Norovirus infection is historically known as “the Winter Vomiting Disease”. This is because the infection is usually characterized by profuse (watery) vomiting in infected individuals. Norovirus infection is a frequent cause of gastroenteritis in hospitals across the world. Norovirus infection is an all-year round occurring infection that also occurs outside the hospital environment including hotels and cruise ships. That is to say that, norovirus infection is both a community-acquired and hospital-acquired infection. The impact of norovirus infection in human population can be reduced through appropriate infection control mechanisms and timely identification of the virus causing the infection.
COMMON CAUSES OF NOROVIRUS INFECTION
Noroviruses are the causative agents of norovirus infection. Norovirus, also known as small-round-structured viruses (SRSV) or Norwalk-like viruses, belong to the Caliciviridae family of viruses. Noroviruses are the most common cause of acute gastroenteritis outbreaks all over the world. Noroviruse infections are highly infectious, and they can be transmitted from infected persons to uninfected individuals via contact with body fluids from the already infected patient. About 10-100 viral particles of noroviruses is sufficient enough to infect a person. Noroviruses can survive for a long period of time in the environment; and this can contribute to their infectiousness in human population. They are resistant to freezing, high temperatures (up to 60oC) and the levels of chlorination used in public drinking water systems. The ability of noroviruses to withstand these environmental pressures allows the organism to be highly infectious, and thus, transmissible from one person to another in a defined human population.
Noroviruses affect people of all ages, including the young and old. The commonest symptoms of norovirus infection include: nausea, vomiting and diarrhea, with fever, headache, stomach cramps and aching limbs in some cases. However, infections due to noroviruses are usually self-limiting, and most people infected with the virus usually recover within 2 days, even without any formal treatment or medical intervention. Nonetheless, noroviruses can continue to be shed in the vomitus or faeces of infected individuals for up to two weeks after the symptoms of the infection (as aforesaid) have resolved. Norovirus infection in infants, the elderly and those with some underlying diseases can give rise to severe dehydration. Therefore, it is important to include serious medical support such as rehydration when someone is infected with norovirus.
TRANSMISSION OF NOROVIRUS INFECTION
The spread of norovirus infection in human population is through the faecal-oral route. Noroviruses can also be transmitted through person-to-person contact. Contact with contaminated water or food can also spur the spread of norovirus infection. The outbreak of infection due to norovirus is common in overcrowded or contained environments such as schools, day-care centers, hospitals, college campuses, nursing homes, cruise ships, hotels and airplanes. The close proximity of people allows for the easy spread and transmission of norovirus throughout such as crowded environment. Noroviruses are common causes of foodborne infection in human population.
IDENTIFICATION OF NOROVIRUS INFECTION
The laboratory diagnosis of norovirus infection plays an important role in the proper containment of the disease or infection. Standard methods for the identification of norovirus infection include the use of electron microscopy, and PCR technique. However, these methods are not cost effective, and may be too expensive for routine testing especially in hospitals. Nowadays, there are serological techniques that can be used for the prompt and accurate detection of noroviruses from clinical samples. The Oxoid IDEIA Norovirus test is one of such serological kit or tool that can be used for the identification of noroviruses from clinical samples. The Oxoid IDEIA Norovirus test is a rapid and convenient method for the reliable detection of noroviruses directly from stool samples. And it provides sensitive and specific results within 2 hours of testing, so that any norovirus outbreak can be detected early and contained before it spreads.
TREATMENT AND PREVENTION OF NOROVIRUS INFECTION
Currently, there is no specific treatment or vaccine for norovirus infection. During an outbreak of norovirus infection, infected people are advised to always drink plenty of water in order to prevent dehydration, as a result of the excess fluid lost from the body (either via vomiting or diarrhea) of infected people. Immunity during norovirus infection does not last long, and it rarely prevents people from becoming infected again in the future. A high standard of personal and environmental hygiene especially in hospital environment and crowded areas is one of the best ways of preventing the transmission of norovirus infection. Frequent and rigorous hand washing is very important in this case to stop norovirus infection. More so, alcohol-based sanitizers and the use of soap and water for hand washing should not be replaced, but practice by all to prevent norovirus infection. Proper cleaning and disinfection of already contaminated areas in the hospital or elsewhere is important to prevent the spread of the virus. Infected people should be isolated and kept in restricted wards where they will be taken care of properly.
Patel M.M, Hall A.J, Vinje J and Parashar U.D (2009). J. Clin. Virol, 44:1-8.
CDC fact sheet. www.cdc.gov/norovirus
HPA, hospital norovirus outbreaks (England and Wales, 2010). www.hpa.org