#9 Dr.Ikegame's column
The year is nearing an end and people enjoy the Christmas season’s spirit. This swift passage of time is somewhat astonishing for me maybe because I am getting too old.
Especially this year, I spend many days alone in a condominium in Sapporo because of the business obligations. The coldness in this snowy environment makes the year-end atmosphere much severer than ever for me.
Be that as it may, we should remember that food-manufacturing industry needs to be particularly sensitive to food safety around this time of the year. As shown in Table1, number of food-poisoning incidents was greatest in August both 10 and 17 years ago. However, its number of August 2015 dramatically decreases and food-poisoning cases come about at a constant incidence all through the year. This is the trend of recent years.
As you may have guessed, cause of the change is norovirus. Food-poisoning cases caused by the virus abruptly increases in December and the momentum is maintained until March as shown in Table2. More than 10 years ago, it was widely considered that food poisoning happens in summer and food-manufacturing industry was used to strengthen their measures through May to June. In recent years, however, food-poisoning cases are caused all through the year, which seems to get rid of opportunities for food manufacturers to strengthen their hygiene activities.
As Figure1 shows, norovirus causes the most food-poisoning incidents by far among other causative substances in late years. Since its number sharply increases at the end of every year, food manufacturers should implement firmer food-safety measures at this very season.
Then what kinds of measures should we adopt? First of all, we should develop knowledge about norovirus itself. Factors affecting thermal deactivation of viruses are; temperature and time of heating, number of virus particles present in the food, and conditions surrounding the virus (dry or in a liquid, ratio of organic substances, pH, etc.). As viruses present in food are protected by such substances as protein, stricter heating-conditions are required to assure the deactivation.
In 2012, Codex Alimentarius Commission specified in its “Guidelines on the Application of General Principles of Food Hygiene to the Control of Viruses in Food” (CAC/GL 79-2012) that in order to inactivate viruses in bivalve mollus, heat treatment in which internal temperature of 85 to 90 °C for at least 90 seconds is considered to be adequate. In response to this, Sanitary Management of Large Scale Cooking Facilities Manual by Health, Labour and Welfare Ministry of Japan was revised in October 2013 to the above heat-treatment condition from previous 85 °C for 1 minute.
Apart from infection through food such as bivalve mollus, food-poisoning incidents caused by cross-contamination occur more commonly. As I mentioned in my column #5, I think measures at toilets are of central importance. In reality, however, there was a case of infection through a carpet contaminated more than 12 days ago by norovirus. Even after a period time, infectious viruses can remain in patients’ vomit and stool, and contaminated objects by them such as floors or gloves. Therefore, we need to develop measures considering various possibilities that can happen during work.
In the United States, it is reported that an average of 570-800 people die of norovirus annually, 56-71 thousands get hospitalized, 400 thousands visit emergency room, 1.7-1.9 millions visit clinic, and the total annual number of norovirus-patients is said to be 19-21 millions.
Norovirus is one of the most damaging food-poisoning causative substances in Japan too. Food manufacturers and food handlers are required to strengthen their measures against this agent.