Table 1. Participants in study of antibodies against Cryptosporidium in drinking water, Scotland, UK, 2006–2008.

Participants	Study period
	1 (2006 Apr–Jul)	2 (2006 Aug–Oct)	3 (2008 Apr–Jul)	4 (2008 Aug–Oct)
Previous participants*	1,051	750	608	911
New recruits	0	133	253	0
Total	1,051	883	861	911
By city
Glasgow	791	671	638	698
Dundee	260	212	223	213

*Donated blood at least 1 time since period 1.