Epidemiology of Coronavirus Disease in Gansu Province, China, 2020

Jingchun Fan; Xiaodong Liu; Weimin Pan; Mark W. Douglas; Shisan Bao


Emerging Infectious Diseases. 2020;26(6):1257-1265. 

In This Article


Patient Characteristics

Of the total 54 cases of COVID-19 in Gansu Province, 35 were imported primary and 19 were indigenous secondary cases. Serious/critical illness was experienced by 6 (17.1%) of the 35 patients with primary cases and by 3 (15.7%) of the 19 patients with secondary cases; the difference was not significant (p = 0.899). A total of 24 cases were reported during the early period and 30 during the late period (Figure 3). On January 26, the first secondary case of COVID-19 was identified in Longnan, a city located in southern of Gansu Province. The youngest patient was 1 year and 8 months of age; the oldest was 94 years of age. We used Cox proportional hazards regression to correct for covariates but found no significant differences between the early and late groups. No survival pattern could be calculated because, to date, no COVID-19–associated deaths in Gansu Province have been reported.

Figure 3.

Time series of coronavirus disease case identification in Gansu Province, China, 2020.

Comparing patients who sought care in the early and late periods, we found significant differences for age (median age 34 years for the early period vs. 48 years for the late period; p = 0.014) and for occupation (more laborers in the early period vs. more retired persons in the late period; p = 0.009) but not for patient sex or whether the patients lived in urban or rural areas (Table 1). In addition, more case-patients in the early period had visited epidemic areas (p = 0.043) and returned to their destination (p = 0.024) than had patients in the late period.

Key Time-to-event Distributions of COVID-19

For the 54 cases of COVID-19 diagnosed in Gansu Province from January 23 through February 3, the days from illness onset to first medical visit ranged from 0 to 10 and the days from first medical visit to hospitalization ranged from 0 to 7. The days from infection to symptom onset for 19 case-patients in a family cluster, confirmed by epidemiologic survey, ranged from 2 to 10 days (mean 6.7 days); the 95th percentile of the distribution was 12.5 days (95% CI 9.2–18 days) (Table 2; Figure 4, panel A). Among the 24 COVID-19 cases confirmed in the early period, the estimated mean time from illness onset to first medical visit was 2.8 days (95% CI 1.7–3.8); that is, there was a trend toward longer delay for case-patients in the early period than the mean of 2.3 days (95% CI 1.3–3.2) for the 30 case-patients in the late period (Figure 4, panel B), but this difference did not reach statistical significance (p>0.05). The mean duration from first medical visit to hospital admission was 1.9 days (95% CI 1.2–2.6 days) among 24 case-patients with illness onset during the early period, shorter than among 30 case-patients with illness onset during the second period, among whom the mean duration from first medical visit to hospital admission was 3.3 days (95% CI 2.7–4.0 days) (Figure 4, panel C).

Figure 4.

Key time-to-event distributions of coronavirus disease cases in Gansu Province, China, 2020. A) Incubation period (i.e., days from infection to illness onset). B) Days from illness to first medical visit. C) Days from illness to hospitalization.

Spatial Distribution of COVID-19

The 54 COVID-19 cases reported in Gansu Province from January 23 through February 3 were distributed in 11 prefectures and 24 counties. The 2 cities with the most COVID-19 case-patients were Lanzhou (26 cases) and Tianshui (8 cases). The area with the most COVID-19 cases was Chengguan District, the political and economic center of Lanzhou (Figure 5, panel A). Patients with secondary cases seem to have been infected by persons with primary cases; we identified 6 family clusters: 3 in Lanzhou, 1 in Tianshui, 1 in Longnan, and 1 in Linxia. LISA analysis demonstrated hot spots (high-high) and outliers (high-low and low-high). The high-high cluster included 4 counties, accounting for 4.55% of all counties, mainly distributed in the eastern capital city of Lanzhou. High-low and low-high outliers were sporadically distributed in eastern-central Gansu Province (Figure 5, panel B).

Figure 5.

Distribution of reported coronavirus disease cases (A) and local indicators of spatial association cluster map (B) for Gansu Province, January 23–February 3, 2020. Numbers in parentheses indicate number of counties.