The strains, XFB, dubbed Stratus, and NB.1.8.1, known as Nimbus, are fueling a surge in infections, with cases spiking specifically in the northeast last month in the US and doubling in the UK since August. In the US, nationwide Covid wastewater levels, used to measure the community spread of a virus, are ‘moderate,’ according to the CDC, but four states are recording ‘very high’ levels and levels in the northeast region are on the rise. The new strains can also cause more familiar Covid complaints such as headaches, coughing, fatigue and a runny or blocked nose. Experts stress they are no more dangerous than earlier versions, but genetic mutations mean they spread more easily. Should the world prepare for a new pandemic ?

