How is a case of coronavirus confirmed? The Nobel prize-winning invention that allows us to keep track of the virus

On Friday, January 31, the Ministry of Health confirmed the first case of new coronavirus in Spain in La Gomera. The patient, of German nationality, had previously been in contact with a patient diagnosed with coronavirus in Germany. At this time, this person and four others who had also been exposed to the same individual with the infection are admitted to observation and isolated at the Virgen de Guadalupe de la Gomera Hospital.

Currently, it is estimated that 20% of people affected by the coronavirus develop serious complications such as pneumonia and respiratory distress, especially in people at risk (old age, chronic diseases, babies ...). The vast majority of those affected by coronavirus show mild symptoms (similar to a cold or flu), which means that many of them do not go to the health centers for a diagnosis. This, along with other reasons, has led to various public health experts To estimate that the number of patients who have been infected by coronavirus in China is, in fact, much higher than confirmed cases, which would mean that the actual lethality of the virus is much lower than 2-3%.

Although it is practically impossible to confirm all cases before an epidemic of a disease that has spread throughout a country and that almost always presents with mild symptoms, being confused with other common ones, confirmation of the diagnosis of coronavirus is essential to know details such as lethality of the virus, its extension among the population and what signs and symptoms it causes in the affected patients.

In Spain and according to Health, those cases that show typical symptoms and have been in close contact with confirmed cases (for example, being less than two meters) or who have recently visited the province of Hubei are declared as suspected cases of coronavirus (China). In addition, since the incubation period of the virus can be quite long (up to 14 days), those without symptoms are also put under observation, but with close contact with confirmed cases or presence in the critical place of the epidemic ( as is the case with the repatriated Spaniards of Wuhan). Only if symptoms develop, samples would be sent to the National Microbiology Center (CNM), which is responsible for centralizing the evidence of patients suspected of carrying the virus and officially confirming the results.

Before suspicious patients with symptoms, there is a detailed protocol, published by the World Health Organization (WHO) on January 17, on the different steps to confirm whether they are really cases of new coronavirus. In this regard, the detection by laboratory tests of a 2019-nCoV virus infection is defined as a confirmed case, regardless of symptoms and clinical signs. Samples useful for laboratory analysis range from nasal or pharyngeal secretions, passing through sputum (expectorations of the bronchial tubes, throat and nose that spits through the mouth) to biopsies of lung tissue in the case of deceased.

Although there are different laboratory techniques to check the presence of the coronavirus in a patient's body, the real-time polymerase chain reaction (RT-PCR) is currently recommended by health authorities such as WHO for its reliability and speed (it is done in a matter of hours). Its original variant, PCR was a revolution for molecular biology decades ago because it allows the rapid and simple expansion of DNA or RNA which makes it possible to carry out numerous genetic tests. Its inventor, Kary Mullis, received the Nobel Prize in Chemistry in 1993 for this advance.

The operation of RT-PCR is, in essence, simple. Thanks to the genome sequencing of the new coronavirus from different places, we know its nucleotide sequence (A, U, C and G) in its genes, that is, the order and combination of the "letters" in its RNA (there are viruses with DNA and RNA virus). In addition, we also know what letter sequences in the new coronavirus are characteristic of this for specific genes and different from the other coronaviruses.

For the realization of a RT-PCR, a series of molecules (which come in diagnostic kits) are added together with samples of the suspect in an apparatus called thermocycler so that only the expansion of very specific sequences of a virus occurs and not of other. If these sequences exist, they are amplified and are marked by fluorescence in the thermal cycler being detected as a fluorescence signal that increases over time. If the new coronavirus were not present, this genetic material would not expand and no fluorescence signal would be detected. To guarantee a positive result it is not recommended to do a single test but two, with different genes of the 2019-nCoV virus. In addition, there are reference laboratories in the European Union that accept receiving samples to confirm any positive test that would have been given in this territory.

In addition to the diagnosis by RT-PCR the health authorities also recommend the sequencing of the virus to know details such as knowing where it comes from or the new mutations that may be present. Knowing how the new coronavirus is genetically in different parts of the world is very useful for microbiologists to know how this microorganism moves, what is its ability to mutate and what weaknesses it has for the development of a vaccine. And is that knowing the genetic sequence of the coronavirus not only allows us to keep track of it throughout the world, but also fight it in the future.