Washington (PTI): Scientists have uncovered details about the reason behind loss of smell continuing as part of long Covid symptoms, according to a new study.
The reason some people fail to recover their sense of smell after COVID-19 is linked to an ongoing immune assault on olfactory nerve cells and an associated decline in the number of those cells, a team of scientists from Duke University, US, report.
Olfactory nerve cells are associated with our ability to distinguish scents and smells.
The findings, published in the journal Science Translational Medicine, provide an important insight into a vexing problem that has plagued millions who have not fully recovered their sense of smell after COVID-19, the study said.
While focusing on the loss smell, the findings also shed light on the possible underlying causes of other long COVID-19 symptoms - including generalized fatigue, shortness of breath, and brain fog - that might be triggered by similar biological mechanisms.
"One of the first symptoms that has typically been associated with COVID-19 infection is loss of smell," said senior author Bradley Goldstein, Duke University.
"Fortunately, many people who have an altered sense of smell during the acute phase of viral infection will recover smell within the next one to two weeks, but some do not," said Goldstein.
"We need to better understand why this subset of people will go on to have persistent smell loss for months to years after being infected with SARS-CoV-2," said Goldstein.
In the study, Goldstein and colleagues at Duke, Harvard and the University of California-San Diego analyzed olfactory epithelial samples collected from 24 biopsies, including nine patients suffering from long-term smell loss following COVID-19.
This biopsy-based approach revealed widespread infiltration of T-cells engaged in an inflammatory response in the olfactory epithelium, the tissue in the nose where smell nerve cells are located. This unique inflammation process persisted despite the absence of detectable SARS-CoV-2 levels, the study said.
Additionally, the number of olfactory sensory neurons were diminished, possibly due to damage of the delicate tissue from the ongoing inflammation, the study said.
"The findings are striking," said Goldstein. "It's almost resembling a sort of autoimmune-like process in the nose."
Goldstein said learning what sites are damaged and what cell types are involved is a key step toward beginning to design treatments. He said the researchers were encouraged that neurons appeared to maintain some ability to repair even after the long-term immune onslaught.
"We are hopeful that modulating the abnormal immune response or repair processes within the nose of these patients could help to at least partially restore a sense of smell," said Goldstein, noting that this work was currently underway in his lab.
He said the findings from this study could also inform additional research into other long-COVID-19 symptoms that might be undergoing similar inflammatory processes.
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Jaipur, Mar 28: Young Riyan Parag showed why he is considered a precocious talent as he struck a stunning 84 not out off 45 balls to set up a 12-run win for Rajasthan Royals against Delhi Capitals in their IPL match here on Thursday.
Sent in to bat, RR were reduced to 36 for 3 in the eighth over but the 22-year-old Parag single-handedly took the home side to 185 for 5 with a magnificent unbeaten knock studded with seven fours and six sixes.
Parag, who was promoted to number 4 by the team management this season and made 43 in the previous match, took 25 runs off veteran South African pacer Anrich Nortje with scores of 4, 4, 6, 4, 6, 1 in the final over to hit his highest T20 score.
Chasing 186 for a win, DC could only manage 173 for 5 in 20 overs though South African youngster Tristan Stubbs (44 not out off 23 balls) kept them in the hunt till the final over from which they needed 17 runs.
Avesh Khan conceded just four runs to help RR win their second consecutive match.
South African pacer Nandre Burger and Yuzvendra Chahal took two wickets apiece to also contribute in the RR win.
"Definitely disappointed. The best thing to do from here is to learn from it. The bowlers did well through the 15-16 overs. But the batters did well at the death, hopefully we do better in the next game," DC skipper Rishabh Pant said.
DC were reduced to 34 for 2 in the fourth over with Burger taking two wickets in three balls in a fine display of fast bowling.
Burger, who was brought in as Impact Sub for Shimron Hetmyer, dismissed opener Mitchell Marsh (23 off 12 balls) and Ricky Bhui (0) in the fourth over.
DC captain Rishabh Pant came out to bat at the fall of Bhui's wicket and along with senior batter David Warner built the innings without taking too much risk. Delhi were 89 for 2 at the halfway stage.
Warner was the more aggressive one as he got the boundaries to keep DC in the hunt. The senior Australian batter fell one run short of his fifty courtesy a brilliant diving catch by Sandeep Sharma off the bowling of Avesh in the 12th over.
Warner and Pant were involved in a crucial 67-run partnership for the third wicket.
Playing in his 100th IPL match and 14 months after a horrible car crash, Pant tried to build the innings with occasional boundaries. But he got out for a 26-ball 28 as Chahal induced a faint lower edge for Sanju Samson to do the rest behind the stumps in the 14th over.
The asking rate shot up to more than 13 runs an over and DC needed 66 from the last five overs.
Stubbs kept DC in the game with two consecutive sixes off Ravichandran Ashwin in the 17th over, but in the end the Delhi side were short by 12 runs.
They needed 34 runs from the final two overs which they could not get. It was DC's second consecutive loss.
Earlier, Parag shared 54 and 52 runs respectively with Ravichandran Ashwin (29) and Dhruv Jurel (20) after RR made a shaky start.
Royals captain Samson struck three consecutive boundaries in the fourth over bowled by pacer Mukesh Kumar before nicking a Khaleel Ahmed delivery two overs later to Pant to get out for 15.
RR were 30 for 2 by then as Mukesh had given DC their first breakthrough with the wicket of Yashasvi Jaiswal (5).
The Royals were in more trouble after wrist spinner Kuldeep Yadav literally forced his captain Pant to take a review, which later proved to be successful, to dismiss Englishman Jos Buttler for an LBW decision.
Ashwin came out to bat at number five and he lofted a Kuldeep delivery for a six to help RR reach 58 for 3 at halfway stage. He gave Nortje even a harsher treatment with two sixes in the next over that yielded 15 runs.
Ashwin, however, holed out to Tristan Stubbs near the boundary ropes for a 19-ball 29.
Parag then made his presence felt, striking two boundaries and a six off Ahmed to take RR past 100 in the 15th over.