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‘Outdoor impact’ gives South a break from spring Covid-19 surge

Six months after the drive to vaccinate the US population from Covid-19, the gap between the states with the highest and lowest vaccination rates has widened. but until now The slower vaccination states have yet to pay large sums for new case outbreaks. This is in part thanks to what scientists call outdoor effects.

Many of the least populous states to receive at least one vaccination are located in the Deep South. including Mississippi, Georgia, Alabama and Arkansas, and avoided the pandemic last spring. Just to see the increase in cases in the summer months . Most of these states also avoided the sharp increase in cases in the first few months of this year. Even many northeastern states, such as Vermont, Massachusetts, and New Hampshire, which now has the highest vaccination rates in the United States. There was an increase in the number of patients during winter and early spring

Residents of most southern states face a reduced risk of winter and spring transmission. This is because they can spend more time socializing in open spaces where the virus can spread more easily. According to epidemiologists and research reports And they don̵

7;t need a heating system that dries the indoor air. Dozens of studies show that the SARS-CoV-2 virus spreads more easily outdoors and in more humid environments.

However, doctors and health officials worry that As summer approaches Warm-weather states with low vaccination rates May be at risk of a new round of COVID-19 pandemic as heat causes people to spend more time in dry and air-conditioned places

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Marty Makary, a cancer surgeon and epidemiologist at Johns Hopkins University, said in an interview: “These are outdoor societies. And the impact of the outdoors is far greater than the public appreciation. “Winds, seasons, and outdoor culture may be the main contributors to the decline in case numbers.”

In the 10 states with the lowest vaccination rates Seven were in the Deep South—37.9% of people on average received at least one vaccine, compared to 50.5% of the total U.S. population who received at least one. According to a Wall Street Journal analysis of U.S. Centers for Disease Control and Prevention data, of the 10 states most vaccinated. The average initial dosing rate was 62.6%.

New confirmed cases continued to decline from late February to late May in these southern states. In Mississippi, where only 34% of the population has received at least one dose of the vaccine. This makes it the least vaccinated state in the country. The seven-day average of new cases dropped about 72% from March 1 to 162 per day, deviating only slightly from the consistent downtrend. The average daily number of cases has declined by about 83% in Georgia, 81% in Arkansas and 51% in Louisiana since March 1, where the trend has continued to decline, although all three states have had vaccination rates. First time below 40%

indoor dining Exercise classes, concerts, these commonplace events are returning to everyday life. But due to COVID-19 So everyone has a different level of comfort. What happens in the brain when we decide whether something is risky or not? Illustration: Laura Kammermann

Of the 10 states with the highest vaccination rates in the country which, besides Hawaii and New Mexico, is all in the northeast. There were nine spring outbreaks, or a continued increase in the likelihood of new infections during the same period. before high vaccination rates start knocking them down.

in Vermont It is currently the country’s most vaccinated state, with 70.2% of residents receiving at least partial vaccination. The 7-day moving average of patients nearly doubled between March 1 and April 4 to nearly 190 times a day, the highest level in 2021. Since then, an average of 27.3 new cases per day has been reported in the state. Maine, Massachusetts and New Hampshire Found that the number of cases skyrocketed in late March and early April. before falling about 32%, 83% and 76% respectively compared to March 1 levels.

The disparity underscores the idea that the amount of time people spend outside—and spend a little time in low-humidity indoor environments breathing extremely hot or cold circulating air—may be a contributing factor to the contagious virus. make covid-19 faster-19 spread

Linsey Marr, an engineering professor from Virginia, said: “On a nice day, We rarely use heaters or air conditioners. and when you turn on the air conditioner you are circulating the air This could allow airborne viruses to form.” Tech, who studied how well the coronavirus can survive under various heat and humidity conditions, “the question of airflow is comparable to masks and vaccines.” The determinant of diffusion, Dr. Mar said.

Outdoor time and environmental issues such as humidity and air circulation are far from the only factors. Vaccination rates play a huge role. and masked orders restricting public gatherings And geographical features such as population density are also important factors. public health experts say

A nurse vaccinates against COVID-19 on April 7 in Clarksdale. Mississippi States with a 7-day average of new cases have declined about 72% since March 1.


Rogelio V. Solis/Related News

But numerous scientific studies have shown that COVID-19 is not spreading as quickly as it does indoors. This is mainly because the virus particles spread in more open spaces. Some studies also indicate that exposure to sunlight can cause the virus to stop working. A systematic review of a study on invasive conditions published in February by the Journal of Infectious Diseases found that indoor SARS-CoV-2 transmission rates were nearly 19 times as high as those of metastases. external A December study found that 94% of superspreader events In the United States it occurs in an indoor environment with limited ventilation.

Another factor that researchers understand more is humidity. According to an October study co-authored by Dr. Marr, which has not yet been peer-reviewed, viruses such as SARS-CoV-2 contained within lipid membranes thrive in environments with relative humidity below 40%. while being less stable and dispersing less as the air humidity rises above that level.

Dr Mar said indoor humidity varies with outdoor temperatures. During the cold winter and early spring of the Northeast, for example, a gas heating system dries the indoor air. by reducing the relative humidity to only 10% to 20%, while in the south during the same season Indoor humidity is generally high. About 60% higher, according to research by Dr. Marr, humidity is also reduced to about 30% with heavy use of air conditioners. which doubles the risk for the spread of COVID-19 Because it will circulate the air inside the building as well.

“That’s why last summer,” Dr Marr said. So we saw several initial surges in the Sunbelt, where the heat was intense. And everyone is turning on the air conditioner,” said Dr. Marr.

Akiko Iwasaki, an immunologist at Yale University. that studies viruses and the environment It states that lower humidity also weakens the body’s immunity against pathogenic viruses.

The body’s primary response to two viruses is a process known as mucociliary clearance, in which hairy tendons expel the virus from the lung tissue. and the production of immune cell cytokines that limit viral replication. Hindered by humidity levels below 40%, research has found.


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Dr. Iwasaki said “This is something that might explain the seasons of viruses like the flu and the flu. And why does this happen more often than during the winter? As people spend more time in arid environments, she added, “nothing can replace a vaccine in terms of protection” from Covid-19.

How well can southern states with low vaccination rates crack down on Covid-19 cases in the summer? It can improve our understanding of the role of outdoor effects and humidity.

“I think you’re going to see a summer surge in Georgia,” said Carlos Del Rio, an infectious disease physician and associate dean of Emory University School of Medicine in Atlanta. But the question is how much?”

Health officials in warmer states have launched a public information campaign to encourage residents to spend as much time outdoors and are pushing for more vaccinations at outdoor sites such as state parks and baseball parks. small leagues to head out elsewhere Summer that could happen this year

Brannon Traxler, an epidemiologist who heads the South Carolina Department of Public Health, said: “Vaccination and people spending time outdoors are the two biggest factors.” Why is the number of cases relatively low this spring?

Encouraging people to spend time outdoors is a top priority. But more importantly, the focus is on vaccination. The weather and where and how people congregate has become less of a problem.”

write to Robbie Whelan at Robbie.whelan@wsj.com

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