In August 2024 the Public Health Agency of Sweden announced that a person who sought care at Region Stockholm has been diagnosed with mpox caused by the clade 1 variant. This is the first case caused by clade 1 to be identified outside the African continent. The notification from the Public Health Agency came shortly after WHO declared the mpox outbreak in the Democratic Republic of the Congo and neighbouring countries a public health emergency of international concern (PHEIC).
The infection in Sweden
Professor Magnus Gisslén, state epidemiologist at the Public Health Agency of Sweden stated that the person developed the infection during a visit to a part of Africa where there is a major outbreak of mpox clade 1. This person has received “care and rules of conduct”.
“This case does not require any additional infection control measures in itself, but we take the outbreak of clade 1 mpox very seriously. We are closely monitoring the outbreak and we are continuously assessing whether new measures are needed.”
Although previous cases of mpox in Sweden have been clade 2, the Public Health Agency highlights its “preparedness to diagnose, isolate, and treat people with mpox safely”. Sweden also has access to vaccines and antivirals.
A “concerning” development
Dr Jonas Albarnaz, Research Fellow at The Pirbright Institute, describes the case of clade 1 mpox in Sweden as “concerning for two main reasons”.
“First, this is the first clade 1 mpox virus outside Africa. This indicates that the extent of the international spread of clade 1 outbreak in DRC might be larger than we knew yesterday. And second, clade 1 mpox virus is associated with a more severe disease and higher mortality rates than the clade 2 virus responsible for the international mpox outbreak in 2022.”
Although it is “hard to predict” further cases of this clade outside Africa, Dr Albarnaz states that this case is a “warning call” to be “vigilant and implement robust surveillance and contact-tracing strategies”.
Associate Professor of Immunology at the University of Cambridge, Dr Brian Ferguson agrees that this case is a “concerning development”. However, it is “not surprising, given the severity and spread of the outbreak in Africa”. Furthermore, there will “likely be more here and in other parts of the world” as there are “no mechanisms” to prevent imported cases. Dr Ferguson comments on the timing of this case, under 24 hours after the PHEIC declaration and 15 months after the end of the previous mpox PHEIC.
“The lack of activity in the intervening period has resulted in what could now become a new global outbreak. There should have been a greater effort to produce and distribute vaccines to the affected areas, but this has not happened. It is possible to address these problems, but this requires rapid international co-operation.”
Professor Francois Balloux, Professor of Computational Systems Biology and Director, UCL Genetics Institute, emphasised that there is “no evidence for transmission in Europe at this stage”. However, it is “to be expected” that other imported cases” will be identified outside Africa soon.
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