epidemiological characteristics, disease severity and 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 outbreak in several countries around the world. As of 23 August 2022, a total of 42,807 cases and 12 deaths have been reported from 97 Member States belonging to six World Health Organization (WHO) regions. It was declared a public health emergency of international concern (USPPI) by the director of the WHO on July 23, 2022.

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

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

About the study

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

Study results

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

Of a total of 21,098 cases detected in the WHO European Region, 20,690 cases provided case-based data, most of which were laboratory confirmed. The nowcasting results suggest an overall plateau in cases with some differences between countries. Additionally, most cases were male with a median age of 37 years. Of these, 96.9% identified as MSM, while 37.2% tested HIV-positive. Very few cases have been reported in children and women.

The most common symptoms were skin rashes accompanied by 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. Additionally, 6% of cases required hospitalization, with three requiring admission to an intensive care unit (ICU). Of these three cases, two died of encephalitis.

In addition, the case hospitalization ratio was 10 per 1,000 cases, with younger cases at higher risk of hospitalization. Regarding transmission routes, sexual contact was the most possible route followed by person-to-person routes or fomites. Bar exposure and household exposure have also been reported to play a role in transmission. Additionally, 64 of the cases were seen in health care workers, of which 62 were men and 55 were MSM.

Regarding vaccination against smallpox, most cases reported not having been vaccinated before and for this epidemic, 423 declared having been vaccinated before the epidemic and 42 declared having received post-exposure preventive vaccination (PEPV) . In contrast, one reported preventive (pre-exposure) primary vaccination (PPV). However, it was observed that the impact of smallpox vaccination was not entirely significant.

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

Limits

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

Leave a Reply