epidemiological features, disease severity, and the impact of smallpox vaccination

The first detection and transmission of the monkeypox virus (MPXV) outside its endemic areas in May 2022 was followed by a huge multi-country outbreak worldwide. As of the 23rd of August 2022, a total of 42,807 cases along with 12 deaths were reported across 97 member states that belong to six World Health Organization (WHO) Regions. It was declared a public health emergency of international concern (PHEIC) by the WHO director on the 23rd of July, 2022.

Study: A large multi-country outbreak of monkeypox across 41 countries in the WHO European Region, 7 March to 23 August 2022. Image Credit: Dotted Yeti/Shutterstock

A new study published in Eurosurveillance aimed to analyze the epidemiological features of MPX, disease severity, as well as the impact of smallpox vaccination on all infected cases that were reported in the WHO European Region.

About the study

The study was carried out using data submitted to the European Surveillance System (TESSy). Nowcasting of the TESSy data was carried out up to 17 days before the last reported symptom to understand the current epidemiological situation.

Study findings

The first non-travel-associated family cluster of MPX cases was reported to the WHO by the United Kingdom (UK) on the 13th of May 2022, following which it was reported in other neighboring countries. The MPXV cases were found to be caused by Clade II (formerly West African clade) and most commonly affected men who have sex with men (MSM). Europe remained the epicenter of this outbreak until the end of July.

Out of the total 21,098 cases detected in the WHO European Region, 20,690 cases provided case-based data, most of which were laboratory confirmed. Nowcasting results suggested an overall plateauing of cases with a few inter-country differences. Additionally, most cases were males with a median age of 37 years. Among them, 96.9% self-identified themselves as MSM, while 37.2% were found to be HIV positive. Very few cases were reported among children and women.

The most common symptoms were rashes along with at least one systemic symptom, such as fatigue, fever, muscle pain, headache, or chills. 48.1% of cases reported the occurrence of rashes in the anogenital region. Moreover, 6% of cases were reported to require hospitalization, with three requiring admission to an intensive care unit (ICU). Out of these three cases, two were found to die of encephalitis.

Furthermore, the case hospitalization ratio was reported to be 10 per 1,000 cases, with younger cases having a higher risk of hospitalization. Regarding transmission routes, sexual contact was the most possible route followed by person-to-person routes or fomites. Exposure at bars and household exposures were also reported to play a role in transmission. Additionally, 64 of the cases were observed in health workers, of whom 62 were male, and 55 were MSM.

Concerning smallpox vaccination, most cases reported being unvaccinated before and for this outbreak, 423 reported getting vaccinated before the outbreak, and 42 reported post-exposure preventative vaccination (PEPV). In contrast, one reported primary preventive (pre-exposure) vaccination (PPV). However, the impact of smallpox vaccination was observed not to be quite significant.

Therefore, the current study demonstrated the pattern of virus transmission, the vulnerable population, as well as impact of vaccination. However, a strong interaction between public health authorities, communities, and international health organizations is required to overcome the current outbreak of MPXV infections.

Limitations

The study has certain limitations. First, the data submitted to TESSy can vary in completeness and depend on the availability of national data. Second, clinical data submitted to TESSy does not indicate the full course of the disease. Finally, the nowcasting estimates might be uncertain.

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