Coronavirus Buildup In Lungs Likely Driver Of Covid Deaths:
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Viral buildup in the lungs is the likely driver behind the steep mortality rates seen in the COVID-19 pandemic, according to a study. The researchers showed that people who died of COVID-19 had on average 10 times the amount of virus in their lower airways as did severely ill patients who survived their illness. The finding, contradicts previous theories that simultaneous infections, such as bacterial pneumonia or overreaction of the body's immune defence system, played major roles in heightened risk of death.

The researchers found no evidence implicating a secondary bacterial infection as the cause of the deaths, although they cautioned that this may be due to the frequent course of antibiotics given to critically ill patients. Despite previous concerns that the virus may prompt the immune system to attack the body's own lung tissue and lead to dangerous levels of inflammation, the researchers found no evidence that this was a major contributor to COVID-19 deaths in the group studied.

They noted that the strength of the immune response appeared proportionate to the amount of virus in the lungs. The coronavirus has so far killed over 4 million people worldwide. Those placed on mechanical ventilators in order to breathe fare particularly poorly. The latest study provides the most detailed survey of the lower airway environment in coronavirus patients, the researchers said. They collected bacterial and fungal samples from the lungs of 589 men and women who were hospitalised in the US, all of whom required mechanical ventilation.

For a subset of 142 patients who also received a bronchoscopy procedure to clear their air passages, the researchers analysed the amount of virus within their lower airways and identified the microbes present by studying small pieces of the germs' genetic code. They also surveyed the type of immune cells and compounds located in the lower airways.

The study revealed that those who died had on average 50 percent lower production of a type of immune chemical that targets the coronavirus compared with the COVID-19 patients who survived the illness. These customised proteins are part of the body's adaptive immune system, a subset of cells and chemicals that "remember" invading newly encountered microbes, leaving the body better prepared for future exposure.

"These results suggest that a problem with the adaptive immune system is preventing it from effectively combating the coronavirus," said study senior author Leopoldo Segal. "If we can identify the source of this issue, we may be able to find an effective treatment that works by bolstering the body's own defenses," said Segal, an associate professor at NYU.

Source:
https://www.nature.com/articles/s41564-021-00961-5
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