It all started on December 31 when the World Health Organization (WHO) confirmed the first case of coronavirus in China. Since then, there are more than 24,500 confirmed cases (more than 24,300 in the Asian country alone) and 493 deaths. And the numbers keep rising at times.
The epidemic, caused by a virus such as severe acute respiratory syndrome (SARS) or the Middle East coronavirus (MERS-CoV), has also had the ability to pass from animals to humans.
It is compared to the influenza virus, which occurs in the form of a seasonal epidemic every winter in our hemisphere, an old acquaintance that has been monitored for a long time. However, we still know very little about the new coronavirus. Amparo Larrauri, who works in the Flu Surveillance Group and is the group leader of the CIBERESP at the National Center for Epidemiology-ISCIII, analyzes the differences between the two viruses.
One of the things that worries the most is the lethality rate of the virus …
Of course, knowing how many people die among those who have contracted the disease gives an idea of its severity. But this is one of the most difficult things to establish. It is a ratio between a numerator (number of deaths caused by that virus) and a denominator (number of cases infected by that virus), and that data changes every day.
It can go towards a higher lethality rate if in that ratio the numerator (the deaths) increases with the days. But it can also go to a lower severity, if what increases more is the denominator (cases that do not end in deaths).
There are currently about 90,000 cases under investigation that are suspicious in China. Therefore it is very likely that the denominator increases greatly and the lethality rate drops.
Right now, that lethality rate has a value between 11 and 14%, can it be compared with other epidemics?
These are just estimates, it is impossible to know the rate exactly yet. It must be taken into account that this 14% is taken from one of the most recent studies, but it has only taken into account the deaths produced among the most serious hospitalized cases.
In principle, what we know is that it would be quite similar to what happened with the SARS in 2003, which had a lethality rate of 10%, while in the MERS-CoV it was higher, of 32%. For its part, the flu has between 10 and 14% lethality in severe hospitalized cases, which would go down to 6-7% if we counted hospitalization figures without these serious criteria.
And do we know the ability of the virus to be transmitted among the entire population?
It depends on how it is pathogenic and transmissible, and this can also change when more data is known. Every day more groupings of cases are studied to see how many secondary episodes have left from a primary one, which is called Ro.
While this coronavirus has a Ro of approximately 2.2 (it can reach between 2 and 4), in the SARS we had quite similar figures: around 3. However, the MERS-CoV, which was much more pathogenic, had – and has, because it has not disappeared – a much lower transmissibility; Like that of the flu, which is around 1.1-1.2.
How are control measures being applied?
At the moment, the coronavirus causes 17% of serious cases but, once again, these are only estimates. It is presupposed an ability to cause similar severity or somewhat less than SARS.
It should be clarified that the SARS epidemic was completely controlled and there are currently no viruses in humans. It lasted 8 months, 8,000 cases were confirmed worldwide and there were 700 dead. Now with the coronavirus we have been a little over a month, there are more than 24,500 cases confirmed and almost 500 deaths, with just 200 cases outside of China (only 24 cases confirmed in the European Union).
It is that balance between virus pathogenicity and transmission capacity that determines how it will expand, but above all, how we will be able to apply these measures.
Do you remember any previous scenario like the one we have seen these days in the Asian country?
In China they are doing an incredible thing, never seen. I think the SARS epidemic has taught them a lot and it is logical that other guidelines be taken and lessons learned. The fact that China saw that it was a complicated situation and took measures to prevent further spread is exceptional. On the other hand, it may also be the only country in which such measures could have been taken.
What is clear is that since the first case was confirmed on December 31 until now there has been a great display of information that on other occasions there has not been and, above all, a very fast action: a case is confirmed, Already a week we already have the genome identified. That is a success of public health coordination around the world.
How can the alarm level of the epidemic be assessed?
It is not a matter of alarming or giving it little importance. If a case comes, surveillance systems have to function strictly, identify potential contacts as soon as possible and follow up.
At this time the risk of continuing to spread the disease in the world, especially in China, is high. The risk of identifying confirmed cases in Europe is relatively medium, as many of them can still be imported. Now, the risk that they occur in Europe if the disease control and prevention conditions are properly followed is low.
For example, in Spain, if the conditions established in the protocols agreed by the type of alert are strictly applied and all the autonomous communities and the emergency center of the Ministry of Health – coordinator of the entire outbreak – are involved, the risk of Keep transmitting the virus is low.
What about confirmed cases that are not serious? When is your infectivity period over?
Any suspected or confirmed case is followed for 14 days for prevention. In addition, coronavirus appears to be infectious before symptoms begin, although it has not yet been established safely. What is alarming people occurs in almost all viruses, such as influenza, which is transmitted 24 to 48 hours before symptoms and up to 4-5 days later; or measles virus, which is transmitted 4 days before having the rash.
The capacity to contain an epidemic is linked to the pathogenic capacity of the agent, that is, to the ability of all infected to manifest symptoms. Because the more cases that can be identified, the more contact measures we can put in and define the situation. If not, there will be more people who do not even go to the doctor and are transmitting it. That is why it is now claimed that the measures have to be very strict.
In addition, these viruses also have the ability to generate large transmitters or supercontailers. It is not exclusive to the coronavirus, with the SARS on a transoceanic flight more than 160 infections were established.
Are we inflating the risk of coronavirus with respect to the flu?
There are more than 25,000 confirmed cases of coronavirus and 493 deaths. That’s what you get. But it is logical that people compare with the closest, such as seasonal flu. The problem is that the general view of influenza from the bulk of the population is wrong, it is not a mild disease.
In our weekly flu surveillance report You can see how in most cases it produces mild symptoms. However, there are other truly serious cases that lead to complications that cause death every winter season (between 6,000 and 15,000).
These deaths are concentrated in people who are at high risk of complications. And among severe cases, 80% had underlying disease, and among deaths from influenza, more than 90% had underlying disease. Likewise, it is difficult to estimate the number of deaths caused by the flu since there are many older people who die in their homes and do not go to the hospital, as is also happening in China.
What worries the coronavirus epidemiologists most?
What most worries about the coronavirus is not the number of deaths, but in just one month we have 25,000 cases. This gives you the idea that the transmissibility is quite large. And maybe the problem is not gravity, but the possible collapse of the health system.
In China they have made a hospital with 2,000 beds in eight days, and they could do it again, but it would be difficult in another country.
Are we going to reach a pandemic with this virus?
A pandemic happens when a certain agent is distributed worldwide and there is a sustained transmission. Right now with the coronavirus is not the case, but you can not predict what will happen. Since the 2009 H1N1 flu there have been none.
In Europe there are 24 cases, but there is no sustained transmission. There is a case in France that has occurred through a family group and, of the 12 cases in Germany, at least 6 are also related.
The key is in containment. As long as the virus does not have a brutal interhuman transmission capacity and we can contain it, it will happen as with the SARS, which was a major health problem but was controlled. In fact, there is no longer this virus in humans.
Will there be more cases in Spain?
Possibly, it falls within the expected. The important thing is to be able to explain its origin and control it. That gives peace of mind, although it is normal for health systems and society to be stressed in such a situation. The point of unpredictability and novelty are the points that mark an epidemic.