Friday , January 15 2021

Why deaths are not growing so fast in the second wave of Covid-19, despite the big jumps of new infections

Recent case and fatality figures from the European Center for Disease Prevention and Control (ECDC) show that while Covid-19 cases are on the rise in the UK, France, Spain, Germany and other European countries, with deaths not growing at the same rate.

“The mortality rate has dropped, in the UK we can see it declining from around June to a low in August,” said Assison Oke, a senior statistician at the Nafield Department of Health Sciences for Primary Health Care. “Our current estimate is that the mortality rate from infections is rising slightly, but it has not appeared anywhere near where we were and that is unlikely to change dramatically unless we see a really surprising increase in the number of deaths.”

Oke tracked the death rates of Covid-19 along with his colleague Carl Hennegan of the Center for Evidence-Based Medicine and health economist Daniel Hodon. Their research shows that, at the end of June, the mortality rate was just under 3% in the UK. By August, it had fallen to about 0.5%. It is now about 0.75%.

“We think it probably varies a lot according to age, but also other factors, such as treatment,” Oke said.

The lower mortality rate is not unique to Europe.

In New York, mortality rates for those hospitalized with coronavirus-related illnesses have also fallen since the beginning of this year, according to a study by a team of researchers at New York Grossman School of Medicine published in the Journal of Hospital Medicine.

Younger, healthier people become infected

The most obvious reason for the lower number of victims is age.

The first wave of the pandemic particularly affected older people in Europe, spreading to hospitals and nursing homes, but this changed over the summer, with the virus circulating more widely among younger people going to restaurants, bars and other public places.

The median age of those infected across Europe dropped from 54 in January to May to 39 in June and July, according to the ECDC.

The number of older people getting coronavirus in Europe is rising again.  That's really bad news

Older people are at a much higher risk of becoming seriously ill if they become infected, so an epidemic affecting a nursing home is likely to be much more deadly than a college epidemic.

In fact, data collected by researchers at the London School of Economic Response to Long-Term Care for the Covid-19 Group show that, on average, 46% of all Covid-19 deaths across 21 countries occurred in foster care.

Researchers have found that in several countries, including Belgium, Ireland, Spain, the United Kingdom and the United States, the proportion of people in coronavirus-related nursing homes is more than 4% in some cases. This means that more than one in 25 foster care residents who have died since the pandemic began did so because of Covid-19.

By infecting more young people, the overall mortality rate has dropped, but that does not mean the virus itself has become less deadly. If it starts to spread widely among older people again, the rate may increase again. This is already happening in some countries, including the UK where Oke and his colleagues have seen a slight increase in the death rate.

“The Covid-19 virus is very stable, it does not mutate much at all,” said Dr Julian Tang, a clinical virologist and honorary associate professor at the University of Leicester. “The variation in the severity of Covid-19 disease is really due to the host’s individual immune responses along with age, gender, ethnicity and certain pre-existing medical conditions,” he added.

Treatments are improving

Demographic change may contribute to fewer casualties, but experts doubt that the fact that health care providers are now more experienced in dealing with Covid-19 patients is another factor.

“As long as Covid-19 remains a terrible disease, our efforts to improve treatment are likely to succeed,” said Dr. Leora Horwitz, lead author of the New York study, and associate professor in the Department of Public Health in New York Langon Health.

Horwitz and her team found that, when adjusted for demographic and clinical factors, mortality among inpatients under the NYU system fell from 25.6% in March to 7.6% in August.

The treatment of coronavirus patients has also changed. Fans, which were used very early in the pandemic, are now used less because doctors have learned more about how they can injure the lungs of patients with Covid-19. In turn, lying face down on the abdomen has become more common, as it has been shown to help increase the amount of oxygen entering the lungs of some patients.

Statistics show that people who end up in a hospital in the UK are experiencing better results.

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The National Center for Intensive Care Review and Research found that Covid-19 patients treated in intensive care units in England, Wales and Northern Ireland after September 1 had a much higher chance of survival than those admitted before: 12% of patients died early. in September, compared with 39% of applications since the beginning of the pandemic and the end of August.

“It suggests that either treatment is better [the healthcare workers] “Now know what to do, or possibly people with milder symptoms.”

And while there is still no cure for silver coronavirus, there are some treatment options that seem to help some patients.

Antiviral remedisivir is approved by the US Food and Drug Administration for the treatment of coronavirus infection.

Earlier this month, a global study sponsored by the World Health Organization found that remedisivir did not help patients survive or even recover faster, but a US study found that the drug shortened the recovery time of some patients by about a third. .

Dexamethasone, a steroid, has been used in some of the sickest Covid-19 patients who need ventilation or oxygen after studies have shown it may increase their chances of survival.

Data and testing questions

While lower mortality rates may seem encouraging, there are many warnings to consider. Mortality from Covid-19 is calculated as the number of deaths out of the total number of infections, which means that it is accurate only if the basic figures reflect reality.

And this was almost certainly not the case early in the pandemic, when testing was not widely available and only those who were seriously ill were tested.

“If you test only symptomatic cases, you can massively underestimate the number of infected if the percentage of asymptomatic cases is high,” Tang said, adding that some studies suggest that up to 60% to 70% of Covid-19 cases may be asymptomatic. .

“So the reported [case fatality rate] “It may be disproportionately high at the beginning of a pandemic, but then it falls as the pandemic progresses, as we test more asymptomatic cases to ‘dilute’ this apparent mortality rate.”

The main danger, Tang said, is that widespread testing of the less vulnerable younger population could mask mortality rates in those who are older or have basic conditions. “There is a risk of complacency,” he said. “The elderly and vulnerable will still die from complications related to Covid-19 … but this may not be noticed if all age groups with COVID-19 are examined together.

Mortality rates also vary from country to country. According to a Johns Hopkins University calculation, mortality among the 20 most affected countries now ranges from 10% in Mexico to 0.8% in the Czech Republic. This is partly due to the different approaches to counting their Covid-19 cases. While some consider only laboratory-confirmed infections, others include unverified suspected cases.

There is also the issue of time lag. “The time difference between when we think people get infected and when they can die is about three weeks on average, but what we see is that [infection fatality rate] “It stays lower even when previous infections have increased.”

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