Southern Hemisphere flu activity is winding down, and data show that the 2024 season was similar to the region’s earlier flu seasons, a reminder that the virus can cause significant public health impact, the US Centers for Disease Control and Prevention (CDC) said in an overview yesterday.

Though it's important to consider Southern Hemisphere flu activity ahead of the upcoming US flu season, the CDC emphasized that patterns there don't always predict how the season will unfold in the United States. Differences in predominant flu viruses and population immunity can contribute to regional variations, it added.

Mix of subregional flu patterns

In the Southern Hemisphere, flu activity this season varied by virus strain, severity, and timing. In South America, H3N2 was the main strain, and Argentina, Chile, and Uruguay had an early start to their seasons. Chile's activity was very high, and Chile, Ecuador, and Uruguay had high levels of severe disease.

In contrast, H1N1 was dominant in the African region, with Zambia reporting an early start to the season and very high levels of illness and severe disease. Activity continues—now mostly from influenza B—in South Africa and Zambia.

H3N2 was predominant in the Oceania region. The timing of Australia's season was similar to pre-COVID years and similar to its 2023 flu season. Flu activity reached the moderate level and has been decreasing in recent weeks, though several areas are seeing upward trends.

The Southern Hemisphere's flu season typically runs from April through September, but it can sometimes extend into October or November, the CDC said.

"Vaccination remains the best defense against flu and even if vaccination does not prevent the risk of flu entirely, it can help reduce the severity of flu illness in people who get flu despite being vaccinated," the CDC said "In the United States, September and October are generally good times to be vaccinated against flu."

An analysis of veterinary data from Germany found that about 12% of Escherichia coli isolates from the country's dogs and cats are resistant to third-generation cephalosporins, researchers reported yesterday in PLOS One.

In the study, a team led by researchers from Germany's Institute of Veterinary Epidemiology and Biostatistics analyzed antimicrobial susceptibility test results obtained from 3,491 veterinary practices in Germany (33% of all practices nationwide) from 2019 through 2021 through GERM-Vet, Germany's monitoring system for resistant pathogenic bacteria in animals. Out of 175,171 samples, they evaluated 25,491 E coli strains for resistance to several antibiotic classes, focusing on cefovecin, the only third-generation cephalosporin approved for veterinary use. 

Third-generation cephalosporin-resistant E coli is considered a significant health threat in both people and animals, and the study authors note that cefovecin resistance can be reasonably compared to resistance to other third-generation cephalosporins. Third-generation cephalosporin-resistant E coli in companion animals is a particular concern because of the potential for transmission to owners.

"Due to the close contact between pet animals and their owners, information on resistance-carrying pathogens in companion animals is crucial for human health as well," the study authors wrote. "Knowledge about the occurrence and distribution are needed to gain further understanding and contribute to the One Health aspect of AMR [antimicrobial resistance]."

Data highlight need for integrated AMR surveillance

The proportion of E coli isolates that were resistant to cefovecin was 11.6%, with a similar proportion found in dogs (11.6%) and cats (11.7%). But there was notable local variation, with some regions showing resistance proportions around 15%. In addition, cefovecin-resistant E coli showed higher resistance levels to other antibiotics, specifically 30% for trimethoprim-sulfamethoxazole, 28% for chloramphenicol, 18% for enrofloxacin, and 14% for gentamicin.

The authors acknowledge that more research is needed to determine how often third-generation cephalosporin-resistant E coli is exchanged between pets and their owners, but they say the findings demonstrate the importance of integrated AMR surveillance.

"Accurate knowledge of antibiotic resistance in animal pathogens is crucial for the optimal use of antibiotics and benefits human and animal health," they concluded.

Data collected from hospitals in South Africa's third most populous province highlight the patients who are bearing the burden of rising rates of carbapenem-resistant Enterobacterales (CRE) in the country, researchers reported yesterday in PLOS One.

Using routine clinical and laboratory datasets, researchers from Stellenbosch University analyzed all CRE episodes (including clinical episodes and carriage) at hospitals in Western Cape province from 2016 through 2020. With CRE becoming an increasing problem at hospitals across the country but little local data on it, they wanted to describe the epidemiology of CRE carriage and infection, examine patient demographics and resistance phenotypes, and identify factors associated with mortality.

A total of 2,242 CRE episodes (70.5% clinical episodes and 29.5% carriage) were identified over the study period. Among the 2,281 CRE isolates identified, the most common species were Klebsiella spp (72.1%), Enterobacter cloacae (15.1%), and Escherichia coli (5.5%). Affected patients were mostly male (52%) and had a median age of 31 years. Most CRE episodes occurred in hospitalized patients (93%) and were recorded in central hospitals (70%).

The proportions of CRE isolates that were non-susceptible to imipenem and meropenem were 77.6% and 74.6%, respectively, and resistance to other beta-lactam antibiotics exceeded 98%. 

Factors associated with death

Among the 2,109 CRE episodes with available outcome data, 20.4% of patients died; crude in-hospital mortality rates were significantly higher for CRE clinical episodes (26.9%) than for CRE carriage episodes (6.4%). 

Factors that showed a statistically significant association with in-hospital mortality were female sex (adjusted odds ratio [aOR], 1.40; 95% confidence interval [CI], 1.09 to 1.56)], adult patients (aOR, 1.76; 95% CI, 1.20 to 2.57), CRE isolation from a sterile specimen (aOR, 0.41; 95% CI, 0.32 to 0.53), and more than 3 days between hospital admission and specimen collection (aOR, 1.56; 95% CI, 1.11 to 2.18).

"It is important to identify these factors to improve patient outcomes, to guide treatment strategies, enhance infection prevention and control (IPC) measures and to address the broader public health and economic implications of CRE infections," the study authors wrote. "This ultimately impacts the greater fight against [antimicrobial resistance] and the improvement of health care."