Low-level mpox transmission continues in many parts of the world, with Africa, Europe, and the Americas reporting the largest portion of recent cases, the World Health Organization (WHO) said in a monthly situation update yesterday, which covers cases reported in March.

Adding a caveat that a decline in surveillance may underestimate infections, the WHO said 466 new cases, 3 of them fatal, were reported in March. In Africa, the Democratic Republic of the Congo (DRC)—experiencing an outbreak of a novel clade 1 virus—reported the most cases.

Ten countries reported case rises in March, with the Republic of Congo reporting the largest rise in Africa. Other hot spots were the United Kingdom, Puerto Rico in the United States, and Vietnam.

The WHO said the risk is high for the DRC's general population and moderate for countries that have historically reported mpox infections and for men who have sex with men, gender-diverse people, and sex workers. The general population risk for countries that haven't experienced earlier outbreaks is low.

Over the past 6 months, monthly cases have fluctuated between 400 and 1,000 cases, with most reported in the Americas, Europe, and Africa. Though sexual encounters are the most common mode of transmission, patterns in Africa are more diverse and include the zoonotic route.

Advisers discuss mpox vaccine issues

WHO vaccine advisers met in March, and they said populations to consider for vaccination include adults and children in geographic areas with documented exposure risks, people with multiple sexual contacts, health workers with repeated exposure, and known contacts of infected people. 

The group called for strong measures to promote mpox and vaccine research in Africa, along with equitable access to vaccines. The committee expects to release its final recommendations on mpox  immunization in May.

A new meta-analysis of 16 studies reveals that, for pre-exposure prophylactic vaccination (PrEP, which is used for disease prevention), the vaccine effectiveness (VE) of one Jynneos dose ranged from 35% to 86%, and VE for  post-exposure prophylactic vaccination ranged from 78% and 89% for one dose.

The findings are published on the preprint server medRxiv and represent the most current evidence of vaccine protection offered by Jynneos, Bavarian Nordic's two-dose vaccine used for the past 2 years to fight a global mpox outbreak. The study has not yet been peer-reviewed.

As of February 2024, more than 94,000 confirmed mpox cases have been documented in 117 countries in an outbreak that mostly affected men who have sex with men. Jynneos, also called MVA-BN, can be administered prophylactically either before or after exposure to confirmed mpox cases in two doses, administered 28 days apart.

The analysis included data from six countries: the United States, Canada, Spain, the United Kingdom, Israel, and the Netherlands.

Different administration routes protective

In eight studies, the VE of one dose of MVA-BN administered as PrEP was 35% to 86%, while five studies reported two-dose adjusted VE estimates ranging from 66% to 90%.

Two studies also provided VE estimates for administering Jynneos with intradermal injection or subcutaneously, and found similar ranges of protection regardless of administration route: 80% (95% confidence interval [CI], 23% to 95%) for intradermal administration, 89% (95% CI, 56% to 97%) for subcutaneous administration, and 87% (95% CI, 69% to 95%) when administered via a combination.

The authors conclude that the findings "demonstrated the effectiveness of one or two doses of MVA-BN against symptomatic mpox infection in outbreak settings."

At least 12 people in California and Washington state have been sickened and 7 people hospitalized in an Escherichia coli O157 outbreak traced to Gibson Farms organic walnuts that are sold in 19 states, the Centers for Disease Control and Prevention (CDC) said in a food safety alert yesterday.

Two patients developed hemolytic uremic syndrome, a serious and potentially fatal kidney condition. The CDC said in a news release, "Almost all sick people purchased organic walnuts from bulk bins in food co-ops or natural food stores in California and Washington." Two people bought bulk walnuts from the same store.

Company recalls bulk walnuts

In a recall notice yesterday, the Food and Drug Administration (FDA) said Gibson Farms has voluntarily recalled the implicated walnuts. "Gibson Farms Organic Light Halves and Pieces shelled walnuts were sold in bulk boxes in Net Wt. 25 lbs quantities and can be identified by lot 3325-043 & 3341-501 with expiration dates 5/21/25 & 6/7/25."

The agency added, "A full investigation is currently under way to determine the potential source of the contamination."

The CDC said the nuts were distributed to natural food and co-op stores in Alaska, Arkansas, Arizona, California, Colorado, Hawaii, Idaho, Kansas, Louisiana, Montana, Nebraska, New Mexico, Nevada, Oregon, South Dakota, Texas, Utah, Washington, and West Virginia. The FDA has posted a list of stores that sold the walnuts.

Gibson Farms, Inc, is headquartered in Hollister, California.

First patient fell ill on February 1

The 12 patients—6 in California and 6 in Washington—range in age from 6 to 84 years, with a median age of 57. Eight are female. Of 10 patients who reported racial information, 9 are White and 1 is Black.

Illness-onset dates range from February 1 to April 4. No deaths have been reported.

"The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses," the CDC said.