All eyes are on May 9. That is the last day of the extended state of alarm period that the government will officially request today in Spain’s Congress of Deputies, and it is, according to Prime Minister Pedro Sánchez, the date from which the current coronavirus confinement measures in Spain can begin to be relaxed.

The survey was scheduled to begin last week, but “certain adjustments” have led to delays

A key tool that the Health Ministry had announced for deciding on how these first steps will take shape was a serological survey that would reveal the incidence of the SARS-CoV-2 virus in Spain. But the results of that testing will not be ready by that date: the process is due to start on Monday and will last for eight weeks.

The survey was scheduled to begin last week, but “certain adjustments,” according to Fernando Simón, the director of the Health Ministry’s Coordination Center for Health Alerts, have led to delays. The Health Ministry shared the plans for this survey with Spain’s regions on Monday. The objective is to determine the real number of people infected in the country, and potentially, how much of the population is immune to the disease. The document that was sent out, to which EL PAÍS has had access, shows that after a training and testing period, the surveys will begin on April 27 at the earliest.

The tests will be carried out in primary healthcare centers, unless a home visit is essential. A number of regional governments that were consulted by this newspaper have explained that they are preparing the resources necessary. Antonio Fernández Pro-Ledesma, the president of the Spanish Society for General and Family Doctors, said that they have no more information than what they are reading in the media. “We have the sufficient capacity and versatility, but we cannot carry on doing more with the same resources,” he said. “We will have to see the methodology and how [the tests] are going to be done.”

The survey will be carried out on 36,000 households that have been chosen by Spain’s National Statistics Institute. They are located across Spanish territory and cover all age sectors from the population pyramid in a proportional manner. Around 90,000 people in total will be tested, according to the document.

Each person will be subject to two types of tests three times, with a three-week gap between sampling

Each person will be subject to two types of tests three times, with a three-week gap between sampling. There will be a rapid inmunocromatographic test, which in 10 minutes detects antibodies after a simple pinprick method. And also, a more complete blood test will be carried out known as Elisa, which offers a full analysis of the quantity of the immune response that has been generated.

With these two tests, repeated on three occasions, the aim is to have the most complete view of the immunity that has been generated, as well as how it evolves over time and if there are new infections on the way.

If the more optimistic targets are met, in the next two weeks a first round of testing will have been completed, meaning that the initial results will arrive after decisions have been taken about the early deescalation steps.

Simón explained on Tuesday that the survey is “an important tool, but not the only one.” The other factors that will be taken into account are the real transmission rates of the disease, for which, the Health Ministry said, it is already carrying out 100,000 tests a day, and the capacity of the country’s health systems. “Faced with the risk of new waves of the epidemic, even if they are potentially minor, we can’t allow for the system to be put under the strain it has already suffered,” he said.

Experts consulted by EL PAÍS explain that the survey will provide fundamental information about the coronavirus, including how many asymptomatic infections there have been, where and how it has spread, and whether it is still latent without our knowledge.

Regional differences

“For concrete measures, such as letting out children, perhaps it isn’t the most useful thing, but for more general ones, it is,” explained a spokesperson from the Spanish Society for Preventive Medicine, Public Health and Hygiene (SEMPSPH). “It will also be crucial for new waves, to prepare systems according to the incidence that there has been in one place or another. It will not be the same in a region where there is a large number of people who have had the infection than in another with very few,” the spokesperson continued, pointing out that it is still not clear what level of immunization people who have overcome Covid-19 are left with.

José Martínez Olmos, an expert in public health and the general secretary of Health between 2005 and 2011, believes that the survey is one more tool that can be used to take decisions, but is “not essential.” “Although it will help later on, the important thing is that it be done well. It would be advisable to count on the best information possible about the incidence among the population, but in the meantime what needs to be done is to prepare the system and to have epidemiological monitoring on alert should cases appear, in order to locate them, isolate them, and if necessary, retreat.”

English version by Simon Hunter.