COVID-19 and flu compared: which is more dangerous?

COVID-19 and flu compared: which is more dangerous?

Opinions differ on the contact restrictions and the severity of the disease COVID-19 caused by the SARS-CoV-2 coronavirus . Both the general public and experts are discussing how to deal appropriately with the current coronavirus pandemic. The annual flu (influenza), which also causes numerous deaths, is often used as a comparison. In this article, you can read to what extent you can compare the two diseases, what they have in common and what profound differences separate them.

How is it calculated how many people have died from COVID-19 or the flu?

The number of deaths from each is often compared when comparing the dangerousness of the two diseases. However, the calculation of these numbers presents a significant difficulty.

The number of people who die each year from the flu is described by what is known as  excess mortality”. It indicates how many more people have died in a given period compared to the average death rate in previous years.

During the 2017/2018 flu season, we had the highest rate of excess mortality from the flu in recent years. The recorded fluctuations in mortality generally range from mid-December to mid-March of the following year.

The number of people who have died from the disease COVID-19 is currently being determined primarily based on registration numbers. However, information on excess mortality also shows an increased number of deaths.

The current figures are reported by the German Robert Koch Institute (RKI) and the American Johns Hopkins University (JHU), among others. However, the two institutions do not present identical case numbers.

 

Why do the RKI and Johns Hopkins University give different numbers?

The difference comes from the fact that the RKI only includes officially reported cases in the statistics. At the same time, Johns Hopkins University supplements the reported formal data with the help of models.

It takes time for positive test results to be reported to the RKI. The positive test is first reported to the local health department and then to the relevant state government, which transmits the data to the RKI. This reporting process can take up to two days. In addition, the data at the RKI is only updated once a day, and the data can be received by the RKI late, for example, due to overworked health authorities.

Johns Hopkins University bypasses this queue by supplementing the data with models and other sources. For example, the World Health Organization (WHO) and publications by local authorities play a role here.

How many people die from the flu each year?

During the 2017/18 flu season, around 25,000 more people died in Germany than died on average within a period of the same length without a flu outbreak (excess mortality). In contrast, only 1,674 people have died from the flu, which has been proven, i.e. confirmed with the help of laboratory tests. However, the 25,000 deaths can be attributed to the flu because there is no other valid reason for the increase in deaths at the time. So, the figure is calculated using inference.

The annual number of flu deaths calculated using the excess mortality usually ranges from several hundred deaths to around 20,000 deaths.

In some years, there has been no evidence of excess mortality. Although laboratory-confirmed influenza deaths have also been found in these years, they do not result in increased deaths compared to the average number from months without influenza.

In the 2020/21 flu season, the flu wave was shallow – probably due to the effective coronavirus protection measures. As of May 21, 2021, only 564 confirmed cases of influenza were reported, and 16 deaths can be traced back to the flu with certainty.

 

Excess mortality (excess mortality) with a view to coronavirus deaths

As an alternative calculation method, however, the latest figures on excess mortality were also used to determine deaths from COVID-19. However, since this method is very imprecise, there are differences in these values ​​compared to the reported deaths. At the end of March 2020, the total number of people who died in Germany each month increased slightly. However, the flu wave was considered to have ended in mid-March, so deaths should not increase but decrease. The coronavirus pandemic could, therefore, explain this excess mortality.

The upward deviation was most significant in the 15th calendar week (April 6 to 12th, 2020). Twenty thousand four hundred fifty-nine people died in Germany this week. From 2016 to 2019, there was an average of 17,908 deaths in the 15th calendar week. This week, the excess mortality was 2,551 people. 1.2

The number of deaths has been declining since mid-April. While an increase in excess mortality in August can probably be attributed to the heat wave, about five per cent more deaths were reported for the 43rd calendar week (19th to 25th October 2020) than in previous years, which is reflected in the confirmed deaths of SARS-CoV-2 can probably be traced back to COVID-19. Throughout 2020, excess mortality continued to rise, which was also attributed to COVID-19. While the excess mortality in October was initially 5 per cent above the average of previous years, it was 12 per cent in November and 32 per cent in December. 1.2

Subsequently, both excess mortality and reported deaths from COVID-19 declined somewhat in early 2021 (January deaths were 25 per cent above the average for previous years). While the number of deaths in February and March was below the average of prior years, it has usually been slightly higher since April. 1.2

According to EuroMOMO, a portal that has been collating deaths in 24 EU countries for years, a total of 100,000 more people died in the EU between mid-March and mid-April 2020 than on average in previous years. Of these, around 95,000 cases belong to the over-65 age group. Here, a significant increase in deaths can also be seen again from calendar week 43. A further increase can also be seen here in 2020/21. 3

However, the figures on excess mortality can only be presented with a time lag, which is why the current month’s data are unavailable.

 

Are the flu death numbers comparable to those of the coronavirus pandemic?

Selbst wenn man zum Vergleich der Todeszahl von Grippe und COVID-19 keine unterschiedlichen Berechnungsmethoden heranzieht, sondern in beiden Fällen die Übersterblichkeit betrachtet, sind diese Zahlen nur bedingt vergleichbar. Denn wie bereits erklärt, ist die Übersterblichkeit kein genauer Wert, da sie keine anderen Einflussfaktoren mit einbezieht. Es wird lediglich berechnet, wie viele Menschen mehr verstorben sind, jedoch nicht aus welchem Grund. Ohne eine Aussage über die Ursachen und Zusammenhänge treffen zu können, ist auch ein reiner Vergleich der Zahlen nicht aussagekräftig.

Was die Zahlen verfälschen könnte, lesen Sie im Folgenden.

 

Wodurch werden die Todeszahlen möglicherweise verfälscht?

Die Todeszahlen können in Bezug auf COVID-19 möglicherweise durch folgende Aspekte beeinflusst werden:

1. Die Übersterblichkeit lässt keine genaue Differenzierung zwischen direkten Krankheitsfolgen des Virus und indirekten Folgen, beispielsweise durch den Ausfall von Kontrollterminen oder Operationen, zu:

  • Menschen mit schweren Erkrankungen gehen derzeit möglicherweise gar nicht oder später in eine Arztpraxis, da sie sich vor einer Ansteckung im Wartezimmer fürchten. Das könnte bewirken, dass schwer kranke Menschen durch das Ausbleiben eines Arztbesuchs nicht die Hilfe bekommen, die sie eigentlich benötigen, und vorzeitig ihrer Erkrankung erliegen.
  • Auch könnte das Ausfallen von Operationen zu einer erhöhten Sterblichkeit führen, die nur indirekt mit dem neuartigen Coronavirus zusammenhängt.
  • Durch das Fehlen von Sozialkontakten und die möglicherweise schlechtere Versorgung psychisch kranker Menschen in Zeiten der Corona-Pandemie könnten zudem die Suizidraten steigen.

2. Selbst bei einer nachgewiesenen COVID-19-Erkrankung sind Todeszahlen mitunter schwer zu bestimmen:

  • Die Exzess-Mortalität kann nicht differenzieren, ob ein Mensch tatsächlich an der Erkrankung verstirbt oder an anderen, von dem Virus unabhängigen Erkrankungen. So stellt sich doch die Frage, ob eine Person, die positiv auf das Coronavirus getestet wurde und nach einem Schlaganfall oder einem Herzinfarkt verstirbt, letztendlich an diesem oder an COVID-19 verstorben ist. Aus diesem Grund könnte die Anzahl der an COVID-19 verstorbenen Menschen zu hoch angesetzt werden.
  • Außerdem versterben die Menschen nicht direkt nach ihrer Infektion an der Krankheit, sondern meistens Wochen danach. Aus diesem Grund können einige Betroffene, die infiziert, aber (noch) nicht gestorben sind, aktuell noch gar nicht korrekt in die Statistik einfließen.
  • Des Weiteren könnten auch einige infizierte Menschen verstorben sein, bei denen kein Nachweis des Coronavirus erfolgte. Das würde bewirken, dass es eine Dunkelziffer an Personen gäbe, die unbekannterweise an dem Virus verstorben sind. So sind beispielsweise während der ersten Welle in Italien aufgrund fehlender Behandlungskapazitäten einige Menschen verstorben, ohne behandelt oder getestet worden zu sein. Diese Todesfälle beeinflussen zwar nicht die Übersterblichkeit, lassen aber die Statistik der COVID-19-Verstorbenen zu niedrig erscheinen.

3. Auf der anderen Seite können die allgemeinen Todeszahlen durch indirekte Folgen auch gesenkt werden:

  • So könnte durch das verminderte Reisen die Anzahl der Autounfälle abnehmen.
  • Außerdem soll die verbesserte Luftqualität durch das verminderte Reisen circa 11.000 frühzeitige Todesfälle in Europa verhindern. Demnach würde es eine kleinere Übersterblichkeit geben, obwohl viele Menschen an COVID-19 verstorben sind.
  • Durch die erhöhten Schutzmaßnahmen und die stärkere Sensibilisierung der Bevölkerung für Hygienemaßnahmen ist die Zahl der Grippe-Toten niedriger ausgefallen.

Durch eine Verschiebung der Altersstruktur sind darüber hinaus Abweichungen in beide Richtungen möglich.

Due to the named disruptive factors that influence the excess mortality figures, it is currently not possible to name a reliable number of deaths in this way. This makes it much more difficult to compare the number of deaths – and therefore mortality – with those of the flu seasons of recent years.

What are the differences and similarities between the two diseases?

The incubation period describes the period from infection with a virus to the onset of symptoms of the disease. For the flu it is on average one to four days. For COVID-19, on average it is slightly longer, namely five to six days. As a result, people who get COVID-19 become symptomatic later than people who get the flu. They may stay home later and potentially infect more people during the time when they don’t notice symptoms. Additionally, many people who become ill with COVID-19 have no symptoms at all, which could encourage more careless behavior.

The risk groups for severe disease are very similar for both diseases. Older people with previous illnesses such as  diabetes  mellitus or chronic lung diseases are primarily affected. According to the current status, 86 percent of those who died from COVID-19 in Germany were 70 years old or older; the mean age was 82 years.4

In contrast to the flu, children and pregnant women are not among the risk groups for a severe course of COVID-19. However, there are also risks for these two groups, and the effects on these groups have not yet been sufficiently clarified.

You can read about how the symptoms of COVID-19 differ from those of the flu here.

What is more dangerous about COVID-19 than the flu?

When comparing the two diseases, one should not only look at the total number of deaths, but also the  infection mortality,  i.e. the proportion of infected people who die from the disease. For both the flu and COVID-19, this number depends heavily on the population group, as in both cases it is significantly higher in risk groups. For Corona, mortality is estimated at an average of 0.5 to 1 percent, for influenza it is 0.05 to 0.1 percent. So out of 10,000 people infected, an average of 50 to 100 people die from a corona infection, and only 5 to 10 from the flu.

A corona infection can also  cause  long-lasting long- term consequences  , which are now summarized under the term Long COVID  and affect numerous infected people. Although long-term effects are possible after the flu, they occur less frequently and in a less varied manner.

While the flu only  occurs seasonally  and the spread usually subsides as temperatures rise, this is not the case with SARS-CoV-2.

In order to keep the number of infections with the coronavirus as low as possible,  extensive protective measures were  taken, which made it possible to massively reduce the number of cases. It is precisely these successful effects of contact restrictions that can also cause the virus to be underestimated. Ultimately, only the number of people affected and deaths that occur with contact restrictions is known. It is unclear how much higher the number would have risen without contact restrictions.

There are also other factors that differentiate COVID-19 from influenza.

 

Lack of immunity in the population and higher infection rates

At the beginning of the pandemic , a crucial difference between the two diseases was   the availability of a vaccine. While a new vaccine is made available for the flu every year, there was initially no vaccine against SARS-CoV-2 available. Members of risk groups therefore lacked an effective way to protect themselves from the disease. Now that there are sufficient vaccines available in Germany and the majority of the population has been vaccinated, there is at least better protection for those who are immunized than at the beginning of the pandemic. However, new virus variants resulting from mutations can reduce the effectiveness of protection.

In addition, the flu is not a new disease for humanity, but one that recurs every year. Although the virus is very versatile, people who were infected with the flu in the previous year can be protected against the virus in the following year if it has not changed too much. If the virus has only changed slightly in a year compared to the previous year, then the flu wave will be significantly milder. This is due to the so-called “basic immunity” of the population, which describes how many people are immune to the disease, i.e. already protected.

SARS-CoV-2 is a new virus for which there is no basic immunity in the population. This allows the virus to achieve a higher infection rate and thus spread quickly and widely.

A measure of this infection rate is the  reproduction number  R, more precisely the  basic reproduction number R0.  It tells you how many people an infected person infects on average – even if no restrictive measures apply. For the flu, R0 is given as 1 to 2 depending on the season, with an average of around 1.3. According to current knowledge, the basic reproduction number of the original type of SARS-CoV-2 is around 2.8 to 3.8 – and even higher for new virus variants.

Lack of treatment options

Another difference can be found in the treatment options for the two diseases. For annual influenza, medications are available that, for example, intervene in the virus cycle. They are intended to prevent the virus from being released from the cell it has infected into the human organism. This can shorten the duration of the illness and alleviate the symptoms.

Research into medications and therapies continues to be carried out at high speed to combat the novel coronavirus. However, there is currently no drug that can reliably help against SARS-CoV-2. Therefore, often only the symptoms and consequences of the disease can be treated, but not the disease itself. The body has to fight the virus itself, which is a challenge, especially for the immune system of older or already sick people.

In the treatment of influenza, the focus is also on reducing the symptoms, but the medications already mentioned are also available.

Conclusion: What is more dangerous – COVID-19 or the flu?

The problems listed show that COVID-19 is a disease that should be considered. The flu is also a severe illness. Based on current knowledge, it can be assumed that COVID-19 is more dangerous than the flu for many reasons.

One should not only compare the number of deaths. On the one hand, this is because the latest and, above all, the final figures for the coronavirus pandemic are not yet available. On the other hand, the excess mortality cannot provide any precise information as to whether all additional deaths due to the disease COVID-19 are indebted or whether they have different causes. However, numerous other factors show that coronavirus cannot be equated with a flu epidemic, as COVID-19 is many times more contagious and deadly – and this is despite protective measures that are not usually taken during seasonal flu.

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