Molecular epidemiology of astrovirus infection in Barcelona, Spain

Abstract

A 3-year study involving 2,347 gastroenteritis samples was conducted to determine the prevalence, time distribution, and medical significance of human astrovirus infection in Barcelona, Spain. The overall incidence of astrovirus was found to be 4.9%. Mixed infections with other enteric agents were detected in 17.2% of all astrovirus-positive samples. During the 3-year period, the highest astrovirus incidence was reported in the winter months, although infections also occurred in summer. The peak detection rate was observed in children between 2 and 4 years of age. Overall, HAstV-1 was the most prevalent type, followed by HAstV-4, HAstV-3, HAstV-8, and HAstV-2. HAstV-5, HAstV-6, and HAstV-7 were not detected during these 3 years. From our serotype data for each age group, we observed that HAstV-1, HAstV-2, and HAstV-3 affected mostly children younger than 3 years of age, while HAstV-4 and HAstV-8 had a greater impact in older children. Genetic variability was analyzed between astroviruses isolated in Barcelona and strains isolated in other parts of the world. A fourth lineage was described for HAstV-1, most likely due to the large number of assayed samples, which may also explain the high level of genetic variability observed in the astrovirus isolates.

FIG. 1.

Age distribution of patients with astrovirus gastroenteritis from April 1997 to May 2000. (A) Number of astrovirus-positive samples in every age group; (B) astrovirus detection rate in every age group. In, number of samples analyzed. Age information was available for 2,309 samples.

FIG. 2.

Monthly distribution of astrovirus detected in stool specimens from May 1997 to April 2000.

FIG. 3.

Serotype distribution of astrovirus identified in every 1-year period of the study.

FIG. 4.

Serotype distribution of astrovirus infections according to age group.

FIG. 5.

Phylogenetic tree of the 348-bp region of ORF2 of 49 astrovirus isolates from Barcelona (Bcn), the 7 Oxford reference strains (HAstV-1 to HAstV-7), 2 serotype 8 strains from Mexico (Yuc-8) and the United Kingdom (HAstV-8 UK), 9 strains from Australia (Melb), 9 strains from Colombia (Col), 3 strains from the United Kingdom (Newcastle), and 1 strain from Venezuela (Ven). Bootstrap values are given at the branch points. The scale bar indicates an evolutionary distance of 0.10 nucleotide per position in the sequence. Sequences were obtained from the GenBank database with the following accession numbers: Oxford strains; L23513, L13745, L38505, L38506, U15136, L38507, and L38508; serotype 1 Newcastle strain, Z25771; serotype 8 strains, Z66541, AF260508, and AF175261; other Australian strains, AF175253, AF175254, AF175255, AF175256, AF175257, AF175258, AF175259, and AF175260; Colombian strains, AF211957, AF211958, AF211959, AF211960, AF211961, AF211962, AF211963, AF211964, and AF211965; Venezuelan strain, AF211952, AF211953, and AF211956.