A rise in antibiotic-resistant bloodstream infections threatens to bring "another crisis" as COVID restrictions continue to ease, experts have warned.
Drug-resistant infections fell in 2020 for the first time since 2016, but they are likely to rise again as social mixing increases, and when restrictions are dropped, the UK Health Security Agency (UKHSA) said.
Experts warned the resistance to the drugs "has been described as a hidden pandemic" and called on people to "act responsibly" and to carry out measures "as simple as thorough handwashing".
Antibiotics can be prescribed to treat coughs, earaches and sore throats, but are also vital for tackling bacterial infections which cause pneumonia, meningitis and sepsis, and protecting against infection during chemotherapy.
Resistance occurs when bacteria no longer respond to treatment, causing serious complications.
The UKHSA said people should only take antibiotics when they are needed, rather than to treat minor illness, because taking them increases the likelihood that harmful bacteria in the body will become resistant.
Efforts have been made to decrease antibiotic prescribing for this reason.
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The UKHSA said prescribing by GPs has dropped in recent years, driven by reductions in antibiotics given for respiratory infections.
The government agency said the number of these types of infections fell last year, but still remain at a higher level than they were six years ago.
With a reduction in social mixing along with enhanced hand hygiene and fewer people in hospital, infections fell from 65,583 in 2019 in England to 55,384 in 2020.
But the proportion of bloodstream infections which are resistant to some antibiotics increased in the same period, meaning a rise in these infections is likely as people mix freely again.
Dr Susan Hopkins, chief medical adviser at the UKHSA, said: "AMR (antimicrobial resistance) has been described as a hidden pandemic and it's important that we do not come out of COVID-19 and enter into another crisis.
"It is likely that COVID-19 restrictions in 2020 including enhanced infection, prevention and control measures also played a part in driving down antibiotic resistance and prescribing.
"While these measures were severe, serious antibiotic-resistant infections will rise once again if we don't act responsibly and that can be as simple as regular and thorough handwashing.
"As we head into winter, with increasing amounts of respiratory infections in circulation, it's important to remember that antibiotics are not needed for many cold-like symptoms.
"Stay at home if you feel unwell.
"Taking antibiotics when you don't need them only puts you and your loved ones at more risk in the future so please listen to your GP, nurse, dentist or pharmacist's advice."