The latest data shows that more than 1.1 million cases of new coronavirus pneumonia have been diagnosed globally.
As time goes by, the northern hemisphere is about to enter summer. Will the transmission capacity of the new coronavirus be weakened after the temperature rises? Will the new coronavirus pneumonia, like SARS or seasonal flu, suddenly disappear in summer?
Several experts told China Science Daily that the impact of climate on the spread of new coronaviruses cannot be ruled out, but there is little hope for controlling the epidemic by increasing temperature.
Temperature and humidity affect virus survival
Previous studies on the impact of climate on the spread of respiratory infectious diseases among people have shown that cold and dry environments can help the survival and spread of viral diseases, while warm and humid environments can weaken the spread of viruses.
The Wang Mao team of the School of Public Health at Sun Yat-sen University collected data on the number of people diagnosed daily and temperature in 429 cities and regions in China and 26 countries from January 20 to February 4.
They found that temperature is linked to virus transmission. In a low-temperature environment, for every 1 °C (33.8 ℉) increase in average temperature, the number of diagnoses per day increases by 0.83. When the average temperature rises to 8.72 °C (47.69 ℉), the cumulative number of diagnoses per day reaches a peak.
Subsequently, the number of diagnoses per day decreased as the temperature further increased.
On March 9, the paper preprint website SSRN published a paper by the University of Maryland School of Human Medicine Institute of Human Viruses and the Global Virus Network (GVN) Center of Excellence.
The article points out that the community spread of the new coronavirus pneumonia mainly spreads from east to west, and the center points are roughly distributed along the north latitude of 30-50 degrees, the average temperature is 5 °C -11 °C, and the average humidity is 47% -79%.
The timing of outbreaks in these areas coincides with the lowest point of the annual temperature cycle and the lowest temperature is below 0 °C.
Although several studies have shown that high temperature may inhibit the spread of new coronaviruses, Shen Hongbing, academician of the Chinese Academy of Engineering, and Wang Qilong, the Huai'an First Hospital affiliated to Nanjing Medical University, and others, published a study published in the Network Open of the Journal of the American Medical Association on March 30. Come to a different conclusion.
The thesis studied a case of a new coronavirus pneumonia patient with a history of contact with Wuhan in Huaian City, Jiangsu Province, which infected 8 people in the bathing center.
The results of the study show that the new coronavirus can survive under the conditions of high temperature and high humidity, and its spread has not weakened.
Prior to this, on March 19, two scholars from the Massachusetts Institute of Technology published on the preprint platform SSRN entitled "Will the coronavirus epidemic decrease in summer?"
In this study, they focused on analyzing the impact of weather on the spread of new coronaviruses.
The results show that from January to March, the total number of cases in countries with an average temperature above 18 °C and an absolute humidity above 9g/m3 is actually less than 6% of the total number of cases worldwide.
This study shows the possibility of a warm climate inhibiting the spread of the virus, but on the other hand, it also shows that the case of indigenous transmission in countries in the southern hemisphere may mean that the new coronavirus is more sensitive to higher temperatures than the past influenza and other respiratory viruses For tolerance.
"It can be seen from the existing scientific literature and news reports that the suitable temperature and range for the survival of the new coronavirus is relatively wide, and it has a strong adaptability to the environment. Relatively high and low temperatures may be infectious.
Whether there is a new coronavirus pneumonia in extreme low temperature environment requires urgent research evidence. Qi Xin, an associate professor in the Department of Epidemiology and Health Statistics, School of Public Health, Xi'an Jiaotong University, said.
Temperature is not a decisive factor
The epidemic situation of the new coronavirus pneumonia is raging around the world, but people's understanding of this new virus is still limited.
At present, the presumption of the relationship between the new coronavirus and the temperature is not only based on the diagnosed cases and climate data, but also based on the knowledge and experience of other coronaviruses.
The “Prevention Guide for Public Protection of New Coronavirus Infected Pneumonia” compiled by the Chinese Center for Disease Control stated that human coronavirus is more sensitive to heat. The virus is suitable to maintain medium stability in droplets at 4 °C, but as the temperature increases, the virus Resistance decreased.
Previously, the World Health Organization believed that there are three factors for controlling and eliminating SARS: transparent and public case notifications, effective isolation measures for patients in various countries, and warming weather.
In an interview organized by the China Association for Science and Technology, Shu Yuelong, Dean of the School of Public Health (Shenzhen), Sun Yat-sen University pointed out that when the SARS epidemic occurred in the year, the world, especially China, also adopted strong prevention and control measures, including the rapid detection of cases for isolation, tracking each Cases of close-knit crowds carried out prevention and control measures such as isolation and medical observation, and finally successfully prevented and controlled the epidemic.
He emphasized that the increase in temperature in summer may reduce the epidemic intensity, but it is unlikely to disappear naturally.
At the recently held "Global Anti-epidemic, Concentric Four Seas" Second New Coronavirus Pneumonia Multidisciplinary Forum, Jin Dongyan, an academician of the American Academy of Microbiology and a virologist at the University of Hong Kong, pointed out that human coronavirus infection has a certain seasonality, and new coronavirus Whether it is seasonal or not is not known, but it is possible.
"From the point of view of the outbreak area, Wuhan, China and Daegu, South Korea, are relatively cold and dry. There is no community outbreak in places with relatively high temperatures and humidities like Malaysia and Singapore. Is it regular and requires epidemiology? Experts do some research to understand whether the new coronavirus is related to temperature and humidity. "Jin Dongyan said.
A virologist also expressed the same view: "From a local perspective, the new coronavirus will be affected by climate conditions such as temperature and humidity; from the perspective of global prevention and control, the impact is not large, because the temperature in the northern hemisphere is high, and the temperature in the southern hemisphere is low. At present, the world is in a pandemic state. I hope there is little hope to control the epidemic by increasing the temperature. "
The above-mentioned virologists said that temperature and humidity will have a greater impact on the new coronavirus. But now there is no strict experimental data support, and there is no rigorous conclusion about how much influence it can play or not.
Instead of relying on "weather", it is better to rely on yourself
Michael Ryan, executive director of the World Health Organization's Health Emergency Program, once pointed out that it is necessary to assume that the new coronavirus still has the ability to spread in the summer. To this end, countries must step up their actions and cannot expect the new coronavirus to disappear on its own like the influenza virus in the summer.
At present, the number of confirmed cases in tropical countries such as Singapore, Malaysia, and Brazil is rising. Qi Xin said that under the current circumstances, only strict prevention and control can reduce the spread of the virus.
"If you want to explore the correlation between viruses and climate, not only climatic and meteorological conditions, but also the impact of policy measures must be considered in the research process. This is a relatively complex system engineering, and the climate impact only accounts for part of it." Qi Xin said.
The paper published by the Mauricio Santillana research group of Boston Children's Hospital on the preprint website medRxiv also shows this: if extensive public health interventions are not implemented, weather changes alone (such as increases in spring and summer temperatures and humidity in the northern hemisphere) may not Will reduce the spread of new coronavirus.
Therefore, in order to prevent the spread of new coronaviruses on a global scale, more reliance on strong prevention and control measures should not be allowed to relax due to rising temperatures.
"The impact of climate change on people's health has significant regional characteristics. In developing countries such as South Asia and Africa, people's ability to cope with the impact of climate change on economic society and health is relatively weak. "Qi Xin emphasized.
The new coronavirus pneumonia has raged around the world and the international community Attention should be paid to the possible pandemic in developing countries, and whether the correlation between the spread of new coronavirus and climate in these countries is more significant, Qi Xin said.
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