Table 1.

Frequency of contacts traced per COVID-19 primary case by district, Tamil Nadu, India, March–May 2020

District	Days since reporting of the first case in the district	# primary cases	Frequency of contacts				Number of contacts tested	Number of contacts tested positive	Secondary attack rate
			# contacts identified	Household contacts	Community contacts	Median (range) contacts per primary case
Chennai	51	530	9731	1795	7936	18 (1–151)	9724	261	3 (2.4–3.0)
Coimbatore	33	151	3257	570	2687	22 (1–274)	1585	151	10 (8.2–11.1)
Erode	46	56	1032	246	786	18 (3–141)	1032	38	4 (2.7–5.0)
Karur	15	42	416	271	145	10 (1–86)	416	18	4 (2.8–6.7)
Ranipet	25	29	273	153	120	9 (1–68)	273	11	4 (2.3–7.1)
Tirunelveli	23	35	166	157	9	5 (1–21)	145	20	14 (9.1–20.0)
Tirupathur	20	12	312	61	251	26 (1–100)	312	5	2 (0.7–3.7)
Tiruppur	24	66	279	241	38	5 (1–10)	279	80	29 (23.7–34.0)
Vellore	23	10	236	51	185	24 (6–79)	236	15	6 (3.9–10.0)
Overall		931	15 702	3545	12 157	17 (5–26)	14 002	599	4 (4.0–4.6)