Mardi Gras 2020 generated up to 50K cases of coronavirus, probably from one source, according to study Coronavirus

Public health officials have largely accepted that last year’s Mardi Gras helped make New Orleans an early coronavirus hotspot in the US, even though a lack of testing made it difficult to be sure.

But a new study that wanted to determine how the virus spread through the city found that the 2020 carnival was responsible for tens of thousands of cases of coronavirus, after a single person probably brought it to New Orleans in the weeks before Mardi Gras .

Researchers at the Scripps Research Institute, Tulane University, LSU Health and several other institutions said in a pre-publication report on Monday that the coronavirus probably arrived in New Orleans two weeks before Fat Tuesday, most likely from a person traveling from Texas has.

They found that nearly 800 people were likely infected by people dying on Ash Wednesday and that the new infections had sown most of the 50,000 confirmed cases in Louisiana’s first wave over the next few months.

“The whole outbreak in Louisiana is almost certainly fueled by what happened on Mardi Gras,” said Mark Zeller, study author and a researcher at Scripps. ‘It’s basically the snowball. Once it goes, it just goes. It’s really hard to stop. ”

The newspaper, which has not yet been peer-reviewed, used death data to retrospectively model how many cases the city would have had. It used genome sequencing to trace the cases to a single source and cell phone tracking data to simulate the spread.

The findings, taken with previous studies and reports, focused on the distribution in New Orleans, and added further evidence that Mardi Gras was a super-spreading event that changed the form of the pandemic, both in Louisiana and in the southern United States. .

And that suggests that Carnival’s timing could hardly have been worse, with the festivities picking up steam just before federal officials recommended the closing period. It was also a period in which providers had little experience treating coronavirus patients and a limited ability to test and detect exposure.

“In March, I think New Orleans had the largest increase in patients anywhere in the world,” Zeller said. ‘It’s just a very unfortunate timing. If Mardi Gras had been two, three weeks earlier, it might not have resulted in so many cases. ”

The virus spreads through New Orleans unlike other cities with early spikes, such as Seattle and New York City. In those places, several people probably brought in slightly different strains over a short period of time and sowed mini-outbreaks that quickly exploded.

But based on the investigation’s investigation into the genetic diversity of the virus found in New Orleans, Mardi Gras actually created cruise ship-like conditions, where a single variety of the virus quickly spreads wild from one source.

“It’s the same kind of situation,” said Robert Garry, a Tulane University virologist and co-author of the article. “A cruise ship, people are crammed into smaller spaces, people are in these confined areas,” Garry said. ‘Almost like with a Mardi Gras crayfish, right? People spend a lot of time together, in the balls, in the nearby spaces. ”

Garry said international travelers in other cities have brought tension from different places. But when scientists mapped the spread of the virus based on genetic similarities between the cases, they found that the same was not true in Louisiana.

“People were worried that a lot of travelers from Asia and Europe would come in to set up different tribes, it didn’t happen,” Garry said. “It tells us how the virus spreads – when people come to nearby spaces, talk and shout and have a good drink, this is where it spreads.”

According to Jeremy Kamil, a professor of microbiology and immunology at LSU Health, who distributed only one main strain, it was luck and timing that helped coordinate the order of coronavirus test samples. Louisiana’s unique single-stemmed pattern helped illuminate the reach of Mardi Gras as a super-spreader.

“It’s like a spark,” says Kamil. “In Louisiana, there happened to be more than one introduction, but only one caught fire.”

Although larger areas, such as Houston, had more strains of the virus, Mardi Gras seemed to have a chain of transmission that formed the path of the pandemic when it tore through New Orleans, making it a city with the highest deaths per capita at times.

In some ways, it was fortunate that only one tribe took office. But it took off at the most opportune time for a virus – when people crowded into crowds, shared drinks and food, shouted and sang with little thought to a respiratory virus.

“It was a lovely place in the pandemic because it was a very early stage,” Kamil said.

Like humans, viruses transmit certain traits to each other. When scientists analyze all these differences, a picture begins to emerge, just like ancestors on a family tree.

“If you do that with the New Orleans tribes, they appear on one branch of the tree,” Garry said, “which means they were related.”

The article compares 235 Louisiana genome series with series from other parts of the country and the world. More than 30,000 pieces of each virus were analyzed and compared so that scientists could connect the points between the transmission.

The article also introduces the idea that Mardi Gras has caused contagious infections across the US. The virus strain in New Orleans has spread seed infections throughout the south – to other parts of Louisiana, Mississippi, Texas and Alabama – but restrictions remain at home and restrict air travel seems to spread to other regions.

As the city looks ahead to a Mardi Gras that will look very different this year with closed bars, restricted pedestrian traffic and banned heads, the authors hope their findings will be a warning about the downstream effects of collection as the virus circulates. .

With new, more transferable variants in circulation, the transfer chain is even harder to break.

“If students gather in Bourbon Street, many of the people will not get seriously ill,” Kamil said. ‘But if they’re going to visit grandma, or if they’re spreading it to someone else who’s spreading it to someone else working in a nursing home or a prison worker, then you’re suddenly indirectly involved in a chain of events where you’re now somehow participated in the deaths of 90 people. ”