It is possible to reactivate our economy with Covid-19: part II

We conducted a simulation to the proposal described in my previous entry. Result: if at least 62 percent of the country's inhabitants wear masks and facemasks, transmission of covid-19 can be stopped, without confinement of the entire population and with minors distancing restrictions.

We also wanted to test whether the same result could be achieved by randomized diagnostic tests performed daily.

Following ideas and simulations from Paul Romer, 2018 Nobel Prize in Economics, we calculated just that amount described above, something that should be very useful for any leader in a city or country: how many tests per day should be done to stop the infection, to achieve R0 <1? For how long should they be carried out?

Result: a million tests are required daily in Colombia (2 percent of the population), for at least 300 continuous days.

If this testing initiative starts in April 27 in Colombia, and we assume that at that time R0 = 1,2[1], it is required to randomly carry out a million diagnostic tests daily to achieve it

With the help of the ECSIM team of experts led by Diego Gómez, a simulation was carried out for them based on the SIR model, which ratified the above, and allowed us to find that it would take at least 300 continuous days to achieve it.

This simulation was carried out for the Medellin Metropolitan Area, but if it is scaled throughout the country, the results are similar: 2% of the population daily and +300 days. The change in the model is seen in the following graph, when the number of daily tests is increased to reach 2% of the population[2].

Following that line of thought, I created a very simple tool that allows each city’s Mayor and his team to know if their objective is achievable and what the monetary values involved would be. Both for PCR-type tests, as well as for other technology that may be authorized in the future by the country's health authorities.

In this link  find a simple model in a spreadsheet. I invite anyone to use it, correct it or extend it, and determine for their situation an approach to the diagnostic tests that must be implemented.

It is clear that the feasibility of carrying out these tests is very small. Not only for the costs involved, but also for the logistics required to do them throughout the country.

Today every country is trying to increase, with huge difficult, the total number of diagnostic tests for day. I do not believe it is feasible to reach a million a day. Even more without counting on the monetary resources and logistical capacities necessary to create and maintain all the epidemiological fences in place, throughout the country, generated from their daily results.

If this strategy does not start immediately after finishing the confinement, it is very likely that R0 will go up in value again. Being different from 1.2, the number of tests will grow significantly, making this strategy even more improbable (it can be verified in the spreadsheet).

In each locality, each metropolitan city (metropolitan areas, for example), there must be a different R0 value, the diagnostic test strategies must be different for each city or village, and not a single measure for the entire country.

The Isolation Lottery

It is interesting to see that Paul Romer simulated a program of random confinement of a segment of the population, but without the use of diagnostic tests, and the results obtained were very similar to those obtained when massive random diagnostic tests were used!

In that case, there would be something like the quarantine raffle, which assigns a percentage of the population that must go into isolation for two weeks each day. This process will be made by the government of which a percentage, for example 3 percent of the numbers national IDs declared “winners”, must immediately be isolated for 14 days, whether or not it is known that these people are infected.

Each citizen will be selected several times on average, and each time that person would have to go into quarantine. The proposal would work at least equal to that of diagnostic tests, but unlike this latter possibility, not only will it save millions of dollars, but it will also be more feasible to implement in terms of required logistics.

However, it is clear that it would be very difficult to obtain citizen’s support for a public health policy based only on random values and where it is almost impossible to explain to each citizen why they must stop working for two weeks, time and time again, when it is their turn, despite being apparently without the virus.

An additional proposal to the previous one, would be to combine the raffle with some diagnostic tests and allow those who are chosen to be able to take on their own diagnostic tests; which if presenting negative result, that person will be able to avoid isolation. However, this would be a clear case of promoting inequality, since only certain people could finance their tests. If the state were to pay for them all, we would return to the case of massive random diagnostic tests and the raffle would not make sense.

In any scenario, the logistics to force the periods 14 days of isolation of so many people daily, sustained for one or two years, are not feasible in almost all countries and localities.

Contain the virus at the source

Now let's evaluate the proposal, in the previous entry from my blog , we analyze now how it behaves. To that objective, we created another simple model to evaluate how the possibility changes, of infecting another person or being infected, due to the constant use of plastic face masks and simple face masks, in a portion of the population.

There are reasonable assumptions here, to which some people may disagree. The invitation again is to go here and adjust it as you see fit: 

These results show that it is reasonable to stop the transmission of the virus in an economically and socially feasible way, with the use of plastic face masks + regularface masks. Likewise, this will work without confinement of the entire population, even though we double the number of meetings per person, per day. This is key to reviving the economy.

The broader use of mass transit systems in larger cities can also be allowed.

The simulations carried out by ECSIM based on the SIR model verified the operation of this effect. As you can see in the following graph, every time more people use these two elements simultaneously, the virus will not be present, the health system will not be overwhelmed to its maximum capacity, the economy will function almost normally. By this time, it is possible that we already have new treatments and vaccines available and the remaining economies have been normalized in one way or another. We will gain several months of advantage.

 Here I want to remind you of what was exposed in the first entry of this series:

This proposal is not a replacement for all other measures, which must be maintained: confinement of vulnerable people, routine hand washing, carry out as many PCR tests as possible on the population, controls with PCR tests for everything national or international traveler, biological checkpoints with tests at all borders and on access roads to those border areas and internal cities, body temperature and oxygen saturation (SO2) measurements, permanent disinfection in areas / structures / systems of transport, mobile applications for contact tracking(Bluetooth) and geo-referencing. etc.

Where the confinement-based solution fails

The physical isolation of the entire population not only generates a devastating impact on the economy, something that is felt almost immediately, it also generates another very important problem: it delays too long the time in which we obtain herd immunity.

That is another aspect that we must analyze in each possible solution, the total number of people infected over the total population. If there is no definitive solution, a vaccine, or a very effective treatment / medication in the coming months, the only alternative is to get closer, slowly but steadily, towards herd immunity. Permanent or alternate confinements do not allow it.

Although we have done very well in Colombia avoiding the hospital and human crisis, with respect to countries such as Spain, EUA or Italy, today they have many more total immunized citizens per million inhabitants than we do.

Populations without contagion

It is very important to remember that to date we have 926 communities in our country without a contagion, or about a third of the country's population, 16 million inhabitants. They are some of the most vulnerable places in the country in terms of their hospital infrastructure.

Although some are already doing so in a rudimentary way, the implementation of strict biological checkpoints at the entrance to these communities is urgent. Each person admitted must have a complete symptom’s check and, if possible, a diagnostic test. Then that person must wear mouth and nose masks and external plastic masks continuously, and do a complete disinfection routine before admission.

Any person native to the region who leaves the town and must return later, should also make compulsory use of plastic face masks and regular masks, all the time they are on the outside. Also have a complete washing & disinfection cycle of these elements, as well such as their clothing / vehicle before re-entry to the population.  

Conclusions

The only feasible option to complement the current measures, one that can be prepared in just a few days, is to make the use of plastic face masks and regular face (mouth and nose) masks, mandatory for at least 62 percent of their population in all cities. This could allow the majority of economic sectors to be released so that they can be back as active citizens.

The virus must be isolated, not the people.

Anything we manage to increase in daily diagnostic tests for Covid-19 will contribute to that goal, but it is not the key element.

There must be a different strategy for cities and towns that do not yet have the first infected inhabitant, by means of biological checkpoints at their entry and exit points and a standardized protocol by the national government that requires the use of a plastic face masks and regular face masks for anyone who leaves a community and return back to it.

If we have been recommended to cover our elbows every time we sneeze, it is logical then that the strategy should be rather to have the mouth and nose covered as long as possible al the day, with an element of any material.

If we have been told again and again to constantly wash our hands so as not to get contaminated when we touch our faces, it is logical then that the strategy must be focused on not making the face available to the contact of the hand, through the constant use of a plastic face mask.

To finish, I think this drawing is a good summary of this whole proposal. the values are indicative, since each particular case would have to be calculated accurately, but they are undoubtedly very representative of the ranges of probability of contagion, in each type of contact.

[1] Value officially released for Colombia by the Minister of Health in the previous week.

[2] In Paul Romer's original work, he indicates that 7 percent of diagnostic tests are required daily for 500 days, but this is the result of his analysis starting from a value of R0 = 2.4, for an epidemic situation of different Covid (possibly closest to a place without confinement).