Worldwide, this is the fifth confirmed episode of reinfection, according to that publication.

Verified by genetic sequencing, a Nevada patient tested positive for two SARS-CoV-2 infections within 48 days, confirming, according to the aforementioned study, that a second infection can occur in a short time frame and which may be more serious than the first.

The revealed findings also suggest that exposure to COVID-19 may not translate into a full guarantee of immunity, although, in relation to this point, the study warns that further investigation of reinfection cases is still necessary.

In that coronavirus reinfection episode - the first identified in that country - experts found evidence of an individual, with no known immune disorders or underlying medical problems, infected with SARS-Co-2 on two separate occasions.

The 25-year-old Washoe County, Nevada, patient was infected with two variants of COVID-19 in a 48-day period and tested negative between the two incidents.

The second infection was more serious than the first and the patient had to be hospitalized and required oxygen treatment.

The study authors warn that regardless of whether or not a person has been previously diagnosed with COVID-19, identical precautions should be taken to avoid contagion.

According to The Lancet, after testing positive for coronavirus last April, the aforementioned patient tested negative on two different occasions, but in June, after experiencing severe symptoms associated with the virus such as fever, headache, dizziness, cough, nausea and diarrhea, he was hospitalized and tested positive a second time.

Since then, he has already been discharged and has recovered from that second infection.

There are still many unknown factors about SARS-CoV-2 infections and the response of the immune system, but our findings indicate that a previous SARS-CoV-2 infection may not necessarily protect against future infection, says lead author of the study, Mark Pandori, of the Laboratory of Public Health of the State of Nevada - housed in the University of Nevada (USA) - and of the School of Medicine of Reno.

The expert considers that it is important to take into account that this is a singular finding and does not provide a generalization of this phenomenon.

While more research is needed, the possibility of reinfections could have significant implications for our understanding of COVID-19 immunity, especially in the absence of an effective vaccine, he notes.

Pandori adds that individuals who have tested positive for SARS-CoV-2 should continue to take serious precautions when it comes to the virus, such as maintaining social distance, wearing masks and washing their hands.

The study shows that the genomes of the virus samples from that patient were sequenced in April and June, showing significant genetic differences between the two cases, which implies that the patient was infected twice with SARS-CoV-2.

At least four other cases of reinfection of the virus have been detected globally in Belgium, the Netherlands, Hong-Kong and Ecuador, although only in the case detected in the latter country was the second episode of reinfection worse than the first.

The authors present several hypotheses to explain the greater severity of the second reinfection episode, among them that the patient had been exposed the second time to a large viral dose that would have caused a more acute reaction or that he had encountered a more virulent version of the virus.

But the tiny possibility of a continuous infection that implied some way that the virus had somehow been "reactivated" is now also being considered.

Pandori admits that, overall, there is a lack of broad genomic sequencing of COVID-19 positives both in the United States and globally, as well as a lack of tests, which limits the ability of researchers and health authorities to diagnose, monitor and obtain genetic history of the virus.