New Research Found “Substantial” Evidence That Monkeypox Transmission Occurs Prior To Symptom Onset
Ever since experiencing an international monkeypox outbreak in May of this year, there have been nearly seventy-nine thousand cases worldwide, according to the CDC.
The CDC’s most recent guideline on monkeypox isolation and prevention, which was updated on October 18, 2022, also states that the spread of infection occurs after symptom onset.
“In the current global outbreak, monkeypox has only been known to spread by people from the time symptoms start until the rash has fully healed and a fresh layer of skin has formed,” the guideline says.
But, according to a new study published in the British Medical Journal earlier this month, there was “substantial” evidence that monkeypox can be transmitted pre-symptomatically– or before symptoms are detected or appear.
Previous research on the monkeypox virus did not explicitly rule out this possibility. However, no research ever supported pre-symptomatic transmission– until now.
In fact, monkeypox transmission was detected up to four days prior to symptom onset.
The researchers also estimate that fifty-three percent of virus transmission took place during this pre-symptomatic phase.
This means that preventive efforts are ineffective if individuals are being asked to isolate after they become symptomatic.
And if these findings are corroborated by other studies, the research team believes that pre-symptomatic transmission could have drastic implications for global infection control.
pucko_ns – stock.adobe.com – illustrative purposes only, not the actual person
Monkeypox cases have been declining since the initial outbreak.
But, understanding the root of transmission– such as how the virus spreads throughout communities and how soon symptoms appear– is crucial for informing government policy and intervention efforts.
To understand these findings further, researchers from the UK Health Security Agency also analyzed monkeypox’s transmission dynamics by studying the UK outbreak.
They used contact tracing and routine surveillance data for over two thousand and seven hundred individuals who tested positive for the virus between May 5 and August 1.
The average age of the individuals was thirty-eight, and ninety-five percent reported being bi, gay, or men who are intimate with other men.
The team found that the virus’ average incubation period– which is the time between exposure and onset of symptoms– was 7.6 days using one statistical model. A second model found the incubation period to be 7.8 days.
Both models also had discrepancies in terms of mean serial interval– or the average time between symptom onset among a primary patient to symptom onset in a secondary contact.
But, both models had a median serial interval between 0.3 and 1.7 days less than the median incubation period.
So, in other words, the researchers found that significant transmission occurs before symptoms appear or are detected.
This finding was also supported by an analysis of the individuals’ specific patient data since ten out of thirteen case-contact patient pairs reported experiencing pre-symptomatic transmission.
In turn, the researchers concluded that an isolation period of sixteen to twenty-three days is required in order to detect up to ninety-five percent of people who are potentially infected.
It is important to note that the research is based on observational findings and that there were numerous limitations to this study– including how the team relied on contact tracing and self-reported data on symptom onset.
Still, the researchers believe that if their findings are representative of the international community, they could massively impact contact tracing and isolation policies.
More specifically, contact tracing would need to account for pre-symptomatic infectious periods.
To read the study’s complete findings published in the British Medical Journal (BMJ), visit the link here.
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