Table 1.

Summary of reported index cases from 1 January 2015 to 30 April 2020, in Zanzibar

	2015	2016	2017	2018	2019	2020*
Cases notified by health facilities	4325	3856	4252	5494	6766	6678
No of index cases followed up to health facilities by DMSOs	3745	2596	2940	3647	5747	4011
No of investigated index cases (%)	2592† (69.2)	2096 (80.7)	2081 (70.8)	2736 (75.0)	4259 (74.1)	2630 (65.6)
Median age (years) of investigated index cases	20 (IQR: 11–29)	19 (IQR: 9–28)	21 (IQR: 13–29)	20 (IQR: 11–29)	22 (IQR: 13–31)	23 (IQR: 15–31)
Fraction of investigated index cases who were male (%)	59.3	57.6	62.6	59.3	64.8	69.8
Fraction of investigated index cases reported in Unguja (%)	81.6	69.7	84	77.1	82.9	80.2
No of index cases with travel history outside Zanzibar (%)	1926 (51.4)	1195 (46.0)	1223 (41.6)	1938 (53.1)	3536 (61.5)	1365 (34.0)
No of index cases with travel history within Zanzibar (%)	139 (3.7)	87 (3.4)	87 (3.0)	154 (4.2)	197 (3.4)	220 (5.5)
No of index cases with no travel history outside their shehia (%)	1680 (44.9)	1314 (50.6)	1630 (55.4)	1555 (42.6)	2014 (35.0)	2426 (60.5)
‡Fraction of index cases reported during January–April who have travel history outside Zanzibar	62.7	51.0	55.2	58.6	69.0	35.1
‡Fraction of index cases reported during January–April who have travel history within Zanzibar	4.4	4.9	3.0	4.6	3.0	5.7
Weekly rainfall year in mm (median (IQR))	9.8 (1.9–30.7)	2.9 (0.0–18.3)	15.5 (3.1–72.6)	21.8 (6.9–63.5)	16.6 (2.4–88.9)	10.9 (6.0–12.9)
Weekly rainfall during the masika season in mm, mid-March to May (median (IQR))	52.4 (12.5–96.3)	19.8 (3.7–55.1)	125.6 (62.7–175.7)	56.3 (25.2–129.3)	43.3 (13.3–84.6)	–
Weekly rainfall during the vuli season in mm, November to mid-January (median (IQR))	11.8 (4.5–43.8)	13.3 (2.6–19.3)	19.2 (9.1–66.3)	17.9 (9.9–24.8)	43.8 (15.7–74.4)	–

*Time period 1 January to 30 April.

†Data available from 1 January to 16 September.

‡Calculated to make comparison among all years from 2015 to 2020.

DMSO, District Malaria Surveillance Officer.