Newsletter 8,June 27, 2020 Rational measures against CoVid-19. "Current policy is not so bad."

The Dutch policy against Corona (Covid-19), like that of most other countries, is aimed at a strict Lock-down and then a slow relaxation of measures aimed at controlling the infection rate among the population. One of the most important measures is to keep a distance from each other.

Now that it looks as if we are keeping the coronavirus at bay and the infection rate among the population is clearly decreasing, criticism of the measures is (not unexpectedly) increasing. In the Netherlands, this criticism is led by Maurice de Hond, one of the most famous "pollster" in the country, who, among other things, keeps a weekly record of the political preferences in the nation. The critics first of all criticize the issuing of the Lock-down measure. They think this is unwise because the Lock-down has very serious economic consequences. "Is the measure no worse than evil".

When the Netherlands and other European countries were confronted with a large number of Covid-19 patients, the immediate reaction was: the spread of the virus must be stopped. The reason for this was that it was clear from the beginning that it would be impossible for all Covid-19 patients who would have to be admitted to the hospital because of the seriousness of the disease, there was just no plce.  Without Lock-down there would be no beds for those and certainly no ICU beds.

A Lock-down would mean, was the expectation, that there would be a very rapid increase in the number of patients, but that after four weeks there would be a sharp decline. After all, if people were forced to stay at home, all housemates would be infected in those homes where an infected person would stay from the outset.

In essence, Lock-down means deliberately allowing the number of infected persons to increase very quickly and violently, after which a sharp decrease would occur four weeks later (twice the maximum incubation period). Indeed, in most cases the peak of the number of infections was reached after four weeks. The rapid decline thereafter was less rapid than could be predicted. The cause of this was the lack of protective clothing for the care and treated staff. As a result, the disease was not stopped in hospitals and care institutions.

(If a next Lock-down would be needed, with a prepared society one can already start to relax 10 days).

Those who claim that Lock-down was not necessary should realize that there would have been many more victims and that many patients could not have been admitted due to a shortage of beds. Had Lock-down not been implemented, the pandemic could have spread slowly. Society would then have had to deal with large numbers of patients for a very long time. This is reflected in the creeping increase in the number of infections in countries where an adequate Lock-down was not implemented. Theoretically,it would have been much quicker to master the epidemic if everyone had stayed 1.5 m apart from each other from the start of the epidemic, not only outdoors but also inside the household. In that case, the peak would have been seen after only two weeks and all measures could have been relaxed from then on.  Of course, a 1.5 m social distance within households was not feasible either.

Without Lock-down we would not have been able to control the epidemic. Moreover, containment of the spread of the infection reduced the chance that a mutation would have made the virus more virulent and contagious. Releasing the virus could have led to an increase in the infection rate (R> 2-3).

This does not alter the fact that it was unwise to introduce a Lock-down in areas where a Lock-down was impossible. In countries where many inhabitants and many migrant workers are very poorly housed, it is not possible to implement a Lock-down.

Maurice de Hond's claim that Lock-down was not necessary because the virus spread only with difficulty is therefore not correct.

Some people claim that the 1.50 m social distance is nonsense. They go back to literature from the 1930s. At that time they rightly wondered: how contagious is a patient with an infection. How does the microorganism spread when someone has a cold or has the flu? At that time, people were especially interested in the spread of tuberculosis.

It was then discovered that people produce droplets and droplet nuclei (very small droplets: aerosols) around them by coughing, sneezing, talking. Most of the particles in the environment are droplets. These droplets generally do not spread further than 1-2 meters from the coughing person. The aerosols can spread further. They are often dried droplets. For tuberculosis, it has been shown that such a droplet core (aerosol) may only contain one tubercle bacterium and that the aerosol can penetrate into the lung vesicles and cause TB.  For Covid-19 patients this means that most Covid-19 viruses are in the droplets and a much smaller number in the droplet nuclei. Moreover, these aerosols have been suspended in the air for a longer period of time and have dried up, which means that the protein mantle of the virus may have been denatured during that time. Proteins can denature quickly and are then no longer able to adhere to specific receptors in the mucous membrane. As a result, the virus can no longer penetrate the mucous membrane.

Droplets are therefore a much more important dispersal vehicle than aerosols. Droplets are often trapped in the nose or trachea and can then be removed without making humans sick. The aerosols pass through the nose and bronchi and reach the lungs directly. But for the Covid-19 it is true that there are receptors for the virus in the airways. In almost all cases Covid-19 starts in the upper respiratory tract. The infection then spreads further to the lungs from the upper respiratory tract. 

We don't know yet how the Covid-19 infection originates, but let's use our common sense.

So it's not that we need aerosols to infect. Infected people produce many more drops than aerosols (droplet nuclei). Droplets are more dangerous because they contain many more active virusparticles. And possibly aerosols don't even contain active viruses anymore or their number is just too low to cause an infection.

Outdoors, one gets rarely infected, the critics are right. Indoors, the value of air treatment is of course very important. With good filters in air-conditioning systems a lot can be solved.

The question whether passengers of cruise ships were infected by air conditioning was raised already four months ago. If that is true owners of the cruise ships are still awaiting heavy court procedure. But the chance cannot dismissed, that the very poor living conditions of the crew on such ships are the cause of infections. The number of employees on those ships is almost as high as the number of passengers. While the passengers are bathed in opulence, the crew is housed in very, very small cabins. It happens that crew members have to use the bed of a colleague who is on another shift.

In conclusion: a pandemic of respiratory tract infections should generally be fought with a Lock-down. The disease spreads through the air. Keeping a distance from each other is essential. Air treatment, testing and source detection from the start ensures that the next time the epidemic remains under control.

Prof Dr Jan Verhoef Em Professor in Medical Microbiology and Infectious diseases UMCUtrechtFellow European Society for Clinical Microbiology and Infectious Diseases