Viral waves

This graphic shows the rise of the latest Omicron coronavirus variants — BA.4 and BA.5 — alongside spikes in earlier SARS-CoV-2 variants. BA.4 and BA.5 are driving a surge of COVID-19 cases in South Africa, where researchers identified the original Omicron variant, and they might set off fresh waves elsewhere. As our News story reports, the evolution of SARS-CoV-2 could come to resemble that of other respiratory infections. Immune-evading mutations in circulating variants, such as Omicron, could combine with dips in population-wide immunity to become the key drivers of periodic waves of infection.

Omicron's new identities: Two charts showing rising cases of COVID-19 in South Africa and the spread of Omicron variants.

Source: Top, Our World in Data; Bottom,

The United States, post Roe

This map shows the potential repercussions if the verdict of the 1973 case Roe v. Wade is overturned in the United States. A leaked draft opinion suggests that the US Supreme Court might be about to end the precedent set by the landmark decision that ensured access to abortion. If this happens, 25 US states are poised to outlaw most abortions, a scenario that could mean roughly 18 million people of child-bearing age would have to travel more than 200 miles (322 kilometres) for the procedure, a journey that many would be unable to make. This Editorial argues that such a decision would fly in the face of an overwhelming body of evidence from economists and reproductive- and public-health researchers about the dire and unequal impact this ruling would have.

If roe is overturned: Map of the United States showing distance to nearest abortion facility and facilities likely to close.

Source: Caitlin Myers/Middlebury College

Domino effect in artificial hairs

These wobbly-looking skyscrapers are illustrations of artificial cilia. Cilia are the microscopic hairs that grow on the surface of some single-celled creatures and, by beating rhythmically, propel them through fluid. A paper this week in Nature revealed artificial cilia that produce complex, collective beating patterns when powered by light.

The team incorporated molecular machines, which flip back and forth in response to light, into a liquid-crystalline polymer material (a). When light shines through the material, it activates the machines, which change shape and deform the illuminated area. This forces the cilium as a whole to bend and twist (b). Arrays of cilia exhibit collective motion through shadowing effects: one cilium blocks light from reaching its neighbour, but as soon as it starts beating, light shines on the neighbouring cilium, which, in turn, starts moving. This creates a domino effect through the array.

figure 1