(Bloomberg) -- The worldwide Covid-19 crisis shows that infectious diseases present a “perpetual challenge,” and officials have to be better prepared for them, outgoing presidential adviser Anthony Fauci said in an opinion piece.

While a rich and varied supply of treatments once lulled doctors into believing that infectious diseases no longer presented a threat, outbreaks from HIV to Covid-19 have reversed that thinking, Fauci said in the essay published in the New England Journal of Medicine. 

“It’s never over because we will continually be beset with new, emerging and reemerging infectious diseases similar to what we’re experiencing right now with Covid,” he said in an interview.

Fauci will step down as President Joe Biden’s chief medical adviser and director of the US National Institute for Allergy and Infectious Diseases at the end of the year. Covid is just the latest outbreak Fauci has responded to in his 54 years at the National Institutes of Health: Others include SARS, West Nile virus, swine flu, infectious hepatitis, Zika virus and Ebola virus. He’s said that one of his greatest disappointments as head of NIAID was the failure to devise an effective vaccine against HIV, which continues to kill some half a million people worldwide annually. 

Society tends to give less attention to unknown or rare threats, no matter how severe they may be, which is why the world hasn’t been well prepared for pandemics, Fauci said. 

“I guess it’s human nature that you focus on what the immediate threat that you can see as opposed to the threat that might occur that you don’t see yet,” he said in the interview. 

Fauci said he would advise his eventual successor to follow the science and stay away from the politics. 

“We’re living in a very unusual situation that’s somewhat slanted toward anti-science and a lot of politicization,” he said.

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