Chapter 3Infectious Diseases Related To Travel
Aron J. Hall, Ben Lopman
Norovirus infection is caused by nonenveloped, single-stranded RNA viruses of the genus Norovirus, which have also been referred to as “Norwalk-like viruses,” Norwalk viruses, human caliciviruses, and small round-structured viruses.
MODE OF TRANSMISSION
Transmission occurs primarily through the fecal-oral route, either through direct person-to-person contact or indirectly via contaminated food or water. Norovirus is also indirectly spread through aerosols of vomitus and contaminated environmental surfaces and objects.
Seroprevalence studies in the Amazon, southern Africa, Mexico, Chile, and Canada have shown that norovirus infections are common throughout the world, and most children will have experienced at least 1 infection by the age of 5 years. Norovirus infections can occur year round; in temperate climates, norovirus activity peaks during the winter. In the United States, norovirus is the leading cause of sporadic cases and outbreaks of gastroenteritis, estimated to cause 23 million illnesses a year and up to 50% of all foodborne outbreaks. In both developing and developed countries, noroviruses are estimated to cause 12% of all severe diarrheal disease.
Norovirus appears to be increasing as a cause of travelers’ diarrhea; rates range from 3% to 17% of returning travelers. However, coinfection and asymptomatic infection with norovirus is common, so focused studies are needed to determine exactly how frequently norovirus is the cause of disease. Risk for infection is present anywhere food is prepared in an unsanitary manner and may become contaminated, or where drinking water is inadequately treated. Of particular risk are “ready-to-eat” cold foods, such as sandwiches and salads. Raw shellfish, especially oysters, are also a frequent source of infection, because virus from contaminated water concentrates in the gut of these filter feeders. Contaminated ice has also been previously implicated in outbreaks.
Large norovirus outbreaks are associated with settings where people live in close quarters and can easily infect each other, such as hotels, cruise ships, and camps. Viral contamination of inanimate objects may persist during outbreaks and be a source of infection. On cruise ships, for instance, such environmental contamination has caused recurrent norovirus outbreaks on successive cruises with newly boarded passengers. Transmission of norovirus on airplanes has been reported during both domestic and international flights, and likely results from contamination of lavatories or from symptomatic passengers in the cabin.
Infected people usually have an acute onset of violent vomiting with nonbloody diarrhea. The incubation period is 24–48 hours. Other symptoms include abdominal cramps, nausea, and occasionally a low-grade fever. Illness is generally self-limited, and full recovery can be expected in 1–4 days. In some cases, dehydration, especially in patients who are very young or elderly, may require medical attention.
Norovirus infection is generally diagnosed by symptoms. No laboratory tests have been approved by the Food and Drug Administration to guide clinical management, but laboratory testing is used during outbreak investigations by public health agencies. Norovirus diagnostic testing is usually not available in developing countries.
The most common diagnostic test used at state public health laboratories and CDC is RT-PCR, which rapidly and reliably detects the virus in stool specimens. Several commercial EIAs are available to detect the virus in stool specimens. The specificity and sensitivity of these assays are poor compared with RT-PCR.
These tests have been used occasionally by cruise lines during outbreaks on ships.
The mainstay of management is supportive care, such as rest and oral or intravenous rehydration.
PREVENTIVE MEASURES FOR TRAVELERS
No vaccines are available. Noroviruses are common and highly contagious, but the risk for infection can be minimized by frequent and proper handwashing and avoiding possibly contaminated food and water.
In addition to handwashing, measures to prevent transmission of noroviruses between people traveling together include carefully cleaning up fecal material or vomit and disinfecting contaminated surfaces and toilet areas. Products should be approved by the Environmental Protection Agency for norovirus disinfection; alternatively, a high concentration of domestic bleach (at least a 1:50 solution of bleach and water) may be used. Soiled articles of clothing should be washed and machine-dried at high heat.
To help prevent the spread of noroviruses, ill people have been confined on cruise ships and in institutional settings.
- Glass RI, Parashar UD, Estes MK. Norovirus gastroenteritis. N Engl J Med. 2009 Oct 29;361(18):1776–85.
- Kirking HL, Cortes J, Burrer S, Hall AJ, Cohen NJ, Lipman H, et al. Likely transmission of norovirus on an airplane, October 2008. Clin Infect Dis. 2010 May 1;50(9):1216–21.
- Koo HL, Ajami NJ, Jiang ZD, Neill FH, Atmar RL, Ericsson CD, et al. Noroviruses as a cause of diarrhea in travelers to Guatemala, India, and Mexico. J Clin Microbiol. 2010 May;48(5):1673–6.
- Kornylo K, Kim DK, Widdowson MA, Turabelidze G, Averhoff FM. Risk of norovirus transmission during air travel. J Travel Med. 2009 Sep–Oct;16(5):349–51.
- Mead PS, Slutsker L, Dietz V, McCaig LF, Bresee JS, Shapiro C, et al. Food-related illness and death in the United States. Emerg Infect Dis. 1999 Sep–Oct;5(5):607–25.
- Parashar U, Quiroz ES, Mounts AW, Monroe SS, Fankhauser RL, Ando T, et al. “Norwalk-like viruses.” Public health consequences and outbreak management. MMWR Recomm Rep. 2001 Jun 1;50 (RR-9):1–17.
- Patel MM, Widdowson MA, Glass RI, Akazawa K, Vinje J, Parashar UD. Systematic literature review of role of noroviruses in sporadic gastroenteritis. Emerg Infect Dis. 2008 Aug;14(8):1224–31.
- Widdowson MA, Cramer EH, Hadley L, Bresee JS, Beard RS, Bulens SN, et al. Outbreaks of acute gastroenteritis on cruise ships and on land: identification of a predominant circulating strain of norovirus—United States, 2002. J Infect Dis. 2004 Jul 1;190(1):27–36.
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