Sapovirus Infection

12 May 2023

Causative agent

Sapovirus was first identified in an outbreak in Sapporo, Japan, in 1977. Sapovirus is a single-stranded RNA virus that belongs to the family Caliciviridae. It has been detected in shellfish and environmental water samples. Sapovirus can cause acute gastroenteritis in people of all ages, but young children have the highest burden of the disease. Gastroenteritis outbreaks due to sapovirus have been reported in various settings such as child care centres, kindergartens, nursing homes, restaurants and schools.

Clinical features

Symptoms include vomiting, diarrhoea, nausea, abdominal cramps, chills, headache, myalgia and malaise. Gastroenteritis symptoms are self-limiting and patients usually recover within a few days. A healthy person would normally recover within a few days after being infected with the virus. However, severe complications may occur in persons with chronic illnesses.

Mode of transmission

The primary mode of transmission is through the faecal-oral route. Sapovirus can be transmitted by food or water contaminated with the virus, by contact with the vomitus or faeces from infected persons or by contact with contaminated objects. Sapovirus shedding in faeces may continue for weeks after symptoms disappear.

Incubation period

The incubation period usually ranges from less than 1 day to 4 days.

Management

Adequate fluids to prevent dehydration and supportive treatment should be provided.

Prevention

No vaccine is available for sapovirus infection. As general measures to prevent gastroenteritis, members of public are advised to:

1. Maintain good personal hygiene

Perform hand hygiene frequently, especially before handling food or eating, and after using the toilet. Wash hands with liquid soap and water, and rub for at least 20 seconds; then rinse with water and dry with a disposable paper towel or hand dryer. If hand washing facilities are not available, or when hands are not visibly soiled, hand hygiene with 70 to 80% alcohol-based handrub may be considered. As alcohol does not effectively kill sapovirus, alcohol-based handrub should not substitute hand hygiene with liquid soap and water.
Wear gloves and a surgical mask while disposing of or handling vomitus and faeces, and wash hands thoroughly afterwards.
Refrain from work or attending class at school, and seek medical advice if suffering from fever, vomiting or diarrhoea.
Exclude infected persons and asymptomatic carriers from handling food and from providing care to children, the elderly and immunocompromised people.

2. Maintain good food hygiene

Adopt the 5 Keys to Food Safety in handling food, i.e. Choose (Choose safe raw materials); Clean (keep hands and utensils Clean); Separate (Separate raw and cooked food); Cook (Cook thoroughly); and Safe Temperature (keep food at Safe Temperature) to prevent foodborne diseases.
Drink only boiled water from the mains or bottled drinks from reliable sources.
Avoid drinks with ice of unknown origin.
Purchase fresh food from hygienic and reliable sources. Do not patronise illegal hawkers. In general, you can eat fruit skin after thorough washing. However, if you would like to reduce the risk of illness especially when you travel abroad, peel the fruits before eating and do not eat the peelings.
Cook all food, particularly shellfish, thoroughly before consumption.
High risk groups (e.g. pregnant women, infants, young children, the elderly and people with weakened immune systems) should avoid eating food that is to be consumed without heat treatment (e.g. raw shellfish, especially oyster) or food containing ingredients that are not cooked (e.g. pre-prepared or pre-packaged salads).

* Please visit the website of the Centre for Food Safety for more information on food safety.

3. Maintain good environmental hygiene

Maintain good indoor ventilation.
Clean vomitus/ faeces and disinfect the contaminated areas properly and immediately (please refer to the guidance on disinfection below for details). Keep other people away from the contaminated areas during cleaning.
Maintain proper function of sanitary facilities and drainage system.
Clean and disinfect toilets used by infected persons and the soiled areas.

Guidance in disinfection of area contaminated by vomitus/ faecal spillage

Keep other people away from the contaminated area during the cleaning process.
Wear gloves and a surgical mask throughout the disinfection procedure.
Discard all food if vomiting and diarrhoea occurs in an area where open food is displayed.
Remove the bulky waste cautiously from all soiled linens and clothing, soak them in 1:49 diluted household bleach (mixing 1 part of household bleach containing 5.25% sodium hypochlorite with 49 parts of water) for 30 minutes and then wash thoroughly. If immediate washing cannot be arranged, place the soiled linens and clothing inside sealed bags and wash them as soon as possible.
Use disposable towels to wipe away all the vomitus or faecal spillage from outside inward. Then apply 1:49 diluted household bleach (mixing 1 part of household bleach containing 5.25% sodium hypochlorite with 49 parts of water) to the contaminated surface and the adjacent areas liberally (e.g. disinfect areas within 2 metres from the edge of the vomitus/ faecal spillage), especially the frequently touched surfaces such as door knobs, hand rail, etc. Leave for 15 – 30 minutes to allow time for the bleach to inactivate viruses; then rinse with water and wipe the area dry.
Never use floor mops for cleaning up the vomitus.
After disinfection, soak all cleaning tools in 1:49 diluted household bleach (mixing 1 part of household bleach containing 5.25% sodium hypochlorite with 49 parts of water) for 30 minutes and then rinse thoroughly and air-dry before re-use.
Wash hands thoroughly afterwards.