Due to its extensive polymorphism, a partial sequence of the Cryptosporidium surface glycoprotein gene gp60 has been frequently used as a genetic marker. I explored the global diversity of this protein, and compared its sequence diversity in Cryptosporidium parvum and Cryptosporidium hominis. In marked contrast to the geographical partition of C. parvum and C. hominis multi-locus genotypes, gp60 allelic groups showed no evidence of segregating in space, or of differing with respect to geographical diversity. Globally, genetic diversity of C. hominis gp60 exceeded that of C. parvum. Within C. parvum, gp60 alleles originating from human isolates were more diverse than those infecting ruminants. Phylogenetic analysis grouped gp60 sequences into a small number of relatively homogenous allelic groups, with only a small number of alleles having evolved independently. With the notable exception of a group of alleles restricted to humans, C. parvum alleles are found in ruminants and humans.

Foodborne outbreaks of cryptosporidiosis are uncommon. In Denmark human cases are generally infrequently diagnosed. In 2005 an outbreak of diarrhoea affected company employees near Copenhagen. In all 99 employees were reported ill; 13 were positive for Cryptosporidium hominis infection. Two analytical epidemiological studies were performed; an initial case-control study followed by a cohort study using an electronic questionnaire. Disease was associated with eating from the canteen salad bar on one, possibly two, specific weekdays [relative risk 4·1, 95% confidence interval (CI) 2·1–8·3]. Three separate salad bar ingredients were found to be likely sources: peeled whole carrots served in a bowl of water, grated carrots, and red peppers (in multivariate analysis, whole carrots: OR 2·1, 95% CI 1·1–4·0; grated carrots: OR 2·1, 95% CI 1·2–3·9; peppers: OR 3·3, 95% CI 1·7–6·6). We speculate that a person excreting the parasite may have contaminated the salad buffet.