative humidity (%)	8.38~42.00	1.46 (1.38~1.55)*	22.27~94.11	0.01 (0.00~0.02)*	10.39~93.27	2.26 (1.56~3.28)*
	42.00~90.92	0.27 (0.09~0.79)*
Wind speed (m/s)	0.10~2.80	3.49 (1.03~11.85)*	0.80~2.60	17.88 (5.07~63.06)*	0.40~9.30	0.73 (0.60~0.90)*
	2.80~6.60	0.01 (0.00~0.04)*	2.60~7.40	0.01 (0.00~138.62)
Precipitation (mm)	0.00~16.00	3.45 (0.52~22.95)	0.00~13.00	0.00 (0.00~0.01)*	0.00~42.00	0.30 (0.12~0.76)*
Visibility (km)	4.28~8.50	0.48 (0.42~0.54)*	0.00~13.00	9.49 (2.92~30.81)*	3.59~14.00	1.71 (1.51~1.94)*
	8.50~16.00	6.01 (4.09~8.82)*	13.00~29.15	0.14 (0.02~0.86)*	14.00~33.00	0.33 (0.26~0.41)*
	16.00~19.79	0.32 (0.12~0.83)*			33.00~43.71	1.09 (0.51~2.31)
Leaf area index	0.34~15.38	0.45 (0.07~3.03)	0.80~10.50	23.26 (17.67~30.62)*	0.43~35.00	0.69 (0.68~0.69)*
			10.50~20.00	0.10 (0.04~0.25)*	35.00~63.68	1.10 (0.85~1.44)
			20.00~29.63	89.23 (62.53~127.33)*

Note: MERS Middle East respiratory syndrome. SARS severe acute respiratory syndrome

COVID-19 coronavirus disease 2019

RR relative risk. CI confidence interval

^#The government response index from the Oxford COVID-19 Government Response Tracker (OxCGRT) was adjusted in the model

*p<0.05