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Norovirus Outbreaks (Stomach Flu)

Updated: Jul 2, 2019

Norovirus is a very contagious virus that causes vomiting and diarrhoea. The term "norovirus" was approved as the official name for this group of viruses in 2002. Previously, they were called Norwalk-like viruses, as norovirus was first identified as a virus in 1972 after an outbreak in Norwalk, Ohio.

With news of a suspected Norovirus outbreak in a Toronto school this week, I thought it would be a good idea to blog about it this week. Norovirus outbreaks are common, especially during winter.

Norovirus typically causes mild, self-limiting gastroenteritis in individuals of all ages. The virus is infectious at very low doses and is extremely stable in the environment, spreading easily from person to person. Outbreaks occur frequently in closed settings such as schools, hospitals, long-term care facilities and cruise ships. Although the virus can infect individuals of all ages, the impacts of infection tend to be greater in the elderly and individuals with underlying health conditions who are more likely to develop complications, and require hospitalisation.

How does it spread?

People can become infected with the virus in several ways:

- through direct contact with another infected person (for example, when caring for or diapering an ill child, or sharing food or utensils with an ill person)

- by touching surfaces or objects contaminated with norovirus

- by eating food or drinking water that has been contaminated

What are the symptoms?

People infected with norovirus usually develop symptoms within 24 to 48 hours, but symptoms can start as early as 12 hours after exposure. The illness often begins suddenly. The main symptoms of norovirus illness are:

- diarrhea and vomiting (children usually experience more vomiting than adults)

- nausea and stomach cramps

Other symptoms may include: low-grade fever, headache, chills, muscle aches, fatigue (a general sense of tiredness)


You can help protect yourself and others from norovirus by washing your hands thoroughly with soap and water and following other simple prevention tips as mentioned below:

1. Practice proper hand hygiene

Wash your hands thoroughly with soap and water especially after using the toilet or changing diapers, always before eating, preparing, or handling food, and before giving yourself or someone else medicine.

2. When you are sick, do not prepare food or care for others

You should not prepare food for others or provide healthcare while you are sick and for at least 2 days after symptoms stop. This also applies to sick workers in restaurants, schools, daycares, long-term care facilities, and other places where they may expose people to norovirus.

3. Clean and disinfect surfaces

You should use a chlorine bleach solution with a concentration of 1000 to 5000 ppm (5 to 25 tablespoons of household bleach [5% to 8%] per gallon of water) or other disinfectant registered as effective against norovirus by the Environmental Protection Agency (EPA).

4. Wash laundry thoroughly

Immediately remove and wash clothes or linens that may be contaminated with vomit or poop. You should:

- handle soiled items carefully without agitating them

- wear rubber or disposable gloves while handling soiled items and wash your hands after, and wash the items with detergent and hot water at the maximum available cycle length then machine dry them at the highest heat setting.


If you are infected by norovirus, make sure you drink lots of fluids to replace the fluid lost in vomitting and diarrhoea. This will help prevent dehydration. Dehydration can lead to serious problems. Severe dehydration may require hospitalisation, especially in babies and seniors. And of course, follow the above prevention guidelines to control the spread of norovirus.

It is also important to watch out for signs of dehydration in children who have norovirus illness. Children who are dehydrated may cry with few or no tears and be unusually sleepy or fussy. If you think you or someone you are caring for is severely dehydrated, call the doctor.

As always, for any questions or comments, feel free to post below.


Healthcare Consultant, in4MED


Health officials give update on virus outbreak

The author of this blog post is a Physician with over 10 years of experience working in the healthcare system as a clinician, researcher and educator. She is passionate about healthcare for older adults and strives to be a resourceful inspiration to caregivers.

*No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified healthcare professional.

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