#18,301
Yesterday the UK's Health Security Agency (UKHSA) released its first major technical briefing on Mpox since September of 2022, which previously dealt almost exclusively with the international spread of the milder Clade IIb virus.
Since then, a more severe, and more transmissible, Clade Ib has emerged in the DRC and has begun to spillover into neighboring countries, leading to the declaration of a new PHEIC (Public Health Emergency of International Concern) last month by the WHO.
Due to limited surveillance and testing in the DRC (only about 20% of suspected cases are ever confirmed), we only have a limited understanding of the severity or transmissibility of this new threat. The WHO reported last weekend:
- Mpox case fatality ratio in the Democratic Republic of the Congo in 2024 is 0.5% among confirmed cases (25 deaths out of 5160 cases) and 3.3% among suspected cases (717 deaths among 21 835 cases).
While the risks of sustained community spread of Mpox Clade Ib outside of Central Africa is currently believed to be low (see ECDC Assessment), we are dealing with limited data, and the reality that this virus continues to evolve.
Since it is prudent for a public health agency to consider all `reasonable' scenarios, the UK's updated Mpox Technical Briefing # 9 presents 3 possible scenarios for the spread of Mpox in the UK ranging from the least to most impactful.
While most countries outside of Africa appear to be operating under the assumption that Mpox will remain a minor public health threat (similar to scenario A), this report relies heavily on adjectives like `limited' and `insufficient' to describe our current understanding of how this virus spreads.A) incursions and small clusters of cases,
B) a controllable epidemic, and
C) community transmission
As this is a 21-page report, I've only posted a few small excerpts. Follow the link to read it in its entirety.
Mpox: scenarios and technical elements of preparedness and response for clade I
Technical Briefing 9
12 September 2024
Introduction
(Excerpt)
There is an ongoing outbreak of mpox caused by clade I MPXV in Central Africa, including increased clade Ia cases in Democratic Republic of the Congo (DRC) and a spreading outbreak of clade Ib. There is evidence of sustained human to human transmission for clade Ib, which is a novel clade with limited characterisation. Clade I MPXV is reported to cause more severe disease than clade II and is currently considered a High Consequence Infectious Disease (HCID) in the UK.
Whilst there are low numbers of clade II cases in the UK (Figure 1), no clade I has been detected in the UK to date. This briefing covers technical elements of risk assessment, preparedness and response activities for clade I mpox with a domestic UK focus. The Foreign, Commonwealth and Development Office (FCDO) leads on the UK’s activities in support of affected countries.
Part I Outbreak in the UK
A key uncertainty in the epidemiology of clade Ib is transmissibility and mode of transmission. The following 3 scenarios have been developed to illustrate how MPXV with different levels of transmissibility between humans might spread, and the challenges that they might pose to the UK health system. These are illustrative scenarios and are not predictions or projections, neither are they exhaustive.
All scenarios presented here assume there is an ongoing outbreak in Africa which seeds other countries regularly through international air travel. The UK is highly connected by air travel, and it is assumed that the UK receives multiple separate importations of infection. The scenarios are focused on clade Ib, which shows genomic evidence of sustained human-to-human transmission (Vakaniaki and colleagues) and is associated with the geographically spreading outbreak.
Each scenario posits a different level of transmissibility, that is a different probability that any given contact of a case will become infected. Transmissibility relates to multiple different viral properties such as amount of shedding, duration of shedding and mode of transmission, but these are not considered separately for the purposes of the illustrative scenarios.
(SNIP)
(SNIP)
Transmission
• All MPXVs can spread by direct (touch) contact with an infected person or their body fluids or contact with surfaces or items contaminated with the virus.
• Whilst evidence is gathered on modes of transmission in this new outbreak, it is recommended that respiratory transmission risks are mitigated, noting that virus and/or lesions can be present in the respiratory tract in some cases.
• Transmission by sexual contact appears to be contributing to the spread of clade Ib MPXV in some of the currently affected countries. The transmission pattern of clade Ia is less well described but may be driven by person to person (non-sexual) close contact.
• There is little evidence available on MPXV in genital secretions as opposed to skin lesions on or near genitalia. Therefore, on a precautionary basis, genital secretions (for example, semen) should be considered as potentially infectious for 12 weeks after symptoms have resolved.
• MPXV should be assumed present in the respiratory tract of infected patients and in healthcare settings the standard aerosol generating procedure infection control practices should be applied. Deroofing lesions and throat swabs are not considered to be aerosol-generating procedures (AGPs) although they may generate droplets. A list of AGPs is available in the local country-specific national infection prevention control manuals.
Incubation and infectious periods
• The incubation period usually lasts between 6 and 13 days but with a maximum described range of 5 to 21 days. There may be a prodrome; if so, the rash appears between 1 and 5 days after the initial onset of symptoms.
• The assumed infectious period is from the onset of symptoms until lesions have scabbed over and the scabs have fallen off and a fresh layer of skin has formed underneath. Shedding of clade II MPXV DNA in upper respiratory tract swabs has been detected for at least 3 weeks but is of unclear significance for transmission.
• There are insufficient data on which to assess transmission of clade I before a person develops symptoms, but this will be kept under review.
Clinically at-risk groups
• There is currently insufficient information available to fully characterise the severity of clade I. The reported case fatality rate is lower than that of clade Ia, although not as low as clade IIb; however, the different populations affected by the outbreaks may mean that the current CFRs are setting specific.
• Based on available data from both clade I and clade II, children under the age of 15 are considered to be a group at risk of severe disease, with children under 5 at highest risk.
• Based on available data from clade II, immunocompromised people and pregnant people are considered to be a group at risk of severe disease from clade I.
• There is no available data to assess severity in the elderly. On a precautionary basis and despite prior smallpox vaccine, elderly individuals will be managed as an additional high-risk group.
Virus survival
• Poxviruses show high environmental stability and can survive in the environment and on different types of surfaces from 1 to 56 days depending upon the temperature and room humidity. Evidence on the survival of MPXV is limited; however, viable MPXV has been detected on household surfaces at least 15 days after contamination of the surface.
• There is currently limited data on transmission of poxviruses via contaminated objects or materials, aside from linens such as clothing or bedding. Therefore, thorough environmental decontamination is required to reduce the risk of transmission from contaminated objects or materials
