Molecular epidemiology of caliciviruses causing outbreaks and sporadic cases of acute gastroenteritis in Spain

Abstract

The molecular epidemiology of human caliciviruses (HuCVs) causing sporadic cases and outbreaks of acute gastroenteritis around eastern Spain (Catalonia and the Valencian Community) was studied by reverse transcription-PCR (RT-PCR) and by sequencing part of the RNA polymerase gene in open reading frame 1. HuCVs were detected in 44 of 310 stool specimens (14.19%) negative for other enteric pathogens obtained from children with acute gastroenteritis. Norwalk-like viruses (NLVs) were the most common cause of the gastroenteritis outbreaks investigated here. They were detected in 14 out of 25 (56%) outbreaks with an identified pathogen. Genotypes producing both sporadic cases and outbreaks were diverse, with a predominance of GGII strains related to genotypes Melksham and Lordsdale. Five strains clustered with a "new variant" designated GGIIb, which was detected circulating throughout quite a few European countries in the years 2000 and 2001. The emergence mechanism of these strains might be the occurrence of intertypic recombinations between different viruses. The nucleotide sequence of part of the capsid gene (ORF2) from three of these strains demonstrated their relationship with Mexico virus.

FIG. 1.

Enteric viruses detected among 310 fecal specimens obtained from children under 5 years of age with acute gastroenteritis in Spain (2000 to 2001).

FIG. 2.

Phylogenetic tree of sequence data of the RNA polymerase gene (ORF1) of 27 Norwalk-like virus strains collected in Spain during 2000 to 2001 and of reference strains. Phylogenetic reconstructions were done using the minimum evolution and the maximum parsimony methods implemented in the MEGA2 program (23). Statistical confidence for the evolutionary tree was assessed by bootstrap (1,000 replicates). Reference strains are shown in boxes, and those strains isolated from gastroenteritis outbreaks are underlined. The GenBank accession numbers for the calicivirus reference strains are as follows: Lordsdale, x86557; Hawaii, HCU07611; Melksham, x81879; Hillingdon, AB 020558; Norwalk, M87661; Southampton, L07418; Desert Shield, DSU04469.