Superspreader event provides clues for suppression of coronavirus

Some scientists, looking for ways to prevent the exponential growth of coronavirus infections after the lockdown is lifted, are focusing on new approaches.

© AP communication
FILE-Files on Tuesday, February 25, 2020 Bourbon Street in File Photo is the Sea of ​​Mankind on Mardi Gras Day in New Orleans. In the city here, the old saying “let’s have a good time” has changed to the new local saying, “wash your hands.” A month ago, the city was crowded with people and immersed in the annual communal delight of Mardi Gras. But now New Orleans has joined these places to close the bar, eliminating meals in restaurants and banning the crowd. (AP Photo / Rusty Costanza, file)

The theory is that if hundreds of participants ban other measures such as large events or wearing face masks that could infect themselves in hours of space, the new coronavirus’s rate of progression would increase. It will be late and shops and factories will restart.

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The explosive growth of coronavirus infections that overwhelmed hospitals in some countries was largely caused by British horse racing earlier this year, carnival celebrations in the United States and Germany, or football matches in Italy, the researchers said. Is thinking

Research on super-diffusion events will help scientists better understand how viruses spread in crowded situations such as offices, schools, churches, gyms, public transport, weddings, trade conferences, sports games, etc. Help guide the government in regulating public places.

There is little doubt about the mechanisms involved in event superdiffusion. A study published last week by the American Academy of Sciences in the United States shows that a minute of loud speech is enough to produce thousands of droplets that stay in the air for about 12 minutes, with the potential to infect anyone in the area. I found that there is. In a similar study, aerosols containing viruses, which are smaller particles than droplets, can float for hours after being released into an indoor space.

A more surprising finding is that outbreaks tend to be more severe than infections that occur in other situations, probably due to persistent exposure to large amounts of the virus.

“Most of the cases worldwide, especially most deaths, occurred after a hyperdiffusion event,” said Hendrik Streck, a virologist at the Bonn University Hospital in Germany, who published the world’s first study of a new coronavirus superdiffusion event. It was

His study of an outbreak in the western county of Heinsberg, which became the epicenter of the German epidemic in March, showed that the infection spread like a wildfire to the entire region after about 400 people attended a traditional carnival party. Established that. On February 15th, I drank, sang, kissed and danced for several hours in the big hall.

Dr. Streeck said the people who attended were not only infected, and later spread the virus throughout the county, but also had more severe symptoms and a relatively serious illness. A few weeks later, thousands were infected and dozens died throughout the region.

Although there are hyperspread events in many infectious diseases, Covid-19 is particularly dangerous because the virus has a long incubation period and can cause others to be asymptomatic and infect others. Thurs and MERS are the other two deadly coronaviruses that have caused global outbreaks in recent years, and were also triggered by superdiffusion events, studies show.

A celebration of Mardi Gras, Louisiana, practice of choirs in Skagit County, Washington, and a meeting of executives at the Biogen pharmaceutical company near Boston helped scientists give a fatal boost to the pandemic, a one-time event Is one of.

According to an analysis of the Environmental Working Group, hundreds of infected meat packing factories in the United States have also emerged as super-spread areas. Nearly twice the national average of Covid-19 cases has been found in counties with or near meatpacking plants. , A non-profit organization.

In April, Brain County, Idaho, became one of America’s coronavirus hotspots when hundreds of people tested positive after an apreskey party. Smaller events such as weddings, parties and funerals have also helped to spread the epidemic. In one case, the infected individual visited a funeral and birthday party within three days of February, when the virus spread to 16 people, three of whom died.

“It’s pretty clear now that it’s a great opportunity for many people nearby to spread the virus,” said Mark Lipsic, professor of epidemiology at Harvard University. Chang Public Health School.

Experiences from several European countries seem to confirm the special role that superdiffusion events play. In the last four weeks, Germany, Austria, Denmark, Norway, and other countries with early withdrawals from Lockdown have removed most of their restrictions on public life, except those targeted at mass gatherings. So far, new infection rates are low and constant. Sweden, which had never had a mandatory blockade, managed to curb and reduce proliferation by relying on only one restrictive measure to ban rallying more than 50 people.

The remaining one question mark is about school. Although no rapid increase in infectious diseases has been reported in countries where schools have reopened, some scientists fear the school will act as a pandemic accelerator.

According to the professor, Sars, another coronavirus that occurs in China and is almost genetically identical to Covid-19, was temporarily released in 2003 after a foreigner staying at the Metropole Hotel in Hong Kong infected guests. Spread all over the world. Michael Small, Lecturer of Applied Mathematics at the University of Western Australia.

Professor Small, who chairs Complex Engineering Systems at CSIRO, the country’s national scientific institution, said both coronavirus outbreaks were investigated and, as a lesson, authorities need to curb all groups of more than 100 people. I am.

“This may be the end of an open plan office,” he said. “We can clearly see that from data from many places. Superdiffusion events cause bursts of infections and drive exponential growth, but if you limit the population of people, it’s very quick. It can be reduced to linear growth. “

According to his modeling, the economic impact is much less, including banning a large number of events, asking a significant number of white-collar workers to work from home and encouraging the widespread use of smartphone contact tracking apps. You can replace the lockdown with targeted measures.

How about a crowded subway or commuter train? Professor Small is convinced that the use of the subway during rush hours will certainly be a super-popular event.

Stanford University lecturer and Nobel laureate Professor Michael Levitt has said that the London authorities reduced the number of subways in March and caused more congestion than normal, causing a super-popular situation. He advocates the use of face masks and regular testing of bus drivers, shopkeepers and courier delivery. He said the bar should also be regulated, as loud music forces regulars to speak out loud.

In the UK, where Covid-19 has the worst mortality rate in the world, authorities allowed a series of large-scale concerts, soccer games, horse racing, and other large-scale events in March. George Batchelor, director of data analytics firm Edge Health, which works with UK healthcare providers, believes that these groups have caused significant increases in hospitalization and Covid-19-related mortality in their respective regions. He studied two soccer games and horse racing. All this was done outdoors, followed by heavy use of public transport and visits to bars and pubs.

“It doesn’t seem very wise to allow such an event right away,” said Bachelor.

Some of the lessons learned have already been applied. In Germany, choirs are banned from religious services and Bundesliga football games are played without spectators, while British churches are considering a ticket system to avoid congestion.

According to an Austrian spokesman, Austria will be allowed cultural events such as concerts with up to 1,000 visitors from August under strict security measures, but clubs and nightspots will remain closed .. A study published this week found that the ban on large-scale rallying was the biggest contributor to controlling the epidemic in Germany.

Professor Christopher Moore, a physicist at the Santa Fe Institute, said hyperextensive events could even rekindle the epidemic if the situation appeared to be under control.

Dr. Streak, a German virologist, agrees. While most experts anticipate a deadly second wave of coronavirus infections in the fall, he will focus more on preventing superdiffusion events and alert surveillance to avoid such scenarios. Hope it helps.

“We are all doing experiments in our country. No one knows how to do this right,” he said.

Contact Bojan Pancevski at [email protected]