Since the outbreak of the COVID-19 epidemic, people have expected that after the arrival of summer, high temperature and ultraviolet light can suppress the spread of the COVID-19 virus. However, a recent paper analyzing a case of cluster infection in a bathing center in Huai’an, Jiangsu, suggested that the spread of the COVID-19 virus has not weakened under high temperature and high humidity.
This paper was published by Academician Shen Hongbing of Nanjing Medical University, Director of Central Laboratory of Huai’an First People’s Hospital affiliated to Nanjing Medical University and others, Wang Qilong and others in JAMA Network Open, a top journal of international medical journal JAMA.
The study used the example of a clustered infection in a bathing center in Huaian City, Jiangsu Province. The researchers noted that one of the spreaders may have spread the virus to 8 other healthy individuals by bathing in a public bathing center. Eight people showed symptoms within 6 to 9 days of visiting the bathing center, one of whom was a staff member of the bathing center.
The male bath center area is about 300 square meters, the indoor temperature range is 25 ° C-41 ° C, and the humidity is about 60%. It contains a bathing pool, as well as a shower and sauna area.
“Although the temperature of the bathroom has not reached the condition for virus inactivation (56 ° C, 30 minutes), the viability of ordinary viruses should be reduced when the temperature is increased. But there is no indication that the ability of the COVID-19 virus to spread It will be weakened by the restrictions of the bathroom environment. “Wang Qilong, co-corresponding author of the paper, said in an interview with Interface News.
Wang Qilong pointed out, “Previous studies confirmed that the influenza virus and SARS virus are both warming, and the virus’s ability to spread will decrease. But in this case, different people enter the bathroom after so many days, the virus is still Can form a spread. ”
However, the research sample of this paper has certain limitations. Wang Qilong said, “We don’t know the activities of these patients in the bathroom. Whether the staff of the bath center have direct contact with these patients or have had common contact with them. It is also unclear whether the transmission route is droplet transmission, aerosol transmission, or virus. Have been living in the environment for some time. ”
Earlier, according to the “Huai’an release” news, experts from the Huai’an Health and Health Commission believed that in the above case, because the indoor air in the bathroom was not circulating and the air humidity was high, such an environment was relatively conducive to the long-term survival of the virus and was suitable for the spread of the virus. As a result of the point source outbreak, many people were infected.
Wang Qilong emphasized that this study was only an analysis of a clustered case in a specific environment. At that time, it did not want to connect the bathroom with the natural environment, but hoped that the case could play a certain role in warning, and even in areas with high temperature and humidity. Relax the epidemic prevention and control.
The similarity between the COVID-19 virus gene sequence and SARS exceeds 85%. From the point of time, the SARS epidemic 17 years ago did disappear with the arrival of summer. According to the data, SARS broke out in Guangdong Province, China in December 2002. The epidemic reached its peak in March and April 2003. By July, the number of patients and the number of suspected cases will no longer increase, and the epidemic process has basically ended.
Why do people think that the virus may disappear on its own in the summer? A professor of immunology in Beijing, who did not want to be named, told the interface news that as the sunshine duration in summer increases significantly, the ability of UV to kill viruses in the air will also increase. UV irradiation can convert oxygen into ozone, which can trap bacteria Or viral cell tissue, causing it to die.
Viral activity changes with changes in temperature and humidity, and the immune system that confronts the virus also shows different pathological characteristics with the season. The professor said that the body’s immune function will be suppressed under cold conditions, so winter and spring are often susceptible to respiratory pathogens.
“When the weather is cold, our respiratory tract is easily irritated and produces secretions, so in winter it is easy to runny nose even if you don’t catch a cold, and it is easy to produce particle droplets with coronavirus. and in summer, this This phenomenon is significantly reduced, and the transmission of droplets will also be suppressed. “The immunology professor said.
Researchers have paid close attention to the relationship between the spread of COVID-19 virus and temperature changes.
In another study, the Wang Mao team at the School of Public Health of 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. The study found that in a low-temperature environment, each time the average temperature rises by 1 ° C, the number of COVID-19 diagnoses will increase by 0.83. When the average temperature rises to 8.72 ℃, the cumulative number of diagnoses per day reaches a peak. Subsequently, the number of diagnoses per day decreased as the temperature further increased.
The “Public Prevention Guidelines for New Coronavirus Infected Pneumonia” published by the Chinese Center for Disease Control also mentioned that human coronavirus is moderately stable in a suitable maintenance solution at 4 ℃, and can be stored at -60 ℃ for several years. Increased, the virus’s resistance will decline. It is worth noting that temperature will only affect the survival time of coronavirus, not its infectivity.
Zhang Wenhong, director of the Department of Infection of Huashan Hospital Affiliated to Fudan University, once told the media that at present, it is difficult to predict whether the COVID-19 virus will disappear as the temperature rises, because it is a completely new pathogen for humans.
On March 17, Zhang Wenhong predicted the global COVID-19 epidemic, saying that most cases should be well controlled this summer, but it is not easy to say whether the outbreak will occur next winter.
Zhang Wenhong believes that COVID-19 patients will decrease after the summer, but there may be sporadic sporadic cases, which will continue to this winter and spring, and may form a small epidemic peak, and then slowly come down. It is not excluded to communicate with the opposite southern hemisphere, because there are fewer cases in the northern hemisphere in summer, but the southern hemisphere is winter, and will also transfer cases to each other, back and forth, even if it lasts for a year or two is normal. ”
The above professor of immunology also told the interface news that the COVID-19 virus may have two infection modes in winter and summer, like other human coronaviruses (such as 229e and OC43). Asymptomatic infections in summer are more common and show low intensity distribution In the state, winter may be popular again.