After 8 days with no new cases, Rwanda's health ministry yesterday reported 1 new illness, raising the outbreak total to 63 cases, as the number of deaths held steady at 15. Two patients are still in treatment, and 46 have recovered.

At a media briefing with the Africa Centre for Disease Prevention and Control (Africa CDC), Rwanda Minister of Health Sabin Nsanzimana, MD, PhD, said the latest patient is a healthcare provider who works in the Marburg treatment center.

Patient had been vaccinated just days before

Though the man tested positive, he is doing well and doesn't have the usual Marburg symptoms. The patient had been vaccinated against Marburg a few days ago, and it's not clear if he was exposed to the virus before or after vaccination. 

The patient had no contacts outside the Marburg treatment center and had been living in a setting where the infection prevention and control protocol was high.

Nsanzimana said Rwanda has gone 10 days with no new Marburg deaths. He added that the overall picture is encouraging, though officials can't rule out other contacts reaching the symptomatic phase. The number of contacts under monitoring continues to decrease. "It's not yet over, but we have a great trend."

New genomic surveillance data published today in Morbidity and Mortality Weekly Report show that JN.1 and its descendants have been the most common SARS-CoV-2 variants in 2024, and they're still evolving.

The genomic surveillance was conducted by the Centers for Disease Control and Prevention's national SARS-CoV-2 genomic surveillance program, which previously detected both the Delta and Omicron variants. 

The new report covers detections from May 2023 through September 2024, from which researchers analyzed 208,357 SARS-CoV-2 sequences from 56 US jurisdictions.

In the summer of 2023, the authors write, multiple Omicron XBB descendants, including EG.5-like lineages, FL.1.5.1-like lineages, and HV.1 lineages reached more than 10% prevalence in the United States. 

JN.1 increased in winter of 2023

By the winter of 2023, however, JN.1 increasingly took hold. 

The JN.1 variant emerged in the United States and rapidly attained predominance nationwide.

"The JN.1 variant emerged in the United States and rapidly attained predominance nationwide, representing a substantial genetic shift," the authors write. "Surges in COVID-19 cases occurred in winter 2024 during the shift to JN.1 predominance.”

More surges were seen in the summer of 2024, the authors write, when cocirculation of JN.1 descendant lineages with identical substitutions, including the S31 deletion, R346T, and F456L emerged. These substitutions cause immune escape and increased transmissibility. 

"Continued monitoring to determine whether this pattern of divergent variant emergence followed by subsequent stepwise evolutionary changes continues will be important for updating COVID-19 vaccines and anticipating surges in COVID-19 activity," the authors conclude. 

Today in Morbidity and Mortality Weekly Report (MMWR), researchers from the US Centers for Disease Control and Prevention (CDC) describe two cruise-ship outbreaks of Legionnaires' disease tied to private balcony hot tubs.

From November 2022 to June 2024, 12 cases of Legionnaires' disease were reported to the CDC among travelers on two cruise ships, with eight on ship A and four on ship B. The ship A outbreak was the largest cruise Legionnaires' disease outbreak that the CDC had investigated since 2008. Legionnaires' is a serious type of pneumonia caused by Legionella bacteria.

Private hot tubs subject to less-stringent requirements

CDC investigators interviewed the ill travelers and analyzed environmental samples, concluding that private balcony hot tubs were the most likely source of the bacteria.

Hot tubs offer favorable conditions for Legionella growth and transmission when maintained and operated inadequately, regardless of location.

Hot tubs on ship A had been operating for months under conditions conducive to Legionella growth, which included maintaining a water temperature of 77°F to 113°F for multiple days without draining or residual disinfectant. 

Some tubs on this ship were located on decks only one floor above or below common outdoor amenities. The CDC noted that previous investigations have shown that hot tubs in private areas can spread pathogens via aerosols to common areas and expose people in those areas—even those who don't use the tubs themselves.

"Hot tubs offer favorable conditions for Legionella growth and transmission when maintained and operated inadequately, regardless of location," the researchers wrote. "Private hot tubs on cruise ships are not subject to the same maintenance requirements as are public hot tubs in common areas." 

The investigators recommend that cruise-ship water-management staff inventory and evaluate private balcony hot tubs and adapt maintenance and operations procedures used for public hot tubs for use in private outdoor hot tubs. Both cruise lines modified the operation and maintenance of the private hot tubs by removing the heating elements, draining water between uses, and cleaning and hyperchlorinating them more often.

Ship A also removed filtration elements from the tubs. Sampling is ongoing on both ships.

A study of US adults who had community-acquired pneumonia (CAP) but were otherwise healthy found that broad-spectrum antibiotics were associated with increased risks of adverse drug events (ADEs), researchers reported yesterday in Clinical Infectious Diseases.

Using national data from a large insurance database, researchers from Washington University School of Medicine in St. Louis performed an active comparator new-user study to estimate the comparative risk of several individual ADEs between different outpatient antibiotic regimens for CAP among otherwise healthy, non-elderly adults. As the study authors note, uncertainty about the risks and benefits of different antibiotic regimens has resulted in a wide variation in antibiotic prescribing for CAP in outpatient settings, even though guidelines generally recommend narrow-spectrum agents when possible.

Increased risk of several ADEs

The researchers included 145,137 adults aged 18 to 64 who were diagnosed as having CAP from July 1, 2007, through November 30, 2019, and evaluated CAP-related antibiotic regimen and ADEs experienced 2 to 90 days after treatment. Fifty-two percent of patients received narrow-spectrum antibiotics (44% macrolide, 8% doxycycline) and 48% received broad-spectrum antibiotics (39% fluoroquinolone, 7% beta-lactam, 3% beta-lactam plus macrolide). The most common ADEs were nausea/vomiting/abdominal pain, rash/urticaria, non–Clostridioides difficile diarrhea, and vulvovaginal candidiasis/vaginitis

Compared with macrolide monotherapy, each broad-spectrum antibiotic was associated with increased risk of several ADEs. For example, beta-lactam was associated with increased risk of nausea/vomiting/abdominal pain (risk difference [RD] per 100, 0.32; 95% confidence interval [CI], 0.10 to 0.57), non–C difficile diarrhea (RD per 100, 0.46; 95% CI, 0.25 to 0.68), and vulvovaginal candidiasis/vaginitis (RD per 100, 0.36; 95% CI, 0.09 to 0.69). Doxycycline largely conferred similar risk of ADEs as macrolide monotherapy. 

The authors say the results of the study add to accumulating evidence suggesting that efforts to shift prescribing from broad-spectrum to narrower-spectrum agents may prevent ADEs.

"Ultimately, knowledge about antibiotic-related harms can help patients, prescribers, and stewardship programs make judicious decisions about antibiotic utilization," they wrote.