Public Health

DURBAN, South Africa — Doctors and nurses at a South African hospital group noticed an odd spike in the number of Covid-19 patients in their wards in late October. The government had slackened its lockdown grip, and springtime had brought more parties. But the numbers were growing too quickly to easily explain, prompting a distressing question.

“Is this a different strain?” one hospital official asked in a group email in early November, raising the possibility that the virus had developed a dangerous mutation.

With no robust system to identify genetic variations of the coronavirus, experts warn that the United States is woefully ill-equipped to track a dangerous new mutant, leaving health officials blind as they try to combat the grave threat.

The variant, which is now surging in Britain and burdening its hospitals with new cases, is rare for now in the United States. But it has the potential to explode in the next few weeks, putting new pressures on American hospitals, some of which are already near the breaking point.