Detection rates of norovirus gastroenteritis and factors associated with the infection before and during COVID-19 pandemic: a secondary analysis of surveillance data in Guangxi Zhuang Autonomous Region, Southern China

Figures & data

Figure 1. Detection rates of norovirus gastroenteritis during 2015–2020 in Guangxi Region, China (actual detection rate and prediction rate using ARIMA models in 2020 showed a significant difference by paired t-test, p < 0.001).

Table 1. Annual detection rates of norovirus gastroenteritis during 2015–2020.

Year	No. of gastroenteritis patients	Norovirus-infected patients	Detection rate (95% CI)*
2015	1231	228	18.5 (16.4–20.7)
2016	1200	202	16.8 (14.8–19.0)
2017	1296	140	10.8 (9.1–12.5)
2018	1302	158	12.1 (10.4–13.9)
2019	1397	190	13.6 (11.8–15.4)
2020	1477	90	6.1 (4.8–7.4)
Total	7903	1008	12.8 (12.0–13.4)

*Chi-square test for trend of detection rate from 2015 to 2020= 115.12, p value < 0.001.

Table 2. Characteristics of norovirus gastroenteritis patients during 2015–2020.

Characteristic	No. of gastroenteritis cases n (%) n = 7903	No. of norovirus gastroenteritis patients n (%)
		Positive n = 1008	Negative n = 6895	p value
COVID-19 period				<0.001
Before	6426 (81.3)	918 (91.1)	5508 (79.9)
During	1477 (18.7)	90 (8.9)	1387 (20.1)
Gender				0.249
Female	3657 (46.3)	484 (48.0)	3173 (46.0)
Male	4246 (53.7)	524 (52.0)	3722 (54.0)
Age group (years)				0.001
>45	1843 (23.3)	187 (18.6)	1656 (24.0)
≤5	3299 (41.7)	450 (44.6)	2849 (41.3)
6–20	723 (9.1)	89 (8.8)	634 (9.2)
21–45	2038 (25.8)	282 (28.0)	1756 (25.5)
Types of food^§				<0.001
Grains and grain products	1585 (20.1)	181 (18.0)	1404 (20.4)
Fruits or vegetables	1489 (18.9)	146 (14.5)	1343 (19.5)
Aquatic products	424 (5.4)	65 (6.4)	359 (5.2)
Meat/dairy products	1601 (20.3)	231 (22.9)	1370 (19.9)
Other foods	2797 (35.4)	385 (38.2)	2412 (35.0)
Location of food intake^§				0.425
Home	5846 (77.1)	758 (75.2)	5088 (74.0)
Outside	2041(25.9)	250 (24.8)	1791 (26.0)
Disease history				0.182
Yes	562 (7.1)	61 (6.1)	501 (7.3)
No	7341 (92.9)	947 (93.9)	6394 (92.7)
Antibiotic before seeing doctor				0.170
Yes	539 (6.8)	58 (5.8)	481 (7.0)
No	7364 (93.2)	950 (94.2)	6414 (93.0)
Season when symptoms appeared				<0.001
Spring	1827 (23.1)	248 (24.6)	1579 (22.9)
Summer	2781 (35.2)	264 (26.2)	2517 (36.5)
Autumn	2247 (28.4)	378 (37.5)	1869 (27.1)
Winter	1048 (13.3)	118 (11.7)	930 (13.5)
Time from symptom onset to diagnosis (h)				0.012
<24 h	1832 (23.2)	270 (26.8)	1562 (22.7)
24-48 h	4379 (55.4)	540 (53.6)	3839 (55.7)
>48 h	1692 (21.4)	198 (19.6)	1494 (21.7)
Type of sample				0.750
Anal swab	334 (4.2)	47 (4.7)	287 (4.2)
Stool	7502 (94.9)	952 (94.4)	6550 (95.0)
Gastric fluid	67 (0.8)	9 (0.9)	58 (0.8)
Location of sentinel hospitals				<0.001
Yulin	761 (9.6)	91 (9.0)	670 (9.7)
Guigang	849 (10.7)	107 (10.6)	742 (10.8)
Guilin	1293 (16.4)	219 (21.7)	1074 (15.6)
Liuzhou	2067 (26.2)	254 (25.2)	1813 (26.3)
Nanning	2933 (37.1)	337 (33.4)	2596 (37.7)
Level of hospital				0.039
City	6434 (81.4)	845 (83.8)	5589 (81.1)
Province	1469 (18.6)	163 (16.2)	1306 (18.9)
Hospitalization				0.903
Yes	1944 (24.6)	250 (24.8)	1694 (24.6)
No	5959 (75.4)	758 (75.2)	5201 (75.4)

^§Missing values in type of foods (n = 7); location of food intake (n = 16) which all were in the negative group.

Table 3. Final logistic regression model of factors related to norovirus gastroenteritis (N = 7887).

Variable	cOR (95% CI)	aOR (95% CI)	p value
COVID-19 period (Ref: Before)	0.39 (0.31–0.49)	0.11 (0.04–0.27)	<0.001
Age group (Ref: >45 years)
≤5	1.40 (1.17–1.68)	1.48 (1.22–1.80)	<0.001
6–20	1.24 (0.95–1.62)	1.20 (0.89–1.62)	0.231
21–45	1.42 (1.17–1.73)	1.41 (1.14–1.74)	0.002
Types of food (Ref: Grains and grain products)
Fruits or vegetables	0.84 (0.67–1.06)	0.89 (0.70–1.13)	0.344
Aquatic products	1.40 (1.03–1.90)	1.50 (1.09–2.06)	0.012
Meat/dairy products	1.31 (1.06–1.61)	1.27 (1.02–1.57)	0.031
Other foods	1.24 (1.02–1.49)	1.19 (0.98–1.45)	0.071
Location of food intake (Ref: at home)
Outside	0.94 (0.80–1.09)	0.78 (0.65–0.94)	0.009
Season when symptoms appeared (Ref: Spring)
Summer	0.67 (0.56–0.80)	0.66 (0.55–0.80)	<0.001
Autumn	1.29 (1.08–1.53)	1.38 (1.15–1.65)	<0.001
Winter	0.81 (0.64–1.03)	0.81 (0.64–1.03)	0.086
Time from symptom onset to diagnosis (Ref: <24 h)
24–48 h	0.81 (0.70–0.95)	0.80 (0.68–0.94)	0.007
>48 h	0.77 (0.63–0.93)	0.71 (0.58–0.88)	0.001
Location of sentinel hospitals (Ref: Yulin)
Guigang	1.07 (0.79–1.44)	1.19 (0.87–1.62)	0.280
Guilin	1.51 (1.16–1.96)	1.72 (1.31–2.26)	<0.001
Liuzhou	1.03 (0.80–1.33)	1.16 (0.89–1.51)	0.271
Nanning	0.96 (0.75–1.22)	0.95 (0.74–1.23)	0.712
Interaction terms
Ref: COVID-19 period (before) & Age >45 years
COVID-19 period (during)*Age group (≤5 years)	-	3.03 (1.15–8.01)	0.025
COVID-19 period (during)*Age group (6–20 years)	-	4.72 (1.62–13.81)	0.004
COVID-19 period (during)*Age group (21 - 45 years)	-	2.85 (1.05–7.75)	0.040
Ref: COVID-19 period (before) & food intake at home
COVID-19 period (during)*food intake outside	-	2.19 (1.27–3.78)	0.005

cOR: crude odds ratio; aOR: adjusted OR; CI: confidence interval.

Table 4. Factors associated with detection of norovirus infection stratified by COVID-19 period.

Variable	Norovirus detection before COVID-19			Norovirus detection during COVID-19
	cOR (95% CI)	aOR (95% CI)	p value (Wald’s test)	cOR (95% CI)	aOR (95% CI)	p value (Wald’s test)
Age group (Ref: >45 years)
≤5	1.41 (1.17-1.70)	1.49 (1.23-1.81)	<0.001	3.44 (1.35-8.81)	4.80 (1.80-12.79)	0.002
6–20	1.15 (0.86-1.54)	1.21 (0.89-1.63)	0.222	5.66 (2.03-15.57)	5.68 (2.01-16.06)	0.001
21–45	1.36 (1.11-1.67)	1.40 (1.14-1.74)	<0.001	4.49 (1.71,11.79)	3.77 (1.41-10.05)	0.008
Types of food (Ref: grains and grain products)
Fruits or vegetables	0.87 (0.68-1.12)	0.87 (0.68-1.13)	0.304	0.78 (0.42-1.44)	0.91 (0.47-1.74)	0.771
Aquatic products	1.46 (1.06-2.02)	1.58 (1.13-2.20)	0.007	0.76 (0.25-2.27)	0.90 (0.29-2.80)	0.854
Meat/dairy products	1.26 (1.01-1.58)	1.27 (1.01-1.59)	0.041	1.19 (0.62-2.25)	1.26 (0.64-2.45)	0.503
Other foods	1.28 (1.05-1.57)	1.26 (1.03-1.55)	0.026	0.71 (0.40-1.28)	0.61 (0.32-1.13)	0.117
Location of food intake (Ref: home)
Outside	0.85 (0.72-1.00)	0.78 (0.65-0.94)	0.007	1.87 (1.19-2.93)	1.90 (1.11-3.26)	0.019
Season when symptoms appeared (Ref: spring)
Summer	0.66 (0.54-0.80)	0.65 (0.54-0.79)	<0.001	0.86 (0.46-1.62)	0.75 (0.39-1.44)	0.385
Autumn	1.32 (1.10-1.58)	1.35 (1.12-1.63)	0.002	1.57 (0.87-2.82)	1.87 (1.00-3.49)	0.051
Winter	0.79 (0.62-1.01)	0.81 (0.63-1.03)	0.087	0.92 (0.39-2.17)	1.02 (0.42-2.47)	0.969
Time from symptom onset to diagnosis (Ref: <24 h)
24–48	0.83 (0.70-0.98)	0.81 (0.68-0.96)	0.014	0.72 (0.44-1.19)	0.68 (0.40-1.14)	0.145
>48	0.79 (0.64-0.97)	0.73 (0.59-0.91)	0.005	0.62 (0.33-1.18)	0.54 (0.27-1.08)	0.082
Location of sentinel hospitals (Ref: Yulin)
Guigang	1.17 (0.85-1.61)	1.22 (0.87-1.69)	0.245	0.85 (0.37-1.98)	0.89 (0.35-2.24)	0.803
Guilin	1.61 (1.22-2.14)	1.77 (1.33-2.36)	<0.001	1.08 (0.49-2.36)	1.78 (0.72-4.42)	0.213
Liuzhou	1.06 (0.81-1.39)	1.19 (0.90-1.58)	0.218	0.85 (0.39-1.83)	0.97 (0.43-2.18)	0.938
Nanning	1.01 (0.78-1.32)	1.02 (0.78-1.34)	0.878	0.53 (0.24-1.16)	0.47 (0.20-1.07)	0.070

Data availability statement

Data are available on request due to privacy or other restrictions of the Guangxi Zhuang Autonomous Region Centre for Disease Control and Prevention.