A study of two large, integrated health systems suggests that outpatient Clostridioides difficile infection (CDI) may be underdiagnosed, researchers reported today in Open Forum Infectious Diseases.

In a retrospective study of adult members of Kaiser Permanente Southern California and Kaiser Permanente Northwest, researchers identified 777,533 medically attended diarrhea (MAD) episodes among 592,877 people from 2016 through 2021. The researchers targeted patients with MAD episodes because they haven't been well described and are believed to contribute to a reservoir of undiagnosed CDI cases in the community because these patients don't always get tested for CDI.

Of the 777,533 MAD episodes, stool specimen testing was ordered for 37% but only 12.1% were tested for CDI. Testing for CDI was most frequent among patients aged 70 years and older and least common for patients ages 18 to 49. The outpatient incidence rate of CDI was 51.0 per 1,000 patient-years over the entire study period, dropping from 58.2 in 2016 to 45.7 in 2021. Incidence increased with age and was highest among women, non-Hispanic White patients, and those with underlying comorbid conditions.

No recent antibiotic use, hospitalization for many cases

The strong majority of outpatient CDI cases (84.1%) were community-associated (no hospitalization 12 weeks prior to the index case), and less than half (44.1%) received an antibiotic in the 30 days before the index date. Roughly one third of patients with outpatient CDI did not receive treatment or have frequent contact with the healthcare system in the year following their infection.

"While lower-than-expected rates of CDI treatment and relatively low levels of healthcare utilization in the one year following outpatient CDI diagnosis indicate short illness duration and limited impact on the healthcare system, the low frequency of C. difficile testing among patients presenting with diarrhea indicates that outpatient CDI may be underdiagnosed, and the incidence of outpatient CDI may be higher than appreciated," the study authors wrote.

The authors add that the lack of recent antibiotic use or hospitalization among many of the identified outpatient CDI cases suggests other factors, such as transmission within households, could be contributing to the occurrence of CDI in the general community.

Just months after the spread of avian flu was first confirmed in Antarctica's wild birds, the virus has now been detected for the first time in the region's mammals, which include elephant seals and fur seals on the island of South Georgia.

In a statement, the South Georgia and South Sandwich government said following the detection of the virus in wild birds in October, scientists spent 3 weeks aboard a British navy vessel visiting affected islands and collecting samples from dead mammals and birds. Sequencing has identified the H5N1 strain in samples from the two seal species, as well as birds, including brown skuas, kelp gulls, and Antarctic terns.

"The available genomic surveillance data continues to suggest no widespread mammalian adaptation of the virus. There remains no increased risk to human health—the risk of human infection with H5N1 remains very low," the government said.

Animal health groups have warned about the risk of virus spread to Antarctica's wildlife populations, with 48 bird species and 26 mammal species living in the region, often in dense colonies. The latest detections follow further southward spread of the virus, raising worries that the virus could jump to Oceania.

Countries report more outbreaks in poultry, wild birds

Elsewhere, European countries and Japan reported more highly pathogenic avian flu detections in wild birds and poultry, according to the latest notifications from the World Organization for Animal Health. In Europe, Germany reported an outbreak at a poultry farm in Bavaria state, and Denmark reported more detections in wild birds from six locations. And in Japan, animal health officials reported the H5N5 strain in a large-billed crow found dead in Hokkaido prefecture.

The University of Oxford today announced the launch of the first human trial for its candidate ChAdOx1-based Nipah virus vaccine, which was developed by scientists at the school's Pandemic Sciences Institute.

In a statement, Oxford said the phase 1 trial includes 51 adults ages 18 to 55 years old. Researchers will conduct the trial over the next 18 months, with the next phase expected to take place in a country affected by Nipah virus. The Coalition for Epidemic Preparedness Innovations (CEPI) has supported the development of Oxford's Nipah virus vaccine, along with three other candidates, including one from  Massachusetts-based Public Health Vaccines and others from Auro Vaccine and PATH and the University of Tokyo.

Also, an mRNA Nipah vaccine candidate from Moderna is in clinical trials.

Nipah virus, spread by fruit bats, can infect both humans and livestock and can spread person-to-person. People can also contract the virus from drinking palm sap or eating fruit contaminated with bat urine, droppings, or saliva. The disease has a high case-fatality rate, and currently there are no specific treatments or vaccine. CEPI and the World Health Organization have designated Nipah virus as a high-priority pathogen.

Following Argentina's report in December of a rare human Western equine encephalitis (WEE) case, its first in more than two decades, the number of infections has risen to 21, the Pan American Health Organization (PAHO) said yesterday in an update.

Also, as of January 9, health officials have reported 338 outbreaks in animals across Argentina, along with 36 animal outbreaks in Uruguay.

So far, 91 suspected cases have been reported, of which 21 were confirmed. Eleven were from Buenos Aires province, with illnesses also reported from Santa Fe (8), Entre Rios (1), and Santiago del Estero (1) provinces. One of the cases was fatal. All but two of the patients are male, and their ages range from 9 months to 75 years, with most of the cases in people ages 50 and older. The most common symptoms were sudden fever onset, headache, vomiting, and mental confusion.

All patients were hospitalized, and eight needed intensive care unit treatment. Eleven remain hospitalized, and nine have been discharged. Of seven patients with exposure histories, three were veterinarians, two were construction workers, and two had taken part in recreational activities.

Birds are the main hosts of the virus, which can pass the disease to humans and animals through infected mosquitoes. People who work or play outdoors in areas where the virus is endemic or is causing outbreaks in animals are at higher risk of infection.