Covid-19 remains widespread, but hospitalisations have dropped significantly, raising questions about the reasons behind this shift. Experts are grappling with the mystery, especially after the emergence of XEC, a new Covid-19 variant that gained prominence in autumn 2024.

XEC, a descendant of the Omicron variant, has raised alarms among virologists due to its potential to evade immunity from previous infections and vaccines. The variant arose through recombination, a process where genetic material from two other variants fused together. Early tests suggested XEC could bypass protection offered by past infections and the latest Covid-19 vaccines, particularly those targeting the older JN.1 and KP.2 variants.

However, despite concerns, the expected surge in hospitalisations following the Thanksgiving holiday in the United States did not materialize. While surveillance testing revealed widespread infection of XEC through wastewater samples, hospitalisation rates remained remarkably low. According to the Centers for Disease Control and Prevention (CDC), hospitalisation rates at the start of December 2024 were just two per 100,000 people, a sharp decline from the previous year’s rate of 6.1 per 100,000.

Peter Chin-Hong, a professor of Infectious Diseases at the University of California, San Francisco, noted that, despite the high levels of Covid detected, few patients are critically ill. “It just shows that regardless of how scary a variant might look in the lab, the environment in which it lands is much more inhospitable,” he explained.

Experts have suggested that Covid-19 in 2025 may have become a milder disease. Common symptoms such as loss of taste and smell are becoming less frequent, and most people now experience mild cold-like symptoms, often mistaken for seasonal allergies. While immunocompromised individuals and the elderly are still at higher risk, Chin-Hong believes that Covid has become much less severe overall.

Despite this, experts caution that Covid-19 remains a persistent threat to public health. The risk of long Covid, while decreasing, still looms for some individuals, and the possibility of more severe variants emerging in the future cannot be ruled out. As a result, health authorities continue to recommend that vulnerable populations receive the latest Covid-19 vaccines, which can offer protection against serious illness, hospitalisation, and death.

Microbiologist Harm Van Backel, co-leader of the Mount Sinai Pathogen Surveillance Program, noted that, despite the emergence of XEC, Covid-19 has contributed relatively little to hospitalisation rates this winter, with other respiratory viruses taking precedence. He attributed the lower hospitalisation rates to more effective treatments and better immunity in the population.

While Covid-19 may have become less invasive, experts caution that the situation remains unpredictable. Long-term effects, such as persistent gastrointestinal infections linked to Covid, are still being studied. Research continues to focus on developing next-generation vaccines and therapies to better control the virus and its potential future evolution.

Our Sun, the central star of our Solar System, is somewhat of an anomaly in the Milky Way galaxy, where binary star systems—pairs of stars that orbit each other—are quite common. However, recent research suggests that the Sun may have once had a companion, a partner it has since lost to time. The big question now is: where did it go?

The Sun, orbiting in one of the Milky Way’s spiral arms, takes about 230 million years to make a full orbit around the galaxy. While it currently drifts alone, the nearest star to the Sun, Proxima Centauri, is located 4.2 light-years away—a distance so vast it would take thousands of years for even the fastest spacecraft to reach.

However, scientists are increasingly recognizing that most stars, unlike the Sun, form in pairs. In fact, binary star systems are so prevalent that some astrophysicists suggest that all stars may have originally formed as binary pairs. This leads to an intriguing question: could our Sun have once been part of such a system, only to lose its companion long ago?

Gongjie Li, an astronomer at the Georgia Institute of Technology, says it is certainly a possibility. “It’s very interesting,” he noted, pointing out that the absence of a companion star likely spared Earth from gravitational disruptions that might have made life on our planet impossible.

The idea that stars form in pairs is supported by recent findings. Sarah Sadavoy, an astrophysicist at Queen’s University in Canada, has shown that the process of star formation often leads to the creation of multiple stars. Her 2017 research indicated that star-forming regions, like the Perseus molecular cloud, preferentially create pairs of stars. However, not all stars in these systems remain together; some break apart within a million years.

If our Sun had a companion star, it likely would have had significant effects on our Solar System’s formation. For instance, Amir Siraj, an astrophysicist at Harvard University, suggests that the presence of such a companion could explain some of the features of the Oort Cloud—a vast, icy region far beyond Pluto. This distant shell of icy objects could have been influenced by the gravitational pull of the Sun’s missing twin, possibly even contributing to the hypothesized existence of Planet Nine, a yet-undiscovered planet in the outer reaches of our Solar System.

While finding our Sun’s companion star may be a difficult task, Konstantin Batygin, a planetary scientist at the California Institute of Technology, believes there may be clues yet to be uncovered. Recent simulations suggest that a binary companion could explain some of the structure of the Oort Cloud and the slight tilt of the Sun’s axis.

Despite the challenges, the idea that our Sun had a companion star raises intriguing questions about the formation of exoplanetary systems. As astronomers continue to explore distant regions of space, they may eventually uncover more evidence of our Sun’s lost twin—offering insights not only into the history of our own Solar System but also into the diverse ways stars and planets come into being across the universe.