WHO Says Monkeypox Risk ‘Moderate’ – Transmision by Droplets, Mouth Lesions, Contaminated Bedding and Across Placenta
Rosamund Lewis and Sylvie Briand at WHO sponsored webinar Monday on Monkeypox

Monkeypox can be spread by an infected person through salive and droplets, including mouth lesions, as well as via bedding.  A mother can also pass the virus to her baby across the placenta.

In addition, untreated HIV might increase the risk of more serious infection.

So warned Dr Rosamund Lewis, the WHO’s monkeypox expert, at a WHO briefing on Monday where she described the current monkeypox outbreak in people with no contact with areas where the disease is endemic continues as “atypical”.

“What we don’t know is whether there is aerosol transmission – aerosolized transmission from talking and breathing,” said Lewis, speaking at a WHO webinar on Monday.

“We also don’t yet know whether there is asymptomatic transmission of monkeypox,” added Lewis.  “The indications in the past have been that this is not a major feature, but this remains to be determined.”

Public health risks “moderate” says WHO as virus spread farther than in the past

In a statement on Sunday, WHO said it had recorded 257 cases of the disease since 26 May, outside of the 12 central and west African countries where the disease is endemic. All of the cases have been diagnosed with the West African clade of monkeypox, which is less deadly than the central African one.

In contrast, only nine cases have been identified outside these regions over the past five years and all those cases involved people who were linked to these regions by travel.

“Currently, the overall public health risk at global level is assessed as moderate considering this is the first time that monkeypox cases and clusters are reported concurrently in widely disparate WHO geographical areas, and without known epidemiological links to non-endemic countries in West or Central Africa,” the WHO statement said.

“Cases have been mainly reported amongst MSM. Additionally, the sudden appearance and wide geographic scope of many sporadic cases indicates that widespread human-to-human transmission is already underway, and the virus may have been circulating unrecognized for several weeks or longer.”

Transmission rates generally have not been that high in the past

Transmission rates have not generally been that high in the past, and “it is a large DNA virus, one of the largest viruses known, and it would change or mutate much more slowly than RNA viruses”, Lewis said.

“There is not much information right now. We are just seeing the first genomes being put up and don’t have a lot of information on what the genomes of the viruses being detected in this current multi-country outbreak are telling us,” added Lewis. 

However, she said that it was not yet known whether people immunised against smallpox 40 or 50 years ago would still have immunity.

“We are concerned that the global population is not immune to orthopox viruses since the end of the small pox eradication.. The virus may attempt to exploit a niche and spread more easily between people.”

Congo Basin clade more severe

The Congo Basin clade appears to cause severe disease more frequently with case fatality ratio (CFR) previously reported of up to around 10%, said the WHO statement, adding that nonetheless, the Democratic Republic of the Congo, where the disease is most prevalent,  is reporting a CFR among suspected cases of around 3%.

“The West African clade has in the past been associated with an overall lower CFR of around 1% in a generally younger population in the African setting. Since 2017, the few deaths of persons with monkeypox in West Africa have been associated with young age or an untreated HIV infection.”

WHO’s Dr Sylvie Briand said that unlike COVID-19, monkeypox was a known disease with symptoms, including ever, muscle aches and swelling of the lymph nodes – with skin eruptions within three days of the onset of fever.


Image Credits: US Centers for Disease Control.

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