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COVID-19 may be more deadly than previously thought: three symptoms raise new questions

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The devastating first wave of the Covid-19 outbreak hit the United States with unparalleled ferocity two years ago. The terror’s intensity can be difficult to recall, and it’s unlikely to happen again thanks to breakthroughs in diagnosis, treatment, and vaccine.

Scientists, on the other hand, must return to the dark period and reconsider what happened by studying the seemingly limitless data obtained in order to better comprehend both the immediate and long-term impacts of this sickness on the body.

One important piece of knowledge came from autopsy records, which showed how the virus affects different organs in the body.

Many doctors believe progressive pneumonia with lung loss is the cause of so many fatalities due to respiratory failure. Blood clots in the lungs, on the other hand, were discovered by researchers (also referred to as pulmonary emboli). In addition, they discovered a slew of tiny clots in a variety of other organs.

COVID-19 may be more deadly than previously thought: three symptoms raise new questions
COVID-19 may be more deadly than previously thought: three symptoms raise new questions

A new Swedish study published today in The BMJ indicates an increased risk of deep vein thrombosis (blood clots in the leg) up to three months after covid-19 infection, pulmonary embolism (blood clots in the lung) up to six months, and a bleeding event up to two months after covid-19 infection.

The data also reveals that patients with underlying diseases (comorbidities), those with more severe covid-19, and patients in the first pandemic wave have a higher risk of events than those in the second and third waves.

These findings, according to the researchers, encourage measures to prevent thrombotic events (thromboprophylaxis), particularly in high-risk individuals and emphasize the relevance of covid-19 immunization.

Covid-19 is well established to raise the risk of serious blood clots (also known as venous thromboembolism or VTE), although there is less data on the length of time this risk is enhanced, whether risk varies during pandemic waves, and whether covid-19 also increases the risk of major bleeding.

To address these issues, researchers set out to assess the risk of deep vein thrombosis, pulmonary embolism, and hemorrhage after covid-19 administration.

Between 1 February 2020 and 25 May 2021, they identified over one million people with confirmed SARSCoV-2 infection (the virus that causes covid-19) using Swedish national registries and matched them by age, sex, and county of residence to over four million people who had not had a positive SARS-CoV-2 test result.

They then conducted two analyses: the first compared the incidence of deep vein thrombosis, pulmonary embolism, and hemorrhage in covid-19 persons throughout a control period (before and long after covid-19 diagnosis) to the rates in different time intervals after covid-19 diagnosis (days 1-7, 8-14, 15-30, 31-60, 61-90, and 91-180).

In the second analysis, they estimated the rates of deep vein thrombosis, pulmonary embolism, and hemorrhage in the covid-19 group from 1 to 30 days following diagnosis and compared them to the control group’s comparable rates.

The findings demonstrate that, when compared to the control period, the risks of deep vein thrombosis, pulmonary embolism, and hemorrhage were significantly higher 90 days after covid-19, 180 days after covid-19, and 60 days after covid-19.

After controlling for a variety of potential confounding variables, the researchers discovered a fivefold rise in the chance of deep vein thrombosis, a 33fold increase in the risk of pulmonary embolism, and a nearly twofold increase in the risk of bleeding in the 30 days following infection.

In absolute terms, this means that a first deep vein thrombosis occurred in 401 patients with covid-19 (absolute risk 0.04%) and 267 control patients (absolute risk 0.01%). A first pulmonary embolism event occurred in 1,761 patients with covid-19 (absolute risk 0.17%) and 171 control patients (absolute risk 0.004%), and a first bleeding event occurred in 1,002 patients with covid-19 (absolute risk 0.10%) and 1,292 control patients (absolute risk 0.04%).

Risks were highest in patients with more severe covid-19 and during the first pandemic wave compared with the second and third waves, which the researchers say could be explained by improvements in treatment and vaccine coverage in older patients after the first wave.

Even among mild, non-hospitalised covid-19 patients, the researchers found increased risks of deep vein thrombosis and pulmonary embolism. No increased risk of bleeding was found in mild cases, but a noticeable increase was observed in more severe cases.

This is an observational study, so the researchers cannot establish cause, and they acknowledge several limitations which might have affected their findings. For example, VTE may have been underdiagnosed in patients with covid-19, testing for covid-19 was limited, especially during the first pandemic wave, and information on vaccination was not available.

However, results were largely consistent after further analyses, and are in line with similar studies on the association between covid-19 and thromboembolic events, suggesting that they withstand scrutiny.

As such, the researchers say their findings suggest that covid-19 is an independent risk factor for deep vein thrombosis, pulmonary embolism, and bleeding, and that the risk of these outcomes is increased for three, six, and two months after covid-19, respectively.

“Our findings arguably support thromboprophylaxis to avoid thrombotic events, especially for high risk patients, and strengthen the importance of vaccination against covid-19,” they conclude.

In a linked editorial, researchers at the University of Glasgow point out that despite the potential for new variants of concern, most governments are removing restrictions and shifting their focus to determining how best to “live with covid.” 

However, they say this study “reminds us of the need to remain vigilant to the complications associated with even mild SARS-CoV-2 infection, including thromboembolism.”

Image Credit: Getty

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