Norovirus, often called the “stomach bug” or “winter vomiting disease,” is a common and highly contagious virus. It is the leading cause of acute gastroenteritis globally, responsible for millions of cases of vomiting and diarrhea each year.
Its Viral Family and Structure
Norovirus belongs to the Caliciviridae family, which causes inflammation in the stomach and intestines. It is a small, non-enveloped RNA virus, typically measuring between 27 and 38 nanometers in diameter, meaning it lacks an outer fatty membrane. This structure makes norovirus robust and resistant to various environmental conditions and many common disinfectants. Its genetic material is a single strand of RNA, encased within a protein shell called a capsid.
Why Norovirus is So Contagious
Norovirus is highly contagious due to its extremely low infectious dose; only a small number of viral particles, possibly as few as 10 to 100, can cause an infection. The virus also exhibits remarkable environmental stability, allowing it to survive on surfaces for extended periods, sometimes up to two weeks, and resisting a wide range of temperatures and pH levels.
Rapid onset of symptoms also plays a role in its quick spread. Individuals typically develop symptoms within 12 to 48 hours after exposure, and they can shed large amounts of the virus in their feces and vomit. Viral shedding can continue for an extended period, sometimes up to several weeks, even after a person’s symptoms have resolved. This prolonged shedding creates ample opportunities for widespread transmission.
How Norovirus Affects the Body
Norovirus infection typically causes acute gastroenteritis, an inflammation of the stomach and intestines. Common symptoms include sudden nausea, vomiting, watery diarrhea, and abdominal cramps. Other symptoms, such as a low-grade fever, headache, and muscle aches, may also occur. Symptoms generally last for one to three days.
The virus primarily infects the cells lining the small intestine. This infection disrupts their normal function, leading to vomiting and diarrhea. While uncomfortable, the illness is usually self-limiting in healthy individuals. However, it can lead to dehydration, particularly in young children, older adults, and those with underlying health conditions.
Understanding Its Spread and Control
Norovirus spreads primarily through the fecal-oral route, meaning the virus is transmitted when feces from an infected person are ingested by another. This can occur through direct person-to-person contact, by consuming contaminated food or water, or by touching contaminated surfaces. Aerosolized vomit from an infected person can also spread viral particles, contaminating surrounding surfaces.
Controlling norovirus outbreaks presents a challenge. Its resistance to many common disinfectants, including alcohol-based hand rubs, means that thorough handwashing with soap and water is the most effective method for removing the virus from hands. Effective environmental cleaning requires specific disinfectants proven to inactivate norovirus. Its persistence makes containment difficult, particularly in crowded settings like healthcare facilities, schools, and cruise ships.