Researchers at the Institute of Tropical Medicine (ITM) in Antwerp have provided evidence showing that people infected with the mpox virus (formerly monkeypox virus) may be able to transmit the disease even before they have symptoms. Samples from high-risk contacts indicate this. The ITM says this could be an important explanation for the spread of the virus.
In Belgium and the rest of Europe, the mpox epidemic is waning. Since the first case in May, we have learned a lot about the virus and how it spreads. A few months ago, it emerged that the mpox virus, formerly called monkeypox virus, can be contagious even without symptoms. Now scientists are showing that even in infected people, the potentially transmissible virus can be present even before the symptoms appear.
Close follow-up of high-risk contacts
The ITM study team investigated the risk of infection following a high-risk contact. Twenty-five high-risk contacts such as sexual partners and roommates of infected persons took daily samples that were examined at ITM’s laboratory. Participants also kept a diary and were closely monitored by healthcare workers, with necessary advice and appropriate care.
Key explanation for spread
‘The results of the PCR tests showed that participants were potentially infectious sometimes as early as four days before they tested positive,’ says Koen Vercauteren, clinical virologist at ITM. The results also teach us other things about the virus. First, the risk of infection through sexual contact is much higher than we have previously assumed. The risk of infection through non-sexual contact, on the other hand, is very low. Secondly, although skin lesions are a characteristic symptom, they are less common than we assumed. In the study, less than half of the infected participants showed typical symptoms, and only a third showed skin lesions.