Much more deadly. Mortality from seasonal flu is not easy to estimate, but experts from the Grippenet.ch network estimate it around 0.1 to 0.2%. The rate is ten times lower when looking at direct mortality alone, that is, people whose deaths are directly related to the flu.
Covid-19 for its part has a direct mortality estimated between 1% and 3%, according to sources. The Chinese Center for Disease Control (CDC) reports mortality of 2.3%, which varies greatly between the outbreak of Hubei (2.9%) and the rest of China (0.4%).
In any case, the case fatality rate in China has evolved over the weeks, gradually approaching 1%. It is also mortality in South Korea (0.7%), and a good candidate for the low range. The rising range is more likely to be sought from Italy, with a mortality of almost 4%, which is explained at least in part by its elderly population.
In the state of knowledge, the new coronavirus is therefore much more deadly than the seasonal flu, by a factor of 10 to 100. If it were necessary to find a more suitable point of comparison, Covid-19 would be closer to the influenza pandemic from 1918 (“Spanish” flu).
This fatality rate can be overestimated: current diagnostic tests (by sequencing the viral genome) only allow symptomatic cases, managed by the health system. The first serological tests, which assess the number of infections in a representative sample of the population, are starting to be available. They will make it possible to specify the real mortality rate in the weeks or months to come.
Contagiousness. Epidemiological estimates give a basic reproduction rate (R0) of the new coronavirus between 2 and 3. In other words, a person infected with Covid-19 tends to infect 2 or 3 others in turn. It’s more than seasonal flu, including the R0 is around 1.5. Epidemiologists see this as a sign of similar contagion potential.
The mode of contagion – by contact and droplets – is the same for both types of virus.
Transmission of the new coronavirus from faeces cannot be ruled out, but this risk has not yet been confirmed and is more likely to affect countries with low levels of development.
Ditto for contagion via inert surfaces: the virus can undoubtedly remain there and active for a few hours or more (depending on the temperature and humidity conditions), like other coronaviruses, but the actual risk of transmission not known.
Contagious + lethal = problem. Epidemiologically, it is the combination of a contagious virus and the lethal that represents the greatest public health challenge. This is the case with the Covid-19 epidemic.
This does not mean that the individual risk is necessarily high: it depends very much on the state of health and age. For people under 60 and not having a chronic disease, it is a priori very low. For the vulnerable, the risk is much more worrying (to see further).
But from a public health point of view, the major risk is that of saturation of the health system, which would prevent the proper treatment of infected patients, for lack of beds, equipment or available health personnel. This is what happened in Wuhan, and seems to be taking place in some Italian hospitals.
If healthcare workers start to be affected en masse, in the hospital or on an outpatient basis, the entire healthcare system can be destabilized. As the WHO recently noted, economic plans that have hit western hospital systems in recent years exacerbate this risk. Hospital accommodation has often been cut to the bone.
In these conditions, the individual prevention measures are intended to protect the most vulnerable, but also to avoid a more general impact of the epidemic on our societies, in health, economic and political terms. The effectiveness of these measures is counterintuitive: due to the exponential progression of the epidemic, any measure followed at the community level can result in a severe limitation of the total number of cases.
Same individual prevention measures. The individual prevention measures are the same as for any respiratory infection, flu included:
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wash your hands regularly,
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avoid close contact with people showing potential signs of infection,
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avoid kissing or shaking hands to greet each other,
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cough and sneeze into disposable tissues, or failing that into his elbow,
The OFSP has opened an information line, which can be reached on +41 58 463 00 00, which is now open 24 hours a day.
Similar symptoms. The first symptoms of coronavirus are suggestive of an influenza-like illness: the infection is generally manifested by fatigue and fever (88%), general malaise, quickly followed by a dry cough (68%). The picture can then progress to pneumonia, with respiratory distress which may justify the use of artificial respiration.
On the other hand, a runny nose is not a typical symptom of Covid-19, which is definitely an infection of the lower respiratory tract (bronchi).
There is every reason to believe that people who are infected but do not have (or not yet have) symptoms are rarely contagious.
The future of patients. Still according to Chinese data, in infected patients:
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81% present or presented a benign picture;
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14% are in serious condition, such as pneumonia and respiratory failure;
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5% are in critical condition, with major respiratory failure (acute respiratory distress syndrome), septic shock, multiple organ failure.
A recent study in Wuhan finds that half of critically ill patients die from the disease.
These data are crucial for preparing the health response:
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mild conditions can be managed on an outpatient basis (home and city care),
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serious conditions require hospitalization, for example in dedicated areas of infectiology or pneumology,
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critical conditions require intensive care (assisted ventilation, even extracorporeal oxygenation).
The impact of age. It is one of the key factors of vulnerability to Covid-19, like the flu. Also according to data from the Chinese CDC:
In other words, the lethality is virtually zero in young people and adolescents, very low between 30 and 50 years, and begins to become important beyond.
Beware of overinterpretations: being (relatively) young and in good health is no guarantee of immunity. Chinese data estimate the proportion of patients who died without any other identified disease at 0.9%.
Dr. Bruce Aylward, who led the WHO mission to China, reported on Tuesday (February 25th) that Chinese doctors have faced severe cases in people who are thought to be less vulnerable.
Children spared. This is a major difference from the flu: the coronavirus infects – and affects – very little children. To date, the youngest patient infected with Covid-19 was 10 years old. Mortality among people under the age of 20 is virtually zero.
This is great news from an epidemiological point of view, as children are a key vector for the spread of infectious diseases.
We now know that children are not better protected than adults against the virus: their infection rate is similar, but they tend to have only mild or imperceptible symptoms.
Seasonality. The flu virus – or rather the virus, as strains vary – circulates every year in temperate zones, causing a winter pandemic. It is not impossible that Covid-19 will experience a similar fate, with a reflux in spring and a return in autumn. Only the future can tell.
The proven seasonality of the flu, on the other hand, is good news concerning the chances of containing Covid-19: the peak of the influenza pandemic having been reached during the first week of February in Switzerland, it will be easier and easier to detect cases. infection with the new coronavirus.
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