The research report released by the China-WHO Joint Expert Group on the Traceability of the New Coronavirus believes that cold chain transmission is a "possible" way to introduce the new coronavirus
Many Western experts are skeptical of this judgment.
According to a report in "Nature", a virologist from the National Institute of Public Health and Environment in the Netherlands previously held a supportive view and said that frozen meat from wild animals had been linked to outbreaks of viruses such as Ebola
Regarding cold chain transmission, some foreign scholars think it is a "smoke bomb", and some support it and then withdraw it.
Why are the words of foreign experts so ambiguous? Is cold chain communication credible? Why is this approach only reported by China? At the end of August, researchers from the China Centers for Disease Control and Prevention responded to the media including Science and Technology Daily
It is found that the cold chain is spread, and the background needs to be cleared
It is found that the cold chain is spread, and the background needs to be cleared Unlike human-to-human transmission, cold chain transmission is secretive
Xu Wenbo, director of the Viral Disease Prevention and Control Institute of the Chinese Center for Disease Control and Prevention, explained that cold chain products contaminated with the new crown virus have infected employees.
Just as if footprints are intertwined on the snow, it will be difficult to discover who and which direction the first footprints to appear on the snow came from
China's discovery of cold chain transmission in Beijing, Dalian, Qingdao and other places is due to the continued tracing after the "index case".
"Background zeroing is a prerequisite for a region to be able to find cold chain transmission
The “zero case” in a region is just the “thread” of the “cold chain transmission chain”.
"The reason why China was the first to recognize the spread of the cold chain is because China has always
China's strategy of normalizing the epidemic prevention and control has made the search for clues of cold chain transmission always look like the snow that has just fallen in the first snow.
It is found that the cold chain spreads and needs to be actively monitored
It is found that the cold chain spreads and needs to be actively monitored "The traceability of cold chain transmission can only be found through active surveillance, and it requires an effective surveillance system and the cooperation of a team of scientists
If there is no effective monitoring system, even if there is cold chain transmission, it will not be noticed by scientists
Xu Wenbo cited two possible missed possibilities
.
One possibility is that the first patient with cold chain transmission is an asymptomatic infection, but because the symptoms are not serious, there is no nucleic acid test at all, and no medical treatment is just fine, then the existence of cold chain transmission will not be detected
.
(In China, at this stage, all personnel engaged in cold chain related work will undergo regular nucleic acid testing
.
)
Another possibility is that the area has not monitored the cold chain new crown pollution.
Even if there is a case of cold chain infection transmission, no one will conduct an epidemiological investigation on him, and will not ask the bottom line about where the virus of the infected person comes from.
, Will not be able to detect cold chain propagation
.
(In China, epidemiologists and laboratory experts have conducted investigations to clarify the path of infection of each infected person and the genetic relationship of the viral genome of each transmission chain and the source of infection
.
)
In fact, in many areas abroad, due to the large number of infected people, statistical research on epidemiological investigations is no longer carried out
.
Although cold chain transmission is difficult, it must be monitored
Although cold chain transmission is difficult, it must be monitored Even with local zeroing and active monitoring, cold chain transmission may not necessarily be found
.
"In the final analysis, cold chain transmission is a small probability event.
In addition, contaminated frozen items are unevenly distributed on each box and outer packaging.
It is difficult to find contaminated boxes or outer packagings with high viral loads.
The samples collected are viruses.
The load is often difficult to isolate live viruses, which makes the discovery of cold chain transmission even more difficult
.
" Xu Wenbo said
.
The more difficult thing is that in the international cold chain logistics transportation, the goods transported are often as high as several thousand tons
.
This makes the search for a small new coronavirus like finding a needle in a haystack
.
But from another aspect, once the new crown virus infects the zero case through the cold chain, the epidemic in one place will be like "a single spark can start a prairie fire
.
" Only a small number of viable viruses and one infected case can cause a large-scale epidemic
.
The low temperature environment created by the cold chain provides a good space for the virus to survive
.
Unlike pathogenic microorganisms such as parasites and bacteria, viruses will not be frozen to death.
The lower the temperature, the longer they will live.
It may even survive for decades or even hundreds of years in liquid nitrogen
.
The spread of the cold chain requires great attention
.
Ma Huilai, director of the China Field Epidemiology Training Program of the Chinese Center for Disease Control and Prevention, gave three reasons: First, the cycle is long
.
Frozen viruses are like seeds, stored for one or two years.
Once conditions are right, new epidemics may be triggered at any time
.
The second is a wide range
.
It can realize the long-distance spread of the virus across regions, countries, and even across continents
.
The third is transmission is difficult to prevent
.
Direct transmission through contact with the surface of objects involves many aspects such as cold chain processing, cold chain transportation, and product consumers, which is difficult to prevent
.
Chinese scientists believe that cold chain transmission as a means of transmission of the new crown virus must attract sufficient attention, and a global coordination mechanism should be established to collaboratively explore mechanisms to prevent cold chain pollution and transmission, and jointly explore countermeasures against long-distance transmission risks
.
Related Links
Cold chain transmission is not unique to the new coronavirus, there is an early precedent
Norovirus is often transported over long distances through trade refrigerated or frozen shellfish contaminated with the virus.
This has also led to the frequent occurrence of international clinical manifestations of norovirus infection, diarrhea and other gastrointestinal infectious diseases caused by raw seafood
.
Hepatitis A virus can also be transmitted through strawberries that are contaminated with hepatitis A virus.
If the strawberry pickers carry hepatitis A virus, the excreted virus will contaminate the strawberries.
Strawberries can be transported to consumers in close or long distances through logistics.
(Strawberries that are not cleaned) cause infection
.
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