Mpox public health emergency declared; Rising parvovirus activity in the U.S.

Two significant mid-week updates:

Increase in parvovirus activity in the United States

Yesterday, the U.S. Centers for Disease Control and Prevention sent out an alert warning of an increase in human parvovirus B19 activity.

Parvovirus B19 is common — parents may know it as "fifth disease" or "slapped cheek syndrome" because it causes a red rash on the cheeks after flu-like symptoms. It mostly affects children, and it spreads primarily through respiratory droplets when an infected person coughs or sneezes.

“Slapped cheek” rash. Source: CDC

Children usually recover well at home, but infection can be dangerous for certain groups. In pregnant women, it can lead to complications, while people with severe immunocompromise or certain blood disorders (like sickle cell disease) may experience severe anemia.

Epidemiologists have identified a recent increase in activity. The proportion of people with recent parvovirus B19 infection, indicated by IgM antibodies, rose across all age groups from less than 3% in 2022–2024 to 10% in June 2024. The largest increase was in children aged 5–9, where rates jumped from 15% to 40%.

The same strategies for Covid-19 prevention apply to parvovirus B19 prevention: masking, attention to air quality including through improved ventilation, and basic handwashing etc.

Mpox declared public health emergency

I’ve been reporting in Outbreak Outlook on a months-long increase in mpox activity, first in the Democratic Republic of Congo and now in other countries in the region. Today, WHO Director-General Tedros Adhanom Ghebreyesus declared the situation Public Health Emergency of International Concern.

This follows a similar declaration made by Africa CDC, deeming the epidemic a Public Health Emergency of Continental Security. This is the first such declaration made by Africa CDC.

The situation in the DRC is complex, with multiple lineages or variants of mpox circulating. Current evidence suggests these lineages may have different patterns of spread. For instance, clade II, which caused the 2022 global outbreak, primarily spread through sexual networks of men who have sex with men. Clade I has historically been linked to animal-to-human transmission, often affecting children (and perhaps through household contact, though data on this is thin). Recently, a new variant, clade Ib, has emerged and is spreading through heterosexual contact.

The changing epidemiology and footprint of the epidemic are important and concerning developments. I think the decision to declare a Public Health Emergency is the correct one, and I hope it brings needed attention and resources to the affected countries.

There are still a lot of open questions about modes of transmission and course of clinical illness, so more rapid research is urgently needed to understand how the virus is spreading and who is at risk. Other top priorities include ensuring affected countries have access to vaccines and treatments, adequate diagnostic testing capacity, and the necessary funding to support their response efforts.

In the United States, clade II is still circulating, but activity is much reduced compared to 2022. No cases of clade I have been detected, but if the epidemic does not come under control, we will surely see importations.

Source: WHO