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About infectious gastroenteritis (norovirus)

Reports of outbreaks in nursery school, elementary school, elderly person facility increase.
In each family, please note appropriate processing of hand-washing, flight and vomiting thing, enough heating of food.

About infectious gastroenteritis (norovirus)

 Infectious gastroenteritis due to norovirus is infectious disease to be a lot prevalent in winter mainly, but outbreak is seen throughout the year.
 We understand characteristic of norovirus, and let's prevent infection due to norovirus.

With infectious gastroenteritis

 Infectious gastroenteritis is generic name of infection to cause gastroenteritis symptoms such as diarrhea, vomiting with bacteria, virus.
 Most of causative pathogens are norovirus.
 In addition, there are rotavirus, sapovirus, adenovirus.

The outbreak situation of infectious gastroenteritis in Yokohama-shi

 In Yokohama-shi, we receive outbreak report of infectious gastroenteritis from "fixed point medical institution" of 94 places of cities every week.
 In addition, in average year, outbreaks occur frequently at infants facility (nursery school, kindergarten), school, elderly person facility, hospital.
 When we warn not to be usually infected at such a place living a group life, and infected person is confirmed in facility, correspondence for prevention of prompt infection spread is necessary.
<< reference >>  Infectious gastroenteritis city outbreak trend fixed point information (Yokohama City Inst. of Health homepage)

With norovirus

 Acute gastroenteritis is caused to person of every age, and norovirus is strong virus of infection so that viral load is infected with less than 100 minimal quantity.
 It occurs throughout the year, but is prevalent in winter (mainly from November to February) in particular.
 Symptoms such as diarrhea, vomiting, fever are almost seen after latency period of 1-2 days when infected with norovirus.
 We recover from the onset in 1-2 days, but it is aggravated, and attention is usually necessary for infants and elderly person who are poor at resistance as we may let the trachea clog up with vomitus.
<< reference >> Q&A (Ministry of Health, Labour and Welfare homepage) about norovirus

Main infection course of norovirus

 Norovirus is transmitted by entering at entrance.
 We greatly divide into infection, and there are three next routes.
 Particularly, secondary infection with infectious disease route occurs a lot 1.

1.<< infectious disease route >>
When finger has norovirus when we treat vomiting things of infected person and we enter mouth through finger and infect or when we breathe in norovirus which dries, and floated and infect 
2.<< food poisoning route >>
When infected person adds norovirus to food at the time of cooking, and we eat the food, and different person is infected
3.<< food poisoning route >>
When we eat without heating bivalves which accumulated norovirus live or enough and are infected 

Point of the infection prevention

 The most effective infection precaution is hand-washing. After the front and restroom of cooking, let's wash hand well. In addition, we always take enough sleep and nutrition, and let's keep physical condition well.
 Infection power of norovirus is lost in heating more than 85 degrees Celsius one minute. Food in particular will heat up at central temperature 85-90 degrees Celsius more than 90 seconds.
 Infection preventive measures against hand-washing are necessary to have possibilities to continue exhausting virus after the recovery for around one month when we are infected with norovirus if long for one week. 

Point of hand-washing

  • Before the front and meal of cooking, let's wash under soap and running water well enough after restroom in the next of sanitation.
  • We trim nail close. We take off ring or clock before hand-washing.
  • We beat soap enough and wash finger using nailbrush.
  • We perform rinse under running water enough.
  • We wipe with clean towel or paper towel. We stop common use of towel.

<< reference >> "Method of hand-washing" (PDF)

Point of disposal of filth (vomiting thing, ordure)

 A large quantity of norovirus is included in vomiting thing, ordure of infected person.
 In addition, when norovirus dries, we drift in the air and this is in mouth and may infect.
 Therefore, vomiting things process immediately, and please ventilate after the processing during processing enough.

  • Let's employ disposable gloves without touching to vomiting things barehanded.
  • At the time of processing, let's be careful not to pollute clothes with vomiting things using disposable mask.
  • (we include paper which we used for wiping off) can enter plastic bag and seals up vomiting things well, and let's dispose immediately.
  • (we put disinfector to sterilize vomiting things in plastic bag before sealing up.)
  • After the processing, let's wash hand well by all means.

Point of disinfection

 Let's use chlorine-based bleach (ingredient: sodium hypochlorite) for disinfection of norovirus by all means.
 (※ attention! Alcohol and reverse soap are not effective.)

  • We wipe off to dip and do doorknobs of restroom and disinfection of kitchen utensil using liquid of 0.02% of density (200 ppm).
  • Dirty floors or vomiting thing wipe off to dip using liquid of more highly-concentrated 0.1% (1,000 ppm), and they do disinfection of own body in vomiting things.
  • In the case of thing which chlorine-based bleach including discoloring clothing cannot use, we sterilize with steam (in 85 degrees Celsius or more more than one minute) such as boiling water or steam iron after the lower washing well. As norovirus is left in washrooms which did lower washing, let's sterilize there properly.

<< reference >> "Disposal of vomiting things, disinfection method" (PDF)

<< reference >> ★"(precautions) with sodium hypochlorite"

  • Please keep undiluted solution in place where shading is possible to keep disinfection effect.
  • As antiseptic solution which we diluted loses disinfection effect with time, please make cooking ahead in disinfection without doing each time.
  • As you may corrode metal materials, you wash with water after the disinfection immediately, or you wipe off, and please do.
  • It may discolor when we use for clothes or carpet.
  • When we use, let's do enough ventilation. Chlorine gas may appear when you mix, and please do not use together with acid detergents as you are dangerous.
  • Because skin rough weather is caused, it is not usable in disinfection such as fingers.

Point (the prevention of food poisoning) at the time of cooking

 When person who was already infected does cooking of meal, we touch norovirus for food, and attention is necessary as person who ate it may infect.

  • When we perform health care from day and have symptoms such as diarrhea or vomiting, work to handle food directly, please wait.
  • Food needing food and heating that may be polluted by virus will heat up at central temperature 85-90 degrees Celsius more than 90 seconds.
  • As for cutting board and kitchen knife, tableware, the dishcloth, heating of one minute is effective in boiling water (more than 85 degrees Celsius).

If we are infected with norovirus

 This virus does not have effective antiviral agent and vaccine. Symptomatic treatment is usually provided.
 Let's perform supply of moisture and nutrition enough that dehydration is caused and is not worn out while diarrhea or vomiting continue. Weak infants and elderly person of resistance in particular require attention.
 When symptom is severe, please consult medical institution early.

We prevent secondary infection in the families

 When there is person with symptom to you and family, let's be careful not to be infected secondarily.


  • Let's carry out processing, sterilization such as prompt vomiting things.
  • Let's wash hand diligently.
  • Place to touch by hand including doorknob of restroom will sterilize properly.
  • We exchange water of bath every day, and let's clean floor, washbowl, chair of bathtub and bath cleanly.
  • Person having diarrhea will take a bath last.
  • Let's stop common use of towel and bath towel.

Prevention of food poisoning

 When person cooking food is infected, we add norovirus to food, and person who ate it may be poisoned by food.
 Therefore, one that we eat and assist in cooking worker, facility performs health care from on day, and person with poor physical condition such as diarrhea will write down work engagement.


  • City of Yokohama, Health and Social Welfare Bureau health security section TEL 045-671-2463 FAX 045-664-7296
  • City of Yokohama, Health and Social Welfare Bureau food board of health TEL 045-671-2460 FAX 045-641-6074

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