Norovirus Structure and Classification

Norovirus are a major cause of acute gastroenteritis worldwide. Diarrheal disease is now the fourth common cause of mortality children under the age of 5 years but remain the 2nd most cause of morbidity. NoV are associated with 18% diarrheal diseases worldwide where rotavirus vaccinations has been successfully introduced. NoV has become major cause of gastroenteritis in children. NoV belong to family caliciviridae. They are non-enveloped, single stranded positive sense RNA Viruses. The genome consists of 3 Open reading frames, ORF-1 codes for non-structural protein, ORF-2 codes for major capsid protein VP1 and ORF-3 for minor capsid protein VP2. Based on sequence difference of the capsid gene (VP1), NoV have been classified in to seven genogroup GI-GVII with over 30 genotypes. Genogroups I, II, IV are associated with human infection. Despite this extensive diversity a single genotype GII.4 has been alone to be the more prevalent. Basic epidemiological disease burden data are generated from developing countries. NoV are considered fast evolving viruses and present an extensive diversity that is driven by acquisition of point mutations and recombinations. Immunity is strain or genotype specific with little or no protection conferred across genogroups. Majority of outbreaks and sporadic norovirus cases worldwide are associated with a single genotype, GII.4 which was responsible for 62% of reported NoV outbreaks in 5 continents from 2001 to 2007. GII.4 variants have been reported as major cause of global gastroenteritis pandemics starting in 1995 frequent emergence of novel GII.4 variants is known to be due to rapid evolution and antigenic variation in response to herd immunity. Novel GII.4 variants appear almost every 2 years. Recent GII.4 variant reported include Lordsdale 1996, Farmington Hills 2002, Hunter 2004, Yerseke 2006a, Den Haag 2006b, Apeldoon 2007, New Orleans 2009,most recently Sydney 2012. Detailed molecular epidemiologic investigation of NoV is associated for understanding the genetic diversity of NoV strain and emergence of novel NoV variants. However, reports have revealed that not all individuals develop symptoms and a significant proportion remains asymptomatic after NoV infections

Laboratory preparedness for SARS-CoV-2 testing in India: Harnessing a network of Virus Research & Diagnostic Laboratories

BACKGROUND & OBJECTIVES: An outbreak of respiratory illness of unknown aetiology was reported from Hubei province of Wuhan, People's Republic of China, in December 2019. The outbreak was attributed to a novel coronavirus (CoV), named as severe acute respiratory syndrome (SARS)-CoV-2 and the disease as COVID-19. Within one month, cases were reported from 25 countries. In view of the novel viral strain with reported high morbidity, establishing early countrywide diagnosis to detect imported cases became critical. Here we describe the role of a countrywide network of VRDLs in early diagnosis of COVID-19. METHODS: The Indian Council of Medical Research (ICMR)-National Institute of Virology (NIV), Pune, established screening as well as confirmatory assays for SARS-CoV-2. A total of 13 VRDLs were provided with the E gene screening real-time reverse transcription-polymerase chain reaction (rRT-PCR) assay. VRDLs were selected on the basis of their presence near an international airport/seaport and their past performance. The case definition for testing included all individuals with travel history to Wuhan and symptomatic individuals with travel history to other parts of China. This was later expanded to include symptomatic individuals returning from Singapore, Japan, Hong Kong, Thailand and South Korea. RESULTS: Within a week of standardization of the test at NIV, all VRDLs could initiate testing for SARS-CoV-2. Till February 29, 2020, a total of 2,913 samples were tested. This included both 654 individuals quarantined in the two camps and others fitting within the case definition. The quarantined individuals were tested twice - at days 0 and 14. All tested negative on both occasions. Only three individuals belonging to different districts in Kerala were found to be positive. INTERPRETATION & CONCLUSIONS: Sudden emergence of SARS-CoV-2 and its potential to cause a pandemic posed an unsurmountable challenge to the public health system of India. However, concerted efforts of various arms of the Government of India resulted in a well-coordinated action at each level. India has successfully demonstrated its ability to establish quick diagnosis of SARS-CoV-2 at NIV, Pune, and the testing VRDLs