Disease in Focus: Norovirus

Brace yourself, the winter vomiting bug is coming.

Today, our Disease in Focus is Norovirus, a highly contagious virus that can cause diarrhea, vomiting, nausea, fever and body aches. Also known as the winter vomiting bug, or the stomach bug, it is caused by Noroviruses belonging to the Caliciviridae family. It is the most common cause of viral gastroentiritis in humans and can affect people of all ages. Currently, a norovirus outbreak is sweeping UK hospitals forcing authorities to close wards and restrict visiting hours.

A World Health Organization (WHO) study revealed that Norovirus was the leading cause of foodborne illness causing 125 million global cases in 2010. Among diarrheal diseases, norovirus was responsible for 684 million cases and killing more than 212,000 in 2010.

It was originally named "Norwalk agent" after Norwalk, Ohio where the first confirmed outbreak occured in 1968. It was first identified in 1972 from human stool sample using electron microscopy and was named "Norwalk virus".

_{norovirus particles in feces, By Graham Beards, Wikipedia}

Other strains and serotypes of norovirus includes Norwalk virus, Hawaii virus, Snow mountain virus, Mexico virus, Desert Shield virus, Southampton virus, Lordsdale virus, and Wilkinson virus.

Symptoms and Transmissions

Norovirus infection is the leading cause of acute gastroenteritis, or the inflammation of the gastrointestinal tract that involves the stomach and the small intestine. Patients will develop symptoms 12 to 48 hours after exposure from norovirus. Common symptoms include diarrhea, vomiting, nausea, and stomach pain and may have accompanying fever, headache, and other body aches. While these symptoms can be very unpleasant, severe complications are very rare and most patients will recover after 2 to 3 days. It is worth noting that patients, due to diarrhea and vomiting can suffer from dehydration and may require medical attention. Norovirus causes 300 deaths annually in the US on people who are mostly children, elderlies, and those with compromised immune system.

The norovirus is highly contagious and can be transmitted by intake of fecally contaminated food and water, contact with infected person, and contact with contaminated objects. The virus can survive in hot or cold environment and may spread through the air from vomits and contaminated objects. Because of this, outbreaks can occur in closed and crowded environments such as hospitals, nursing homes, child care centers, schools and cruise ships.

It is so contagious that medical professionals advise people to stay at home especially during suspected outbreaks to prevent it from spreading. Patients who experienced diarrhea and vomiting are even asked to stay away from hospitals to prevent an epidemic.

Diagnosis and Treatment

Usually, diagnosis can be based on patient's symptoms but because these symptoms are similar with other viral diarrheas like rotavirus, laboratory tests is recommended for confirmation. Laboratory tests such as RT-qPCR assays is the preferred method for detecting the virus. Specimens such as stool, vomit, and serum can be collected from patients as well as food, water, and other environmental specimens.

Since norovirus is viral and not bacterial, it can not be cured by antibiotics. Also, there is no specific medicine against it but healthy people usually manage to recover after few days. Patients are advised to drink plenty of fluids to avoid dehydration. Children may be given oral rehydration solutions to replace lost fluids and other minerals. Paracetamol is also given for fever or body pains. Patients are advised to take plenty of rest and let the virus run its course.

Prevention

The norovirus can survive outside a human host for long period of time. It can survive for weeks on hard surface, up to 12 days on contaminated fabrics and months or even years in still water. Cutting the risk of acquiring the virus will have a lot to do with good and proper hygiene.

Proper handwashing will greatly prevent the virus from infecting our body. Rinsing food and vegetables, and preparing our food properly also help. The virus can live at 140°F so it's best to cook our food, particularly shellfish like oysters thoroughly.

_{screengrabbed from CDC}

It is also best to disinfect our environment by cleaning contaminated surfaces with bleach or any disenfectant proven effective against norovirus. Contaminated disposable items like diapers should be thrown away carefully. Suspected contaminated clothings, and beddings should be washed separately. People who had norovirus are advised not to prepare food or provide healthcare to other people while sick and for at least 2 days after symptoms stop.

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Previously on Disease in Focus:
Sepsis
Gonorrhea

_{Disclaimer: Disease in Focus is written to provide information but should not be used as basis for diagnosis and treatment. If you have symptoms of any disease discussed here, please seek advice from medical professionals.}

_{Sources: Wikipedia | CDC | WebMD | NCBI | Mayo Clinic}

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