Across the 31 provinces and regions in mainland China, the mean daily search index at the national level for Covid-19 related terms was 4, 533 (IQR (Interquartile Range) =1, 301) before the outbreak (January 1 2017 to December 30 2019), and 314, 718 (IQR=445, 074) after the outbreak (December 31 2019 to March 15 2021). The median provincial level search index ranged from 63 (IQR=7) in Tibet to 1,138 (IQR=302) in Guangdong before Covid-19, and ranged from 1,186 (IQR=983) in Tibet to 38, 061(IQR=45, 785) in Guangdong. The crude relative change in the median of search index ranged from 2 099% in Tibet and 2 034% in Hainan to 3 872% in Beijing and 4 294% in Liaoning (Table 1). 89, 936 cases of SARS-COV-2 occurred nationwide (including 1 case in Tibet and 68, 021 in Hubei) from 31 December 2020 to March 15 2021. The number of confirmed cases outside Tibet and Hubei ranged from 18 (0.1%) in Qinghai to 2, 245 (10.6%) in Guangdong province. In conjunction with these search patterns, 13%, 76% and 11% of confirmed Covid-19 cases were reported in January 2020, February 2020 and from March 2020 to March 2021 respectively.
Table 1
Comparison of search index in the COVID-19 and pre-COVID period
| | Pre-Covid-19 Period (Jan 1 2017- Dec 30 2019) | | Covid-19 Period (Dec 31 2019- Mar 15 2021) | | Relative Change (%) |
| | Median | IQR | | Median | IQR | |
Low HDI | | | | | | | | |
| Tibet | 63 | 7 | | 1386 | 983 | | 2099 |
| Yunnan | 290 | 79 | | 7939 | 7612 | | 2642 |
| Guizhou | 224 | 87 | | 7011 | 6531 | | 3030 |
| Gansu | 175 | 74 | | 5304 | 6348 | | 2931 |
| Qinghai | 73 | 33 | | 2465 | 1625 | | 3277 |
| Xinjiang | 176 | 56 | | 6108 | 7744 | | 3370 |
| Guangxi | 303 | 119 | | 7548 | 9863 | | 2391 |
| Sichuan | 536 | 167 | | 15792 | 19522 | | 2846 |
| Anhui | 324 | 124 | | 11199 | 13205 | | 3356 |
| Ningxia | 86 | 59 | | 2569 | 2019 | | 2887 |
Middle HDI | | | | | | | |
| Jiangxi | 274 | 96 | | 8021 | 8726 | | 2827 |
| Henan | 489 | 152 | | 15319 | 17469 | | 3033 |
| Hebei | 435 | 152 | | 18986 | 26505 | | 4270 |
| Hunan | 348 | 124 | | 11216 | 13615 | | 3123 |
| Shanxi | 263 | 84 | | 8674 | 11963 | | 3198 |
| Hainan | 157 | 53 | | 3351 | 2709 | | 2034 |
| Chongqing | 272 | 97 | | 7965 | 8692 | | 2828 |
| Heilongjiang | 279 | 88 | | 10902 | 15782 | | 3808 |
| Shaanxi | 356 | 116 | | 9111 | 11704 | | 2463 |
| Hubei | 404 | 137 | | 10723 | 11385 | | 2554 |
| Fujian | 462 | 155 | | 10842 | 11205 | | 2247 |
| Inner Mongolia | 207 | 72 | | 6747 | 8116 | | 3167 |
| Jilin | 234 | 76 | | 9375 | 12607 | | 3906 |
High HDI | | | | | | | | |
| Shandong | 597 | 210 | | 21802 | 31866 | | 3555 |
| Guangdong | 1138 | 302 | | 38061 | 45784 | | 3246 |
| Liaoning | 365 | 144 | | 16001 | 24060 | | 4284 |
| Zhejiang | 754 | 250 | | 22516 | 26850 | | 2886 |
| Jiangsu | 789 | 253 | | 23453 | 30053 | | 2874 |
| Tianjin | 247 | 84 | | 7516 | 8409 | | 2943 |
| Shanghai | 622 | 194 | | 16430 | 19065 | | 2541 |
| Beijing | 647 | 204 | | 25699 | 36265 | | 3872 |
Model Estimated change of search index by HDI categories.
As shown in Table 2, there was a 10% (relative risk (RR)=1.10, 95% CI: 1.07-1.13, p<.0001), 11% (RR=1.11, 95% CI: 1.08-1.14, p<.0001) and 13% (RR=1.13, 95% CI: 1.10-1.16, p<.0001) annual increase in the research index before the pandemic among regions with low, middle and high HDI respectively. The difference in pre-Covid-19 trends of the search index among the three HDI groups was not statistically significant (middle vs. low, ratio of RR=1.01, p=0.6188; high vs. low, ratio of RR=..03, p=0.2239) (Table 2, Figure 1).
Table 2
Model estimated change of search index by HDI categories
| Regions with Low HDI | | Regions with Middle HDI | | Regions with High HDI |
| RR (95% CI) | p-value | Ratio of RR | | RR (95% CI) | p-value | Ratio of RR* | p-value | | RR (95% CI) | p-value | Ratio of RR* | p-value |
Pre-pandemic | | | | | | | | | | | | | |
Yearly change Jan 1 2016 - Dec 30 2019 | 1.10 (1.07, 1.13) | <.0001 | Reference | | 1.11 (1.08, 1.14) | <.0001 | 1.01 (0.97, 1.05) | .6188 | | 1.13 (1.10, 1.16) | <.0001 | 1.03 (0.98, 1.07) | .2239 |
Initial COVID-19 Wave | | | | | | | | | | | | | |
Level Change on Dec 31 2019 | 1.41 (1.34, 1.49) | <.0001 | Reference | | 1.62 (1.54, 1.70) | <.0001 | 1.15 (1.07, 1.23) | .0002 | | 1.58 (1.48, 1.68) | <.0001 | 1.12 (1.03, 1.21) | .0091 |
Level change Jan 18 (HHT announced) - Jan 25 2020 (lockdown) | 106.80 (100.07, 113.99) | <.0001 | Reference | | 124.55 (117.61, 131.90) | <.0001 | 1.16 (1.07, 1.27) | .0004 | | 125.31 (116.53, 134.75) | <.0001 | 1.17 (1.06, 1.30) | .0012 |
Weekly change Jan 25 - Jun 10 2020 | 0.90 (0.89, 0.90) | <.0001 | Reference | | 0.89 (0.88, 0.89) | <.0001 | 0.99 (0.98, 0.99) | <.0001 | | 0.89 (0.89, 0.90) | <.0001 | 0.99 (0.99, 1.00) | .0768 |
Beijing Outbreak | | | | | | | | | | | | | |
Level change Jun 11- Jun 17 2020 | 1.91 (1.79, 2.03) | <.0001 | Reference | | 1.34 (1.26, 1.42) | <.0001 | 1.01 (0.94, 1.10) | .7419 | | 2.12 (1.98, 2.27) | <.0001 | 1.11 (1.01, 1.21) | .0227 |
Weekly change Jun 17 - Oct 11 2020 | 0.96 (0.95, 0.96) | <.0001 | Reference | | 1.02 (1.01, 1.02) | <.0001 | 0.99 (0.98, 1.00) | .0059 | | 0.94 (0.93, 0.94) | <.0001 | 0.98 (0.97, 0.99) | <.0001 |
Qingdao Outbreak | | | | | | | | | | | | | |
Level Change on Oct 12th | 1.31 (1.23, 1.40) | <.0001 | Reference | | 1.34 (1.26, 1.42) | <.0001 | 1.02 (0.93, 1.11) | .6979 | | 1.41 (1.31, 1.52) | <.0001 | 1.07 (0.97, 1.18) | .1693 |
Weekly change in winter wave Oct 12 2020 - Jan 3 2021 | 1.01 (1.00, 1.01) | 0.0647 | Reference | | 1.02 (1.01, 1.02) | <.0001 | 1.01 (0.99, 1.02) | .1043 | | 1.02 (1.01, 1.03) | .0002 | 1.01 (0.99, 1.02) | .1058 |
Shijiazhuang Outbreak | | | | | | | | | | | | | |
Level change Jan 3- Jan 7 2021 | 2.00 (1.85, 2.16) | <.0001 | Reference | | 2.67 (2.50, 2.86) | <.0001 | 1.34 (1.21, 1.48) | <.0001 | | 2..45 (2.24, 2.67) | <.0001 | 1.22 (1.09, 1.37) | .0007 |
Weekly change Jan 7- Mar 15 2021 | 0.83 (0.82, 0.84) | <.0001 | Reference | | 0.80 (0.79, 0.80) | <.0001 | 0.95 (0.94, 0.97) | <.0001 | | 0.78 (0.77, 0.79) | <.0001 | 0.94 (0.93, 0.96) | <.0001 |
* In reference to the low HDI category |
During the initial wave, the search index increased by 41%, 62% and 58% on December 31, 2019 among regions with low (RR=1.41, 95% CI: 1.34-1.49, p<.0001), middle (RR=1.62, 95% CI: 1.54-1.70, p<.0001) and high (RR=1.58, 95% CI: 1.48-1.68, p<0.0001) HDI, respectively. The immediate increase in middle and high HDI regions was statistically significantly higher than the increase in low HDI regions (middle vs. low, ratio of RR=1.15, p=.0002; high vs. low, ratio of RR=1.12, p=.0091). Similarly, there was a 107-fold, 125-fold and 125-fold increase in search index between January 18 and January 25 2020, the period shortly after the official announcement of human-to-human transmission (HHT), among regions with low (RR=106.8, 95% CI:100.1-114.0, p<.0001), middle (RR=124.6, 95% CI: 117.6-131.9, p<.0001) and high (RR=125.3, 95% CI: 116.5-134.8, p<.0001) HDI, respectively. The immediate increase in this short period among middle and high HDI regions were statistically significantly higher than the increase in low HDI regions (middle vs. low, ratio of RR=1.16, p=.0004; high vs. low, ratio of RR=1.17, p=.0012). From the peak of the search index on January 25 to June 10 2020, a 10%, 11% and 11% decrease per week was observed in the search index among regions with low (RR=0.90, 95% CI: 0.89-0.90, p<.0001), middle (RR=0.89, 95% CI: 0.88-0.89, p<.0001) and high (RR=0.89, 95% CI: 0.89-0.90, p<.0001) HDI, respectively (Table 2).
The outbreak in Beijing was associated with a 91%, 34% and 112% increase in the search index among regions with low (RR=1.91, 95% CI: 1.79-2.03, p<.0001), middle (RR=1.34, 95% CI: 0.94-1.10, p<.0001) and high (RR=2.12, 95% CI: 1.98-2.27, p<.0001) HDI, respectively, in the first week (June 11-17 2020) of the outbreak. Additionally, the Beijing outbreak was associated with an increase in the monthly change rate of the search index. From June 17 to October 11 2020, a 4% decrease, 2% increase and 6% decrease per month in the search index was observed among regions with low (RR=0.96, 95% CI: 0.95-0.96, p<0.0001), middle (RR=1.02, 95% CI: 1.01-1.02, p<.0001) and high (RR=0.94, 95% CI: 0.93-0.94, p<.0001) HDI, respectively (Table 2).
The Qingdao outbreak was associated with a comparable 31%, 34% and 41% immediate increase in the search index among regions with low (RR=1.31, 95% CI: 1.23-1.40, p<.0001), middle (RR=1.34, 95% CI: 1.26-1.42, p<.0001) and high (RR=1.41, 95% CI: 1.31-1.52, p<.0001) HDI, respectively. In the winter wave after the Qingdao outbreak, search index increased by 1%, 2% and 2% per week among regions with low (RR=1.01, 95% CI: 1.00-1.01, p=.0647), middle (RR=1.02, 95% CI: 1.01-1.02, p<0.0001) and high (RR=1.02, 95% CI: 1.01-1.03, p=.0002) HDI, respectively.
The Shijiazhuang outbreak in January 2021 was associated with a 167% and 145% immediate increase in search index among ) regions with middle (RR=2.67, 95% CI: 2.50-2.86, p<0.0001) and high (RR=2.45, 95% CI: 2.24-2.67, p<.0001) HDI, respectively, higher than the 100% increase (RR=2.00, 95% CI: 1.85-2.16, p<.0001) in regions with low HDI (middle vs. low, ratio of RR=1.34, p<.0001; high vs. low, the ratio of RR=1.22, p=.0007). However, the 20% and 22% weekly decrease in search index after the Shijiazhuang outbreak among regions with middle (RR=0.80, 95% CI: 0.79-0.80, p<.0001) and high (RR=0.78, 95% CI: 0.77-0.79, p<.0001) HDI, respectively, was statistically significantly greater (p<.0001) than the 17% monthly decrease in the region with low HDI (RR=0.83, 95% CI: 0.82-0.84, p<.0001). Figure 2 illustrated the heterogeneity in the immediate relative change in the search index following each pre-specified exposure across the country.
Association between HDI, CNPPP, education, life expectancy and magnitude of change in the search index.
The results from models where HDI or its component was coded as a continuous variable were consistent with findings from our main analysis. As shown in Table S1, the pre-pandemic trends in two provinces differing in HDI, GNPPP education year or life expectancy by one standard deviation were similar (p>0.1). The immediate relative increase in the search index in a province with one standard higher HDI was statistically higher (initial wave: Ratio of RR=1.09, p<.0001; HHT announcement: Ratio of RR=1.04 p=.0395; Beijing outbreak: Ratio of RR=1.06, p= .0090; Qingdao outbreak: Ratio of RR=1.04, p=0.0324; Shijiazhuang outbreak: Ratio of RR=1.11, p<0.0001). In contrast, the gradual decrease in the search index in a province with one standard higher HDI after each exposure was either similar or greater. For each exposure, the difference associated with GNPPP, education year or life expectancy in the directions and magnitudes of both immediate and gradual effect across provinces was similar to the difference associated with HDI.