At the end of March, the death rate in Italy, Europe`s new crown outbreak center, reached an alarming 11%. At the same time, neighbouring Germany has a death rate of only 1 per cent, while China has a death rate of 4 per cent, while Israel has the lowest rate of 0.35 per cent worldwide.
Amazingly, the same virus does not appear to mutate significantly due to transmission, but the death rate varies considerably. Even within a country, the ratio seems to change over time. Why?
several major factors contribute roughly to these differences, the most important reason being how we detect and identify new crown cases.
Different definitions
First there is confusion about the definition of "death rate ". Even if the death rate is the same, the numbers look very different.
actually there are two death rates. First, the proportion of the population death tested positive is the "fatality rate ". A second category is the proportion of the population death overall post-infection, but many of them are not included in the number of confirmed cases, which is only a valuation, which is the "infection death rate ".
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The case fatality rate describes how many people can be determined to have died from the infection and how many people the virus causes overall death. explains Oxford University epidemiologist Carl Heingen (Carl Heneghan). He is also a general practitioner who is suspected of being infected with the new crown virus and is recovering.
For example ,10 of 100 people infected with the new crown virus tested positive in hospitals. 90 others were not tested, including one inpatient death ,99 others.
This brings the mortality rate to one tenth, or 10 per cent. but the infection death rate was only 1%, i.e .1%.
As a result, if some countries/territories test only those who are seriously ill and not those who are not hospitalized with mild (or even asymptomatic) patients (as the United Kingdom currently does), their death rates are higher than those in countries where extensive testing is undertaken (e.g. Germany or Korea).
Impact of detection
While carefully comparing the same type of death rates across countries/regions, it is easy to see how many people tested change the final result.
Dietrich Rotenbach (Dietrich Rothenbacher), Director of the Institute of Epidemiology and Medical Biostatistics, University of Ulm, Germany, said that in practice most countries lack extensive and systematic testing, which is the main reason for the difference in international death rates.
He said that the current national figures were "simply not" directly comparable. In order to obtain accurate figures for the entire population, it is necessary to test not only symptomatic cases, but also asymptomatic infections. These data provide an accurate picture of how pandemics affect the entire population, not just the sick.
When the patient has not been tested for new coronavirus, but is still a suspicious case, the situation is even more unclear.
He said :" There is currently a significant bias in data across countries, so data can not be compared directly. We need effective and comparable figures, which are efficient and systematic approaches to selecting representative sampling structures. "
An example from Vo villages in northern Italy shows that testing is important not only to obtain accurate data, but also to curb the new crown virus. After the first case of the new coronavirus was confirmed in Vo village, the test was carried out to the entire village of 3300 people. The results showed that at the time of the "first case ",3 per cent of the village`s population had been infected when they had no or only very mild symptoms.
A similar situation was demonstrated by extensive tests in Iceland. To date, Iceland has tested more than 3 per cent of the population of some 365,000 people, both symptomatic and asymptomatic. It is estimated that 0.5 per cent of the population in Iceland may be infected with the new crown virus. Heinegen points out that even this number may be (slightly lower than actual) because asymptomatic people are unlikely to be tested. The actual figure may be close to 1 per cent of the Icelandic population, which means that there are about 3650 cases of infection.
another difficulty is that these data are not from peer-reviewed research data but almost real-time clinical data. Clinical data can be messy and there are a lot to pay attention to. these figures highlight the importance of extensive testing to help alert public health measures, says Sheila Bird of the university of cambridge`s MRC biostatistics department (University of Cambridge`s MRC Biostatistics Unit).
"If you`ve never had a real symptom, but you` ve been infected, it`s an infection ," Bird said. It`s an` uncountable` infection before we find an effective antibody test. "
antibody tests can detect traces of response to the immune system to the virus and reveal who is infected with the virus. these tests are tools to change the rules of the game that can reveal who is immune to the virus and can safely return to daily life without the risk of infection or transmission of the virus. "That`s why the development and deployment of the test is so important ," Bird said. "
After two weeks in Vo village, the transmission of the new crown virus stopped, because extensive testing and strict follow-up measures can be targeted to contain the infection. Iceland has so far had only two cases death new coronavirus.
Other factors
and other factors will change death the rate.
Among them is the number of new coronavirus death doctors actually identify. At first glance, it seems simple: if patients become infected with the new crown virus death, then they are thought to have died of the new crown virus.
But if they themselves suffer from diseases such as asthma, the role of the new crown virus is to aggravate the condition? Or, if a patient dies of a respiratory disease that appears to be unrelated to the new coronavirus, such as a cerebral aneurysm, how do these conditions determine the cause of death?
Even in the same country/region, official statistics vary depending on how they are calculated. The British Department of Health and Social Care (The Department of Health and Social Care), for example, updates and publishes daily numbers death new crown virus positive tests, including any patients who are positive for new crown virus tests but may die from other diseases, such as advanced cancer. The UK`s Office for National Statistics, however, counted all death death of the new coronavirus mentioned on the certificate, whether they were tested or simply suspected.
The non-synchronization of data from the National Bureau of Statistics and the Department of Health and Social Care in the UK adds complexity to the perception of death rates. The counting method of the British national Bureau of Statistics can only be carried out after the issuance of death certificates, so it takes longer.
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The British head of national Bureau of Statistics death rate analysis, Sarah Kaul (Sarah Caul), wrote on her blog that death statistical methods do not include :" The problem is not right or wrong, but that each data source has its own advantages and disadvantages. "
However, this is not necessarily the root cause of the differences between the majority of countries, as many calculate death numbers in the same way. Italy regards death of any person with the new crown virus as caused by the new crown virus death; as do Germany and Hong Kong.
Doctors in the United States have more autonomy to decide: when they report new cases of crown death to CDC, they are asked to record whether the patient died "as a result of the disease ". And it`s easy to see how doctors judge a patient`s death, such as a heart attack or a cerebral aneurysm, is not due to the new coronavirus death, so this is not reported.
Nearly a quarter of Italy`s population is over 65, compared with just 11% in China.
Importantly, data analysis from months or years from now may vary, and in the u.s., the death of any new-crowned virus patient is now included in publicly reported new-crowned death cases, regardless of whether a doctor decides to die directly from it.
"My hope is that the final certificate of death for new crown infections will include a history of past illness ," said CecileViboud, an epidemiologist at the National Institutes of Health International Centre (Fogarty International Center at the National Institutes of Health). But any death cases currently tested positive are included in the U.S. death statistics. "
How to determine the true case death new coronavirus in the long run will affect our macro understanding of its lethality. This has not yet been taken seriously.
Complex cases
The situation is even more unclear when the patient has yet to undergo a new coronavirus test but is suspicious. Since the new crown virus causes many people with past medical history death, doctors still need to identify death cause.
Within an epidemic, doctors are likely to attribute the death responsible for the case to the disease still under discussion, the detection error (ascertainment bias).
"Every case of death is thought to be associated with a new crown virus in an epidemic ," Heineken said. But that is not the case. overall, when people review case descriptions and determine causal relationship, they realize that they overestimate disease-related case death rates. "
The reason for this bias is that "there is a tendency towards the worst. this is the only message passed to us. "
An example is the 2009 H1N1 pandemic (swine flu). Early case death rates are overvalued by more than 10 times. Even within 10 weeks of an epidemic, valuations vary widely between countries, ranging from 0.1 to 5.1 per cent. the actual H1N1 case death rate is much lower when healthcare staff have the opportunity to view case documentation and evaluate cases, at 0.02%.
`It`s not complacency ,` he said. But it could be an antidote to alarm bells in some countries reporting extremely high death rates.
Hidden death
While the calculation may lead to exaggerated death rates, another factor can make death rates undervalued.
This is a problem in cases of undetected but new coronavirus deaths. This happens when the health care system is overwhelmed and even those with severe illnesses are not taken to hospital for testing and treatment. This is simply because there is no capacity to do so.
At Nembro (Nembro), a small town in Lombardy, Italy, only 31 people have officially died of the new crown virus. But a study has found that more people may have died the new crown virus. This is because the total death rate this year (not only the death rate for the new crown virus, but also the death rate for all reasons) is four times higher than the same period last year. Usually in the first half of the year, there are about 35 people in Nembro death .158 registered this yea
A spike in death is presumably due to untested and undiagnosed patients with new coronavirus.
The number of beds available may also play a role, as countries with weaker health-care capacity may have to start deciding more quickly which new crown patients will be the focus of treatment. As symptomatic people stay away from the medical system, this may result in more patients with new crowns dying in the community but not being tested (and statistically).
How old is the age factor?
Besides the different identification criteria of the new crown death and the number of people not tested, there are other factors that affect the epidemic situation in various countries.
Italian doctors suggest that the age characteristics of a country are one factor. In 2019, nearly a quarter of Italians were over 65, compared with only 11% in China. By mid-March, Italy had a total mortality rate of 7.2 per cent, much higher than China`s death rate of 2.3 per cent in the comparable phase of the epidemic. Researchers at the University of San Diego (Istituto Superiore di Sanita in Rome) in Rome pointed out that the death rates in China and Italy were comparable from zero to 69.
But among the oldest patients, italy and china were significantly different. In Italy, the death rate in the 70-79 age group was 12.8 per cent, compared with 8 per cent in China. This difference is more pronounced in the age group over 80 years :20.2 per cent in Italy and 14.8 per cent in China. The researchers point out that the cause of the difference remains a mystery.
Heineken suspects that one of the causes of Italy`s high death rate may be unrelated to the virus itself but to bacteria. Italy has the highest number of death due to antibiotic resistance in EU countries. As a matter of fact, Italy has one third of the total number of death in the EU due to antibiotic resistance. Although antibiotics are powerless against viruses, viral infections often pave the way for complications such as secondary infections or bacterial pneumonia. If, in that case, the bacteria are resistant and can not be treated with antibiotics, it may be the cause of death, not the virus itself.
"It`s very important part of the whole story, and it`s especially common among older people ," Heanegan said. "
As with age, people`s overall health status is also considered another important factor, and people with potential health problems are more vulnerable to new crown virus. But this may work, but it does not explain why some countries report more new coronavirus death than others: Italy, for example, has been ranked among the world`s healthiest countries and has a longer healthy life expectancy than China.
For some time to come, knowing exactly how lethal the new crown virus is will remain a challenge. Detection of new crown patients in many countries around the world is too slow, leading to the possibility that real data on the number of death caused by the new crown virus may never be available.
as time goes by, clinicians can finally look at the case records and find out the coronavirus patient death. the statistical accuracy of the new coronavirus death rate may be improved.
For now, the hospital is full of severe patients inside and outside, doctors and nurse are working overtime to take care of them, and careful clinical analysis will have to be shelved.
