Vomiting and diarrhoea in a group of hikers visiting the Grand Canyon in the United States this summer (2024). Was it due to unsafe water or a lack of personal hygiene? Could it be both?

According to the report, dozens of people experienced a bout of vomiting and diarrhoea during a hike to see the Havasupai Falls. Some were so sick they needed helicopter retrieval. It started with a few cases but in time more than 300 people posted details of their illness on Facebook.

In a similar episode in 2022, Norovirus was identified as the probable cause of a large outbreak of vomiting and diarrhoea in the Grand Canyon National Park. In this case, the park had warned hikers of potential water safety issues prior to the outbreak. Despite this warning, more than 100 cases occurred in one outbreak and likely many more went unreported.

It is easy to understand why these events occur. I walked the Kokoda track a few years ago. It was put to us as a group that some water sources were fine while others were not OK. This didn’t make scientific sense - to me there was always someone or something above the source that could contaminate the water supply. It might be acceptable in remote high-altitude areas of Nepal but certainly not Papua New Guinea.

Bouts of vomiting and diarrhoea are commonly reported by local health departments in Australia. Many of us have been victims. It often starts with a child who brings it home from childcare. Over the next few days, the siblings, parents and grandparents all succumb.

Personal hygiene plays a key role in the prevention of transmission in this scenario, while in the case of the case of the hikers it starts with protecting a water source. Once a bug like Norovirus is introduced into a group then it can be easily transmitted to others. The hikers reported large numbers of people using limited facilities. Sanitary conditions were less than optimum.

What is Norovirus and how can we protect ourselves in the community and when travelling. It is of particular interest when cruising.

Norovirus is mainly transmitted via the faecal-oral route and is a common cause of “stomach flu” or gastroenteritis. It is characterized by vomiting and diarrhoea and usually occurs in settings with close personal interactions. These include institutional dormitories, schools, camps and hotels. It is highly contagious due to having a low infectious dose. Just one particle has a 50% chance of being transmitted. Cruising and train travel offer conditions which are suitable for person-to-person transmission. An infected toilet on a plane or train may be the source where many passengers may be exposed. Toddlers can be infected when handling toys handled by an infected child.

It is estimated that Norovirus is responsible for up to 20% of acute gastroenteritis cases globally (212,000 deaths) and is the leading cause of small children requiring medical attention in the United States. Norovirus is a leading cause of hospital visits for children in Australia.

The disease is more common during the winter months in temperate climates but can be seen at any time of the year, It only takes one infected individual to set up an outbreak.

NoroSTAT collects data on Norovirus outbreaks from participating states in the United States. According to NoroSTAT there have been almost 1,400 outbreaks from August 1, 2023, to May 2024.

Notifications for gastrointestinal disease as with respiratory tract infections were lower during the “Coronavirus Pandemic”. This could be attributed to school closures, much attention towards hand washing and other social distancing measures.

Norovirus is not a notifiable disease in Australia.

There is no vaccine for Norovirus.

Norovirus is a particular concern to travellers as it has a short incubation period of 12-48 hours and can last between 1 and 4 days in symptomatic individuals.

Some individuals are at increased risk of serious disease. These include:

• Small children
• The elderly
• Pregnancy
• Chronic disease issues
• Immune suppressed

How can we reduce the risk of Norovirus exposure while travelling? Key messages

• Clean your hands with soap and water after visiting a public toilet (alcohol is better than nothing)
• Consider returning to your cabin if you need to use a toilet when cruising
• Clean your hands with soap and water prior to eating (alcohol is better than nothing)
• Make sure your water is safe (treated or boiled)
• Choose safer foods in areas where hygiene may be a concern. Cooked shellfish would be much preferable to raw
• Peel or wash fruits
• Be very careful in situations where you know of others with vomiting and diarrhoea. Make sure you consider others if you may have already been exposed.

Review eating and drinking safely and the management of traveller’s diarrhoea. Travellers should carry appropriate medication for acute illnesses like vomiting and diarrhoea and know how to use these medications. This is very important in situations where medical services may be limited.

When are you infectious after contracting Norovirus?

You are infectious from the time you are symptomatic. The illness may last only 1-2 days, but you can pass it on for up to 2 weeks. Personal hygiene is very important to prevent transmission.

Is there a vaccine against Norovirus?

There is no vaccine to prevent norovirus infection currently (July 2024). Several vaccines are being trialled. The value proposition for a vaccine has been discussed. See Vaccine value profile for norovirus.

How long should I isolate after being diagnosed with norovirus?

It is generally accepted that you isolate for at least 48 hours after the symptoms have cleared.