By Carol A. Kemper, MD, FIDSA
Mpox Accelerates in Africa
Source: Ndembi N, Folayan MO, Komakech A, et al. Evolving epidemiology of mpox in Africa in 2024. N Engl J Med. 2025;392:666-676.
In July 2022, the World Health Organization (WHO) declared a Public Health Emergency during the first mpox pandemic, during which > 100,000 mpox cases occurred worldwide. Most of these cases were caused by clade I, which is considered to have greater potential for disease severity and mortality. By May 2023, the WHO declared an end to the pandemic, although that was hardly the end of this infection. More than 10,000 mpox cases were reported in Brazil both in an initial wave of infection from June 2022 through May 2023, followed by a resurgence of cases in September 2023 through January 2024 (see the April 2025 issue of Infectious Disease Alert).
Africa remains a hotbed of mpox infection. From January 2022 to October 2024, an astounding 45,652 laboratory-confirmed cases were reported to the Africa Centres for Disease Control (Africa CDC) from 12 countries, including 1,492 deaths (3.3%). During this period, weekly reported cases steadily increased, nearly doubling the case rate in two years. Six countries reported cases in 2024 for the first time, indicating the infection is spreading across the African continent. As a result, the Africa CDC gathered 20 scientists and clinicians in August 2024 to review the data and recommended a first-ever African Public Health Emergency of Continental Security. Two days later, the WHO declared a second mpox Emergency of International Concern. These declarations stimulate affected countries to focus efforts on identification, contact tracing and containment, and reporting.
The Democratic Republic of Congo (DRC) has been the most affected by the current outbreak; 88% of all African mpox cases in 2024 were reported from the DRC (19,513 cases and 601 deaths). Before the emergency declaration, three-fourths of the DRC cases occurred in six of the 24 provinces; almost half (48%) occurred in children (< 15 years of age). This is in contrast to other African countries, where outbreaks have largely circulated in sex workers or in men who have sex with men. Most cases in the current DRC outbreak are due to clade Ia, while genetic data suggest that clade Ib, which appeared to emerge in 2023 from a non-human host, largely has resulted in sustained transmission among sex workers. Countries that border the DRC also are experiencing clade Ib cases. Clade IIa cases are occurring largely in West Africa.
Most African countries have central laboratory capability for mpox testing, although distribution of test kits and supplies (not to mention transportation back to the lab) remains a problem, especially in more rural areas. Given these problems, it is likely that significant underreporting of cases and deaths is occurring in Africa. Efforts to recognize and contain the mpox infection, especially in the DRC, will be hampered by the ongoing violence in some regions, disruption of social services, and extreme poverty and deprivation, especially given the current lack of funding for education, case detection, and vaccine programs. It is only a question of time before this African endemic becomes another pandemic and risks mpox becoming yet another worldwide sexually transmitted infection, only this one with the potential for death.
Why Does Colonization Become Active C. difficile?
Source: Clement J, Barlingay G, Addepalli S, et al. Risk factors for the development of Clostridioides difficile infection in patients colonized with toxigenic Clostridioides difficile. Infect Control Hosp Epidemiol. 2025;Feb 24:1-7. doi:10.1017/ice.2025.4. [Online ahead of print].
These authors performed a nested case-control study to identify risk factors for the progression from Clostridioides difficile (CD) colonization to active infection (CDI) in hospitalized persons. Based on data demonstrating the benefit of screening in the reduction of CD transmission in the hospital, the University of California Davis Medical Center performs universal screening for CD using perirectal polymerase chain reaction (PCR) for all admissions. They preemptively isolate all patients with CD colonization.
To identify risk factors for progression from colonization to active infection, patients who developed active CDI were matched 1:3 with those who did not. Patients were excluded from the study if they had a previous history of CDI, neutropenia, or hospitalization within 24 hours. Active CDI was diagnosed based on both symptoms of three or more loose stools within 24 hours and a positive CD toxin enzyme immunoassay (EIA) test, pseudomembranous colitis on colonoscopy, or histopathologic evidence of active CDI. Hospital-onset CDI (HO-CDI) was defined as occurring after the first three days of hospitalization.
From 2017 to 2020, 57,468 admissions to the hospital were screened, of whom 2,150 (3.7%) were perirectal PCR-positive for toxigenic CD organism. Among these, 109 patients were diagnosed with CDI, including 69 cases of HO-CDI. The median time to diagnosis of CDI was 7.4 days. The average age was 64 years, and the average hospital length of stay was 11.9 days. All-cause mortality during hospitalization was significantly higher for HO-CDI infection cases compared with controls (15.9% vs. 6.3%, P = 0.011). Bivariate analysis showed that HO-CDI cases were more likely older (> 65 years of age), admitted from healthcare facilities, admitted to the intensive care unit (ICU) at baseline, and hospitalized within the previous six months. They also were more likely to have cirrhosis (17.4% vs. 7.1%, P =0.01), to have diabetes (50.7% vs. 30.2%, P = 0.002), to have malignancy (21.7% vs. 7.9%, P = 0.001), to be immunosuppressed, to have received immunosuppressives prior to hospitalization, to have received antibiotics within the three months prior to hospitalization (76.8% vs. 43.8%, P < 0.001), or to have received “at-risk” antibiotics during the hospital stay (60.9% vs. 23.8%, P < 0.001). Multivariate analysis confirmed that the risk of progression to HO-CDI was significantly associated with cirrhosis, hospitalization within the prior six months, ICU admission, malignancy, and an increased number of at-risk antibiotics. Proton pump inhibitor use was not significantly associated with the progression to CDI.
Most of us would recognize these previously mentioned risk factors for progression to active CDI, with the possible exception of cirrhosis. It is of interest that 70% of the patients in this cohort were admitted from home, although 62% had been hospitalized within the previous six months. Increasingly, CDI is recognized as a community-acquired pathogen. Our facility in Mountain View, CA, similarly screens admissions with perirectal PCR in an effort to preemptively isolate those with colonization and reduce the risk of hospital transmission. Rather than universal screening, we have chosen to focus our efforts on those patients at higher risk for CD colonization, including those with a history of CDI (35% colonized), those receiving dialysis (19% colonized), and those admitted from a skilled nursing facility or long-term acute care (LTAC) facility (14% colonized). Even with this, only 20% to 30% of hospitalized patients who develop HO-CDI had a positive CD PCR on admission, and only ~5% of those with colonization on admission progress to active HO-CDI.
The problem becomes how do we identify that one-in-20 individual out of all of those who are colonized and possibly at risk, who will go on to develop HO-CDI? What is it about that 5% of persons with colonization that puts them at particular risk for progression to active CDI during their hospitalization? If prevention or intervention is to be effective, we need a better way to identify that individual. It does not make sense to give everyone at risk preemptive oral vancomycin if only 5% might benefit.
Avian Influenza in Felines Exposed to Dairy Workers
Source: Naraharisetti R, Einberg M, Stoddard B, et al. Highly pathogenic avian influenza A (H5N1) virus infection of indoor domestic cats within dairy industry worker households — Michigan, May 2024. MMWR Morb Mortal Wkly Rep. 2025;74(5):61-65.
In May 2024, two domestic cats developed severe respiratory and neurologic illness and died from highly pathogenic avian influenza (HPAI) A/H5N1 virus. Each cat was living in the home of a dairy worker, neither of whom worked on farms recognized to have a problem with HPAI A (H5N1).
The first cat was a 5-year-old domestic short hair who reportedly was an exclusively indoor cat. She was one of three cats in the household. She developed progressive respiratory and neurologic illness over a four-day period, beginning with loss of appetite, lethargy, ataxia, and hiding behavior, and then evolved into frank encephalitis with cranial nerve impairment, abnormal motor function, and jaw swelling. The cat was brought to a local vet and given subcutaneous antibiotics, with transient improvement. On the fourth day of illness, the cat was brought to the Michigan State University Veterinary Medical Center (MSU VMC), where she was euthanized. Specimens from brain and nasal swabs were positive for HPAI A (H5N1), and genetic sequencing revealed clade 2.3.4.4b, genotype B3.13, similar to that circulating in Michigan cattle at the time.
A second cat, a 6-month-old Maine Coon, developed a one-day illness with similar features, including anorexia, lethargy, facial swelling, progressive obtundation and cranial nerve abnormalities, and abnormal motor function. This also was an indoor animal. The cat was brought to the MSU VMC and quickly died within 24 hours. Nasal swabs were positive for influenza A, subsequently confirmed as HPAI A (H5N1) with the same genotype.
Investigation of both households was conducted. The first cat lived with two other cats — one of which developed some signs of illness four days after the onset of illness in its feline companion, but the owner declined to submit nasal swabs for testing, and the cat ostensibly recovered. The third cat was brought into the facility for testing and was negative. The owner reported that he worked at a local dairy not known to be affected by HPAI A (H5N1), and he did not have direct contact with the farm animals. He removed his clothes and boots outside the home. He had experienced one day of vomiting and diarrhea several days before his cat’s illness. He declined testing, although three other household members (one adult and two adolescents) agreed to testing and were negative.
The owner of the second cat also declined testing. He also worked at a dairy farm not known to be at risk, where he directly worked with unpasteurized milk without wearing personal protective equipment (PPE), and sustained frequent splashes to his face, eyes, and clothing. He also transported milk to other farms that were known to be affected by HPAI A (H5N1). Two days prior to his cat’s illness, he had eye irritation but no other symptoms. He did not remove his clothing before entering his home, and the cat reportedly rolled around in his clothes. A second cat in the household did not roll around in the clothes and remained asymptomatic, and nasal swabs were negative.
A total of 24 veterinary staff workers were potentially exposed to the two animals. Varying levels of PPE were used, including possibly initial facemasks and later N95 masks when in contact with the first cat. Eighteen of these individuals were contacted and monitored. Seven individuals reported some signs or symptoms of illness, and five individuals tested negative. Because exposure was considered limited, post-exposure prophylaxis was not offered.
HPAI A (H5N1) infection in cats and, more rarely, dogs, has been reported. The source for infection in these two domestic felines is not known, but transmission presumably occurred from the owners or the owners’ clothing/shoes. How contagious the cats might have been is not known, although transmission from infected cats and dogs is considered extremely low risk. Fomite transmission of influenza A is a theoretical concern, and studies demonstrate infectious influenza on hard surfaces for up to 24-48 hours and on soft surfaces (i.e., clothing and tissues) for up to six to eight hours.
Carol A. Kemper, MD, FIDSA, is Medical Director, Infection Prevention, El Camino Hospital, Palo Alto Medical Foundation.
Mpox Accelerates in Africa; Why Does Colonization Become Active C. difficile? Avian Influenza in Felines Exposed to Dairy Workers
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