Public health officials largely agreed that last year’s Mardi Gras helped establish an early coronavirus hotspot in New Orleans in the United States, even though it was difficult to ascertain due to a lack of tests.
But a new study aimed at determining how the virus spread in the city found that the carnival party of 2020 caused tens of thousands of cases of coronavirus after a single man was probably brought to New Orleans from the pre-Mardi Gras weeks.
Researchers at Tulane University, the Scripps Research Institute, LSU Health and several other institutions said in a preliminary report released Monday that the coronavirus probably arrived in New Orleans about two weeks before Fat Tuesday, probably from a person traveling from Texas.
It was found that nearly 800 people were likely to be infected by the mass of time that died on Ash Wednesday, and that these new infections carried forward most of the 50,000 confirmed cases reached in the first wave of Louisiana in the coming months.
“The Louisiana epidemic will almost certainly fuel what happened at Mardi Gras,” said Mark Zeller, author of the study and Scripps researcher. – It’s basically a snowball. Once you go, you just go. It’s very hard to stop. “
The paper, which has not yet passed the peer review, used the death data to retrospectively model how many cases the city would have had. Using genome sequencing, cases were applied to a single source and cell phone tracking data to help simulate propagation.
Findings from previous studies and reports focusing on prevalence in New Orleans added further evidence that Mardi Gras was a superspreading event that changed the shape of the epidemic, both in Louisiana and in the southern United States.
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And he hints that the timing of the carnival would hardly have been worse, as the festivities picked up steam just before the shutdown, before federal officials recommended it. This was also a period when providers had little experience in treating coronavirus patients and had limited ability to test and monitor exposure.
“In March, I think New Orleans saw the strongest increase in the number of patients anywhere in the world,” Zeller said. – It’s just a very unfortunate timing. If Mardi Gras had been two or three weeks earlier, he might not have had so many cases.
The virus spread differently in New Orleans than in other early spiky cities such as Seattle and New York City. In these places, more people were likely to have brought slightly different tribes in a short time, causing rapidly exploding mini-epidemics.
But the study, based on an examination of the genetic variant of the virus present in New Orleans, created Mardi Gras essentially sea-going ship-like conditions where a single type of virus spreads rapidly wildly from a single source.
“It’s the same situation,” said Robert Garry, a virologist at Tulane University and one of the paper’s lead authors. “On a cruise ship, people are trapped in smaller spaces, people are in these enclosed areas,” Garry said. “It’s almost like a Mardi Gras krewe, isn’t it?” People spend a lot of time together, at balls, in those nearby places. “
Garry said international travelers in other cities have brought loads from different places. But when scientists mapped the spread of the virus based on the genetic similarities between the cases, they found that this was not true in Louisiana.
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“People were worried that a lot of travelers would come from Asia and Europe and bring in different tribes, that didn’t happen,” Garry said. “It reveals the way the virus spreads – when people get into nearby spaces, talk, shout, have fun, drink, it spreads there.”
According to Jeremy Kamil, a professor of microbiology and immunology at LSU Health who helped coordinate the sequencing of coronavirus test samples, there was only one major strain of luck and part-time. Louisiana’s unique trunk pattern helped illuminate the range of the Mardi Gras.
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“It’s like a spark,” Kamil said. “There were several introductions in Louisiana by accident, but only one caught fire.”
Although there were several virus strains in larger areas, such as Houston, Mardi Gras seemed to have started a chain of transmission that transformed the path of the pandemic when it broke through in New Orleans, making it a city where per capita deaths were highest. times.
In some ways, he was lucky to be caught by only one tribe. But it was sustained at the most opportune time of the virus — when people were crowded, drinks and food were distributed, yelled, and sung, they didn’t think about the respiratory virus.
“It’s a sweet spot in the pandemic because it was a very early stage,” Kamil said.
The Louisiana Department of Health reported 867 additional confirmed cases of coronavirus and another 18 confirmed deaths at noon on Tuesday.
Like humans, viruses pass certain properties to each other. When scientists analyze these differences, an image begins to form, just like the ancestors on the family tree.
“When you do this with the New Orleans tribes, they appear on one branch of the tree,” Garry said. “Which means they’re related.”
The study compared 235 Louisiana genome sequences with sequences from other parts of the country and the world. More than 30,000 pieces of each virus were analyzed and compared to allow scientists to link the points between transmission.
The article also supports the idea that Mardi Gras has spread infections in the United States. The New Orleans virus strain has caused seed infections all over the south – in Louisiana, Mississippi, Texas and other parts of Alabama – but staying home restrictions and limited air travel appear to have prevented it from spreading to other regions.
As the city faces a Mardi Gras that looks very different this year, with bars closed, pedestrian traffic restricted and cups banned, the study’s authors hope their findings serve as a warning of the downstream effects of gathering as the virus circulates. .
The new, more transferable versions on the market make it even harder to break the transmission chain.
“If college students crowd on Bourbon Street, many will not suffer from a serious illness,” Kamil said. “But if you go home and visit your grandmother, or if you distribute it to someone else who distributes it to someone who works in a nursing home or is a prison employee, you’re suddenly indirectly involved in an event where you’ve somehow been involved in 90 deaths. “