Human astroviruses (HAstV) have been shown in several epidemiologic outpatient studies to be an important cause of viral gastroenteritis in infants and young children. HAstV have been associated with outbreaks in day-care centers for children and adults . The incidence of astrovirus infections has been estimated at between 5% and 10% in children with gastroenteritis . The reported frequency of infection by astrovirus was 8% during the winter season (from December 2000 to March 2001) in Beijing .
Astroviruses are among the most resistant viruses; they show resistance against different physical and chemical agents, they are able to maintain their infectivity at 60°C for 10 min, and they are resistant to treatment at pH 3 . Astroviruses spread via the fecal–oral route, through direct personal contact, or via contaminated food and water, and they have been reported to affect otherwise healthy people exposed to astrovirus-contaminated food or water . However, the number of reports on astrovirus detection is relatively low.
Several detection methods have been developed to detect the presence of astrovirus in clinical isolates, raw sewage samples, groundwater and surface water, including cell culture , enzyme immunoassay and nucleotide sequencing , and PCR-based assays . All of these methods are effective and accurate in detecting the virus infection in the laboratory. However, these methods have some intrinsic disadvantages such as the requirement for expensive equipment and reagents, and being laborious and time consuming, and are thus unfavorable for use on a wide scale. A detection method that is not only rapid and sensitive, but also simple and economical to handle, is needed for practical application.
To meet these requirements, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) reaction was developed as an alternative method. The LAMP assay is a rapid, accurate and cost-effective diagnostic method that amplifies the target nucleic acid under isothermal conditions, usually between 60°C and 65°C . Hence, only simple equipment such as a heating block or a water bath is required. The final products of the RT-LAMP reaction are DNA molecules with a cauliflower-like structure and multiple loops consisting of several repeats of the target sequence . LAMP has been applied for the specific detection of aquatic animal viruses such as foot-and-mouth disease virus , Singapore grouper iridovirus  and H1N1 2009 virus [10, 11].
The LAMP reaction results in large amounts of pyrophosphate ion byproduct. These ions react with Mg2+ ions to form the insoluble product, magnesium pyrophosphate. Because the Mg2+ ion concentration decreases as the LAMP reaction progresses, the LAMP reaction can be quantified by measuring the Mg2+ ion concentration in the reaction solution . Hydroxynaphthol blue (HNB) is used for colorimetric analysis of the LAMP reaction. The HNB dye-based assay has a remarkable advantage compared with other color-based assays [11, 12] in that HNB is mixed prior to amplification. The need to open the assay samples to add the dye is thereby omitted, thus reducing the risk of cross-contamination.
HAstV is classified into eight distinct antigenic serotypes, HAstV 1–8, with serotype 1 predominating in most countries . HAstV-1 was also identified as the predominant serotype in China . Wei et al.  developed a one-step, real-time reverse-transcription LAMP (rRT-LAMP) method with a turbidimeter targeting the 5’ end of the capsid gene for rapid and quantitative detection of HAstV-1 from stool specimens. In our study, RT-LAMP with HNB for specific, rapid and sensitive detection of HAstV-1 in water samples was developed. To our knowledge, this is the first report of the application of RT-LAMP with HNB to HAstV-1.