Abstract
Astroviruses are a known cause of human diarrhea. Recently the highly divergent astrovirus MLB1 (MLB1) was identified in a stool sample from a patient with diarrhea. It has subsequently been detected in stool from individuals with and without diarrhea. To determine whether MLB1 is associated with diarrhea, we conducted a case control study of MLB1. In parallel, the prevalence of the classic human astroviruses (HAstVs) was also determined in the same case control cohort. 400 cases and 400 paired controls from a longitudinal birth cohort in Vellore, India were analyzed by RT-PCR. While HAstVs were associated with diarrhea (p = 0.029) in this cohort, MLB1 was not; 14 of the controls and 4 cases were positive for MLB1. Furthermore, MLB1 viral load did not differ significantly between the cases and controls. The role of MLB1 in human health still remains unknown and future studies are needed.
Highlights
The first astrovirus infecting humans was described in 1975 [1]
The severity of each diarrheal episode was recorded using the 20 point Vesikari scale developed for rotaviral gastroenteritis, which includes number and duration of diarrhea and vomiting episodes, presence of fever and dehydration and classifies gastroenteritis as mild, moderate, severe and very severe [22]. 400 stool samples from acute diarrhea episodes that were negative for rotavirus by enzyme immunoassay and PCR, for norovirus by PCR, for bacterial pathogens (Vibrio cholerae, enteropathogenic Escherichia coli, Salmonella, Shigella, Aeromonas and Plesiomonas) by culture, biochemical reactions and serogrouping where appropriate and for parasites by routine saline and iodine preparations and modified acid fast stain were chosen as cases [23]
By contrast MLB1 was less likely to be present in the diarrheal samples than in the asymptomatic samples
Summary
The first astrovirus infecting humans was described in 1975 [1]. Since a total of 8 serotypes closely related to this original astrovirus (‘‘classic human astroviruses’’ (HAstVs)) have been identified, all of which are believed to cause diarrhea. Diarrhea symptoms typically last 2–4 days following a 3–4 day incubation period [2]. These infections most commonly affect children, the elderly, and the immunocompromised [3]. Since 2008, five highly divergent astroviruses have been discovered in human diarrhea specimens: MLB1 [8], astrovirus MLB2 (MLB2) [9], astrovirus VA1 (VA1) [10], astrovirus VA2 (VA2) [9], and astrovirus VA3 (VA3) [9]. Of these viruses, MLB1 has been detected at the highest frequency. It has been found in stools collected from around the world [9,11,12,13,14,15] from patients with and without diarrhea
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