St. Louis Encephalitis
Elizabeth Salas &
Humans and Viruses
Human Biology 115A
Date completed: 3/6/00
An article in JAMA, April 14, 1999, reported an outbreak of Norwalk-like viral Gastroenteritis in US army trainees. A Norwalk-like virus caused the outbreak and induced symptoms of vomiting, abdominal pain, diarrhea and fever. The medium range of hospitalization was from 12-72 hours. The outbreak was traced back to a food handler who fell ill in the process of baking. As a result of the outbreak, the CDC recommended more rigorous and vigilant enforcement of sanitary measures to prevent future outbreaks.
"Norwalk-Like Viral Gastroenteritis in U.S. Army Trainees -- Texas, 1998" CDC Webpage MMWR Weekly. March 26, 1999 / 48(11); 225-227
Hepatitis E virus (HEV) was recently removed from the family of Caliciviridae and is currently unclassified. It is currently unassigned genus called "Hepatitis E-like viruses". Research suggests that HEV may exist in an animal reservoir. The virus usually effects young adults and may be fatal.
Meng, Xiang-Jin, Serge Dea, Ronale E. Engle, Robert Friendship, Young S. Lyoo, Theerapol Sirinarumtir, Kitch Urairong, Dong Wang, Doris Wong, Dongwan Yoo, Yanjin Zhang, Robert H. Purcell, and Suzanne U. Emerson. "Prevalence of Antibodies to the Hepatitis E Virus in Pigs From Countries Where Hepatitis E Is Common or Is Rate in the Human Population" Journal of Medical Virology 59: 297-302 (1999)
An article, entitled "Virus-like particles of calicivirus as epitope carriers," from the Archives of Virology reports on recent research on rabbit hemorrhagic disease virus (RHDV), an animal virus of Calicivirus. The article reports the ability to insert foreign sequences in both the N- and C-terminal of VP60, one type of RHDV. As a result, scientists believe RHDV VP60 maybe used to carry foreign epitopes into the host.
Nagesha, HS, LF Wang and AD Hyatt. "Virus-Like Particles of Calicivirus as Epitope Carriers." Archives of Virology (1999) 144: 2429-2439
Research was conducted on the bovine Newbury agent-2 to classify it as a virus under Caliciviridae. Research revealed that the bovine virus was a member of Caliciviridae. It also revealed it was genetically more closely related to human SRSVs (small rounded structure viruses, also associated with Norwalk virus) than to animal caliciviruses. The research also revealed that viruses with SRSV morphology are genomically distinct from "classic" caliciviruses, which are associated with the Sapporo virus and Sapporo-like viruses.
Dastjerdi AM, Green J, Gallimore CI, Brown DW, Bridger JC. "The bovine Newbury agent-2 is genetically more closely related to human SRSVs than to animal caliciviruses." The Royal Veterinary College, University of London, London, NW1 0TU, United Kingdom Virology 1999 Feb 1; 254(1):1-5
Sixty outbreaks of Norwalk-like virus throughout the US occurring between August 1993 and July 1997 were regularly caused by the same strain defined as the 95/96 US strain. The 95/96 US strain also caused outbreaks in seven other countries on five different continents. Improvement in the surveillance of Norwalk-like virus outbreaks through the Centers for Disease Control as well as advances in technology has recently facilitated the study of Norwalk-like viruses. Research suggests the 95/96 US strain may be transmitted person-to person, in food, or aerosolized. The global spread of the virus may have occurred through international traveling, cruise ships, and importation of contaminated foods.
Noel JS, et al. Identification of a distinct common strain of "Norwalk-like viruses" having a global distribution. Journal of Infectious Disease. 1999 Jun;179(6):1334-44.
The genome of the Norwalk-like virus, Camberwell, was recently completed. The genome was more similar to the Lordsdale virus than to Norwalk which places it in the second genogroup of the Norwalk-like viruses. Camberwell and Lordsdale shared a 93.3% similarity in open reading frame 2 and 90.7% similarity in open reading frame 3.
Seah EL, et al. Open reading frame 1 of the Norwalk-like virus Camberwell: completion of sequence and expression in mammalian cells. Journal of Virology. 1999 Dec;73(12):10531-5.
Research involving circovirus and nanoviruses suggests that these plant viruses may have recombined with calicivirus in a vertebrate animal. Evidence for the suggestions comes from a replication initiator protein found in circovirus and nanovirus that strongly resembles a calicivirus. Switches between preferred host is common in viruses, however there has never been any substantial evidence to show that viruses from two different kingdoms could recombine. It has been suggested that reverse transcriptase from a retrovirus facilitated the recombination event in order for a nanovirus, which is a DNA virus, to recombine with calicivirus, which is an RNA virus.
Gibbs, MJ; Weiller, GF. "Evidence that a plant virus switched hosts to infect a vertebrate and then recombined with a vertebrate-infecting virus." Proceedings of the National Academy of Sciences of the United States of America, 1999 Jul 6, 96(14):8022-7.
Characterization of the Norwalk-like calicivirus named Arg 320 has shown that human calicivirus may be recombining. The genome of Arg 320 seemed to be a combination of two different human calicivirus. The capsid nucleotide sequences were similar to those of Snow Mountain while RNA polymerase resembles the nucleotide sequence of Lordsdale virus. Research suggests that calicivirus may recombine at a break bwtween the RNA polymerase and the capsid protein.
Jiang X, et al. "Characterization of a novel human calicivirus that may be a naturally occurring recombinant." Archives of Virology. 1999;144(12):2377-87.
Recent studies throughout the world have found human calicivirus present in various farm animals. Norwalk-like virus has been found in newborn calves as well as chicken and pigs to a lesser degree. Research suggests that certain farm animals may the reservoirs of certain human caliciviruses. As yet zoonotic transmission has not been proven nor has it been proven that particular animals are the reservoir, however further studies are underway to investigate these possibilities.
Van Der Poel WH, et al. "Norwalk-like calicivirus genes in farm animals." Emerging Infectious Disease. 2000 Jan-Feb;6(1):36-41.
Until recently, there have been few methods to detect Norwalk-like viruses in foods expected in outbreaks. Recent research has developed a method in detecting NLVs and Hepatitis A virus (HAV) in food samples. This process involves washing the food samples with "a guanidinium-phenol-based reagent, extraction with chloroform, and precipitation in isopropanol." Recovered RNA virus particles are identified with specific primers. As a result, researchers can identify the NLVs through sequence analysis in this simple and rapid method.
Schwab, KJ; Neill, FH; Fankhauser, RL; Daniels, NA; Monroe, SS; Bergmire-Sweat, DA; Estes, MK; Atmar, RL. "Development of methods to detect "Norwalk-like viruses" (NLVs) and hepatitis A virus in delicatessen foods: application to a food-borne NLV outbreak." Applied and Environmental Microbiology, 2000 Jan, 66(1):213-8. (UI: 20087540)