Ice cube filtering? Cooked oysters?Noro virus is hidden in the details-“PanSci TALK: Counterattack in the disk”-PanSci

This article was commissioned by the Food and Drug Administration of the Ministry of Health and Welfare, and executed by a pan-scientific plan

Text/Li Qiurong

Many people took advantage of the Mid-Autumn Festival a while ago, right? In addition to all kinds of fresh food, gastrointestinal medicine seems to be a must-have “food” for everyone. If you don’t want to have the painful experience of not being able to get out of the toilet, you must know one of the behind-the-scenes of this result-noro virus.

Department of Disease Control, Physician Zheng Haoyuan
Department of Disease Control, Physician Zheng Haoyuan

PanSci TALK on September 1, 2016: “A counterattack in the plate! Food poisoning and norovirus crisis” invited Dr. Zheng Haoyuan from the Department of Disease Control to tell us what is this highly infectious virus that once invaded Taiwan? How to prevent daily life?

There is a virus called Noro

Norovirus used to be called Norwalk-like virus (NLVs), a virus that can infect humans and cause inflammation of the gastrointestinal tract. “Fever, diarrhea, it sounds like nothing.” But the constant circulation of gastrointestinal tract inflammation, vomiting and diarrhea will cause a large amount of water loss, and even shock and death in areas where water cannot be replenished immediately.

Norovirus appears octahedral and spherical under an electron microscope. Photo/by Charles D. Humphrey, USCDCP
Norovirus appears octahedral and spherical under an electron microscope. Photo/by Charles D. Humphrey, USCDCP

Norovirus can transmit the virus through droplets (vomiting), feces and mouth, and may also be transmitted through the air (research suspected but not yet confirmed), especially if the virus attaches to the surface of an object, it will deepen and widen its infection range, and the patient will carry the virus. The longer it takes, the more likely it is to cause secondary epidemics. Taking families as an example, patients can easily spread to their caregivers; while in schools, because of group living, it is likely to cause collective infections among students.

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And different from the general impression, norovirus is particularly obvious in developed countries, and one-fifth of acute gastroenteritis incidents are caused by norovirus. It is highly infectious, long-lived, and easy to cause large-scale gatherings. It is well-deserved to say that it is the leading protagonist of food poisoning incidents.

Who should be careful?


“Do you have antibodies after getting norovirus?”

Unlike rotavirus, which can also cause diarrhea, norovirus has large genetic variability and is prone to produce multiple types of virus strains, which means that a single infection cannot produce immunity to other types of norovirus. Therefore, No matter who it is, it is possible to be infected and to be infected again. Norovirus clusters usually occur from December to February every year, and a new type of pandemic occurs every 2 to 4 years. The most troublesome thing is that no vaccine has yet been developed.

Comparison of norovirus and rotavirus.
Comparison of norovirus and rotavirus.

Can “oysters” really be eaten raw?

In addition to human-to-human transmission, contaminated drinking water and food are also the main sources of pollution. Among all possible food pollution sources, filter-feeding organisms in fresh fish and shellfish will accumulate and concentrate viruses to increase their toxicity. Take raw oysters, a frequent customer of the “raw food industry” as an example. Imported raw oysters have caused small-scale epidemics throughout Taiwan. “But we can’t check every restaurant.” Under the circumstances that the system cannot be fully monitored, Zheng Haoyuan provides One way everyone: “Don’t try raw food or a source of anxiety easily.”

Delicious oysters may become a hotbed of viruses if they are not careful. Photo/by Quinn Dombrowski@flickr
Delicious oysters may become a hotbed of viruses if they are not careful. Photo/by Quinn [email protected]

Sounds serious? “Can shellfish only bring norovirus?” Zheng Haoyuan said that it is not the only one, it may also be the vector of hepatitis A. How to eat seafood to be safe? Zheng Haoyuan suggests to everyone: “Cook a little longer.”

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In addition to specific goals like seafood, the devil is also hidden in many details of life. “Most of the ice cubes outside are made of raw water.” And many stores will use homemade ice cubes, not ice cubes from the ice factory. “Raw water can of course be drunk, but it needs proper treatment.” When faced with doubtful water sources, that is, when the water filtration system comes in handy, take the RO reverse osmosis system as an example, first use the filter to filter out the macromolecules , And then use reverse osmosis membrane to eliminate small molecules (such as viruses). “Activated carbon can only adsorb and filter bacteria, it is recommended to use RO grade water filtration system.” Zheng Haoyuan also reminded.

Norovirus may be contaminated during the ice cube manufacturing process. Photo/by Steven Depolo@flickr.
The ice cube may be contaminated with norovirus during the manufacturing process. Photo/by Steven [email protected]

“I have eaten ice cubes for decades and haven’t heard of anyone dying?” Facing the questions raised by the audience, Zheng Haoyuan said that first of all, Taiwanese people do not have the habit of drinking raw water. The source treatment of tap water is generally disinfected first, which greatly reduces To reduce the possibility of infection, the main cause of infection is that the back end of drinking water treatment is prone to cross-contamination. In addition, ice cubes often have the problem of excessively high E. coli, but because mild diarrhea is too common, most people will not regard this as a food safety problem.

After discussing so many cases and methods, what is the first step to care about food safety? “Everyone should start to care about the food put in their mouths.” Zheng Haoyuan believes that good personal hygiene is an eternal lifesaver.

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