GENEVA: The global response to mpox is clouded by uncertainty as experts grapple with the disease’s risks, mortality rates, and the implications of various viral clades. The World Health Organization (WHO) declared a global public health emergency over mpox in July, but fundamental questions about the disease’s dangers and the differences between its variants remain unresolved.
Mpox, which was first identified in humans in 1970 in the Democratic Republic of Congo (DRC), was traditionally confined to a few African nations. Historically, its mortality rate ranged between 1% and 10%. However, the disease’s profile changed significantly in 2022 when it began spreading beyond Africa, particularly to Western countries.
In these new regions, the mortality rate for mpox has been notably low, around 0.2%. This sharp contrast with the higher rates observed in Africa has led to speculation about the reasons behind these differences.
According to Antoine Gessain, a virologist specializing in mpox, the quality of medical care plays a crucial role. “The danger mpox presents strongly depends on the quality of basic care,” Gessain explained. In countries with advanced healthcare systems, like those in the US and Europe, the mortality rate is significantly reduced compared to areas with less access to medical resources.
The current outbreak in the DRC has resulted in a mortality rate of approximately 3.6%, a figure that would likely be lower if the disease were not predominantly affecting regions with limited healthcare. The majority of deaths in the DRC have been among children, many of whom suffer from malnutrition. In contrast, the 2022-23 epidemic in the DRC, which primarily affected adults with pre-existing conditions like HIV, had a lower fatality rate of around 0.2% in a larger cohort of 100,000 cases.
Complicating the picture further are the various clades or viral families of mpox. The 2022-23 epidemic was caused by Clade 2, which is mainly found in western Africa but is also present in South Africa. The current outbreak in the DRC involves Clade 1, typically seen in central Africa. Within Clade 1, a newly identified variant, 1b, is causing concern due to its recent emergence and potential differences from earlier strains.
Marion Koopmans, a Dutch virologist, cautioned against drawing hasty conclusions about the relative danger of different mpox clades. “There are rather big claims in the popular media for which evidence is limited, both about the severity and about the transmissibility of the new sublineage 1b,” Koopmans noted.
She confirmed that while Clade 1 has been associated with more severe disease compared to Clade 2, definitive comparisons are challenging. “How can you compare children suffering from malnutrition and HIV-positive adults?” Gessain added, emphasizing the complexities of comparing mortality rates across different contexts.
The detection of Clade 1 in Sweden in mid-July, the first instance of this clade being identified outside Africa, underscores the need for continued vigilance and research.
