SYDNEY, Australia — One case. One young security guard at a quarantine hotel who tested positive for the coronavirus and experienced minor symptoms.

That was all it took for Perth, Australia’s fourth-largest city, to snap into a complete lockdown on Sunday. One case and now two million people are staying home for at least the next five days. One case and now the top state leader, Mark McGowan, who is facing an election next month, is calling on his constituents to sacrifice for each other and the nation.

As Covid-19 took hold over the last year, hospitals and nursing homes used and reused scarce protective equipment — masks, gloves, gowns. This desperate frugality helped prevent the airborne transfer of the virus.

But it also appears to have helped spread a different set of germs — drug-resistant bacteria and fungi — that have used the chaos of the pandemic to grow opportunistically in health care settings around the globe.

These bacteria and fungi, like Covid-19, prey on older people, the infirm and those with compromised immune systems. They can cling tenaciously to clothing and medical equipment, which is why nursing homes and hospitals before the pandemic were increasingly focused on cleaning rooms and changing gowns to prevent their spread.

That emphasis all but slipped away amid an all-consuming focus on the coronavirus. In fact, experts warn, the changes in hygiene and other practices caused by the Covid-19 fight are likely to have contributed to the spread of these drug-resistant germs.