Scientists have found that the spread of monkeypox can occur up to four days before any symptoms appear.
Before symptoms appear, the spread of the disease may be “much worse” than previously thought, according to researchers from the UK Health Security Agency (UKHSA).
In the first evidence of its kind, the study estimated that more than half (53%) of transmission occurred in the presymptomatic stage, meaning that many infections cannot be prevented by requiring people to isolate when symptoms are detected.
It also suggests that even if contacts are traced, they may have spread the virus to others.
The study concluded that people would need to quarantine for 16 to 23 days to detect 95% of potentially infected people.
The researchers looked at the time from the first symptom onset in the first patient to the onset of symptoms in the second patient, as well as the incubation period – the time from exposure to the virus to the onset of symptoms.
The findings showed that four days was the longest time that transmission was detected before symptoms appeared.
monkeypox Symptoms vary, but include rash, fever, chills, swollen lymph nodes, fatigue, and headache.
The latest UKHSA figures show that as of October 24, there have been 3,548 confirmed cases of monkeypox and 150 “highly probable” cases of monkeypox in the UK.
Monkeypox: How did you get it, what are the symptoms, and how easily does it spread?
Infections peaked at more than 60 a day in mid-July, but have since declined, averaging less than 15 cases a day in early September.
The study included 2,746 people who tested positive for monkeypox in the UK between May 6 and August 1.
Their average age was 37.8 years, and 95 percent reported being MSM.
‘It remains critical that people remain vigilant about risks’
Dr Nachi Arunachalam, UKHSA’s Director of Monkeypox Incidents, said: “This modelling suggests that monkeypox may be transmitted when people are pre-symptomatic or before they realise they have symptoms, but more work needs to be done to understand pre-symptoms. Symptomatic infection, and what this might mean for future policy and management of monkeypox outbreaks.
“While we are seeing continued reductions in reported cases in the UK, it remains vital that people remain vigilant about the risks posed by monkeypox and take action to protect themselves and others.
“Vaccinations play a vital role in this, so I would encourage those at highest risk to come forward and get your first dose of the vaccine.”
45,000 people vaccinated
In September, UKHSA announced a second dose of smallpox vaccine to people at high risk of monkeypox.
More than 45,000 people received a dose of the vaccine, including more than 40,000 men who had sex with men. These groups are at the highest risk of exposure to monkeypox.
The study was published in the British Medical Journal (BMJ).