The highly mutated SARS-CoV-2 BA.3.2 variant, which has been reported by at least 23 countries as of February 11, has been detected in nasal swabs collected from four US travelers, clinical samples from five patients, three airplane wastewater samples, and 132 wastewater surveillance samples from 25 states, per a study published last week in Morbidity and Mortality Weekly Report.

First identified in a respiratory sample in South Africa in November 2024, the strain has roughly 70 to 75 substitutions and deletions in the gene sequence of its spike protein relative to the JN.1 variant and its descendant, LP.8.1, the antigens used in the latest COVID-19 vaccines. 

“BA.3.2 represents a new lineage of SARS-CoV-2, genetically distinct from the JN.1 lineages (including LP.8.1 and XFG) that have circulated in the United States since January 2024,” wrote the authors, led by Centers for Disease Control and Prevention (CDC) researchers. The CDC uses digital public health surveillance to monitor SARS-CoV-2 variants around the world.

30% prevalence in 3 European countries

Detections of BA.3.2 began rising in September 2025. The first US identification of the strain was on June 27, 2025, through the CDC’s Traveler-Based Genomic Surveillance program in a person traveling to the United States from the Netherlands. 

Continued genomic surveillance is needed to track SARS-CoV-2 evolution and determine its potential effect on public health.

From November 2025 to January 2026, weekly BA.3.2 detections increased to about 30% of sequences in Denmark, Germany, and the Netherlands. The first US instance of BA.3.2 in a clinical specimen was documented on January 5, 2026. As of February 11, the strain’s prevalence among 2,579 total genetic sequences in national surveillance collected starting on December 1, 2025, was 0.19%.

“Because many countries have limited genomic detection and surveillance capacities, these detections likely underrepresent the actual geographic extent of spread,” the researchers wrote. “Phylogenetic analyses have identified the emergence of two BA.3.2 sublineages (BA.3.2.1 and BA.3.2.2), indicating ongoing viral evolution.”

As BA.3.2 mutations in the spike protein could reduce protection from a vaccination or infection, “continued genomic surveillance is needed to track SARS-CoV-2 evolution and determine its potential effect on public health,” they added.

Data show that young, healthy people have no additional risk of sudden death if they are vaccinated against COVID-19, contrary to myths that continue to circulate widely on social media.

In fact, healthy adolescents and young adults vaccinated against COVID-19 were 43% less likely to experience sudden death than non-vaccinated people, according to a Canadian case-control study published last week in PLOS Medicine.

Researchers focused on Ontario residents ages 12 years to 50 years old. None had chronic conditions that increase the risk of death from COVID-19.

Sudden death in this population was incredibly rare, occurring in 4,806 people––or 0.08%––of the nearly 6.4 million people whose medical records were included in the study. 

The study authors matched each person who died to five living people based on age, sex, region, and neighborhood income. Researchers defined a death as one that occurred outside the hospital or within 24 hours of arriving at a hospital with a final diagnosis of cardiac arrest from April 1, 2021, to June 30, 2023. 

The researchers found no increased rate of sudden death in people within six week of the first, second, or third vaccine dose.

Findings add to growing evidence of vaccine safety

The new research confirms earlier studies that also have found no link between COVID vaccinations and sudden death in young people. 

A study published in JAMA Network Open in 2025, for example, found no increased risk of sudden cardiac arrest or sudden death in young athletes during or after the pandemic. 

Research published in 2024 also found no link between mRNA COVID-19 vaccination and sudden cardiac death. The study, which appeared in the US Centers for Disease Control and Prevention’s flagship publication, Morbidity and Mortality Weekly Report, examined death certificates and immunization records of previously healthy young adults in Oregon.

Sepsis is a fast-moving, life-threatening condition that occurs when the body overreacts to an infection, sometimes causing permanent organ damage and death.

A new study, published yesterday in JAMA, identified sepsis in 1.3% of hospitalized US children ages one month to 17 years old. The study, which included data from nearly four million admissions from 2016 through 2023, found that 10% of children with sepsis died while in the hospital. 

Overall, 18% of deaths in hospitalized children were related to sepsis, the study showed. Based on those rates, researchers calculated that more than 18,000 cases of sepsis and 1,800 deaths in 2022 among children in this age group.

Findings based on electronic health records

In an accompanying editorial, physicians from Australia, Singapore and Switzerland commended the study authors for developing a standardized way to measure sepsis cases and deaths in children. Previous reports have been based on diagnostic codes, which can vary by hospital and over time. Annual estimates of pediatric cases have varied dramatically, ranging from 33,000 illnesses a year to 75,000.

The new study is based on electronic health records, including laboratory results, use of antibiotics, and markers of organ dysfunction, such as the use of mechanical ventilation.

Children with sepsis, which can cause permanent disabilities, stayed in the hospital an average of 24 days, far longer than the average length of stay of four days. About 79% of children with sepsis were treated in intensive care units, compared to fewer than 1% of other children.

“These findings underscore the substantial burden of pediatric sepsis and its major contribution to childhood morbidity and mortality,” the study authors wrote.

US maternal syphilis case detection rose 26% in the first quarter after screening opportunities were mandated in the third trimester of pregnancy and at delivery, although the confidence intervals were very wide, and the effect fell off and became insignificant in the next year, Harvard researchers write in JAMA Health Forum.

For the study, which included 16.3 million live births and 20,961 syphilis cases from 2012 to 2022, the investigators analyzed birth certificate data from 33 states from 2012 to 2022. They compared maternal syphilis case detections in Arizona, Georgia, Louisiana, and Michigan, all of which enacted expanded mandates for third-trimester and/or delivery screening, with 29 control states without such mandates during this period. 

All four states required offering pregnant women third-trimester screening, while three mandated that high-risk patients be offered testing again at delivery, and one required universal screening at delivery. To determine whether expanded mandates were tied to changes in screening uptake, the team analyzed hospital release records from Georgia.

“Congenital syphilis rates in the US have surged nearly 12-fold over the last decade (from 8.7 to 105.8 cases per 100 000 live births between 2013 and 2023) since reaching historically low rates in the early 2000s,” the researchers wrote. “Transmitted from mother to child during pregnancy, congenital syphilis increases the risk of stillbirth, neonatal death, low birth weight, and infant death, and can confer lifelong medical complications.”

Complementary efforts needed

Expanded screening mandates were linked to a 26% (95% confidence interval [CI], 3% to 53%) increase in maternal syphilis case identification in the first quarter of enactment. But the increase attenuated and was no longer significant within one year (11%; 95% CI, −17% to 48%).

Congenital syphilis increases the risk of stillbirth, neonatal death, low birth weight, and infant death, and can confer lifelong medical complications.

The waning impact may reflect falling adherence to mandates among expansion states, the study authors said. “In this study, expanded prenatal syphilis screening mandates may improve syphilis case detection in the near-term but are unlikely to have sustained impact without complementary efforts, such as those that facilitate clinician adherence and ensure patient access to and completion of treatment,” they wrote.