(Reuters) – The first human challenge trial, in which people were exposed to coronavirus in a deliberate setting, has shown that symptoms have no impact on the likelihood of an infected person passing the disease to others.

These findings highlight the difficulties in controlling community infections, as the World Health Organization (WHO), warns that there will be an increase in the number of cases.

Open Orphan, London with Imperial College conducted the study and found that symptoms or the fact that they were present at all was not related to their viral load.

Two methods were used to measure the viral load (or tendency to shed virus): focus-forming assays (FFA), and quantitative polymerase chains reaction (qPCR).

Researchers concluded that “there was no correlation between FFA or qPCR viral shedding and symptoms score” in a paper published in Nature Medicine.

In the Imperial trial, 36 young healthy adults were exposed to the SARS-CoV-2 virus. They were monitored in quarantine.

Two volunteers had antibodies to the virus, so they were not included in the analysis. A little more than half contracted the virus.

According to earlier statements by the researchers, there was no evidence of serious adverse effects and the human-challenge study model proved safe for healthy young adults.