A genetic study of the first 28 virus genomes rules out the existence of a so-called ‘patient-zero’ in Spain.
THERE are 30,000 numbers in the genetic code of the new coronavirus. Once it infects a cell, for example in the throat, the virus is capable of making up to 100,000 copies of itself in just 24 hours. In each of these copies, small errors can arise, which are then passed on to the next copies of the virus. The study of these viral types will inherently tell us about the history of the pandemic.
This is what a team of scientists at the Carlos II Health Institute in Madrid have been doing. They have already analysed the first 28 virus genomes that were recorded in Spain.
However, tracing these variations back does not lead them to a single ‘patient zero’ but rather it confirms a ‘multitude of entries’ from people infected from other countries during the month of February.
On February 23, the Emergency Coordinator of the Ministry of Health, Fernando Simón, stated: “In Spain there is no virus, nor is the disease being transmitted, nor do we currently have any cases.” But it seems that by then the virus was already moving across the nation with ease.
Díez’s team has studied the nearly 1,600 complete virus genomes recorded by the international scientific community until the end of March. The analysis shows that the 28 Spanish genomes belong to the three larger virus families identified in the rest of the world and named S, G and V, with little diversity among them.
“All viruses are very similar, in principle, with few differences in mutations, which is good news,” says Diez, who now works at the Hospital Clinic in Barcelona. The experimental vaccines being investigated today are designed for the current genetic sequence of the virus. A high mutation rate could ruin the effectiveness of the first vaccines, which will arrive within a year at the earliest.
The new analysis suggests that the common ancestor of the 1,600 coronaviruses studied was found in the Chinese city of Wuhan around November 24, 2019.
Thirteen of the Spanish genomes belong to the S family, and 11 of them are linked to a previous case detected on February 1 in Shanghai.
The first three S genomes identified in Spain are from samples taken on February 26 and 27 in Valencia. A week earlier, 2,500 Valencia fans had traveled to Milan to watch the Atalanta-Valencia soccer match, described as “a biological bomb” by the mayor of Bergamo, Giorgio Gori.
“In Spain there has been no patient zero. There is no patient zero when an epidemic is already so widespread,” stresses the virologist José Alcamí.
Based on the information we have today, we believe that there were at least 15 different entries in Spain. Something similar to this has happened in other countries, such as the USA and Iceland, where they have also been multiple entries of the virus,” says González, “patient zero does not exist.”