The coronavirus has given rise to a flood of conspiracy theories, disinformation and propaganda, eroding public trust and undermining health officials in ways that could elongate and even outlast the pandemic.

Claims that the virus is a foreign bioweapon, a partisan invention or part of a plot to re-engineer the population have replaced a mindless virus with more familiar, comprehensible villains.

Rumors of secret cures — diluted bleach, turning off your electronics, bananas — promise hope of protection from a threat that not even world leaders can escape.

Rumors and patently unbelievable claims are spread by everyday people whose critical faculties have simply been overwhelmed, psychologists say, by feelings of confusion and helplessness.

But many false claims are also being promoted by governments looking to hide their failures,

partisan actors seeking political benefit, run-of-the-mill scammers and, in the United States, a president who has pushed unproven cures and blame-deflecting falsehoods.

The conspiracy theories all carry a common message: The only protection comes from possessing the secret truths that “they” don’t want you to hear.

And it is disrupting the sweeping collective actions, like staying at home or wearing masks, needed to contain a virus that has already killed more than 79,000 people.

A recent study found that people are significantly likelier to share false coronavirus information than they are to believe it.

“We’re seeing scores of people, in a rush to find any comfort, make things worse as they share (sometimes dangerous) misinformation.

In Alabama, Facebook posts falsely claimed that shadowy powers had ordered sick patients to be secretly helicoptered into the state.

In Latin America, equally baseless rumors have proliferated that the virus was engineered to spread H.I.V.

In Iran, pro-government voices portray the disease as a Western plot.

Italian media buzzed over a video posted by an Italian man from Tokyo in which he claimed that the coronavirus was treatable but that Italian officials were “hiding the truth.

Conspiracy theories may also make people feel less alone.

Few things tighten the bonds of “us” like rallying against “them,” especially foreigners and minorities, both frequent scapegoats of coronavirus rumors and much else before now.

A senior Chinese official pushed claims that the virus was introduced to China by members of the United States Army, an accusation that was allowed to flourish on China’s tightly controlled social media.

And outlets that back the Russian government, including branches in Western Europe, have promoted claims that the United States engineered the virus to undermine China’s economy.

And President Jair Bolsonaro of Brazil has repeatedly promoted unproven coronavirus treatments, and implied that the virus is less dangerous than experts say.

It has nourished not just individual conspiracies but a wider sense that official sources and data cannot be trusted, and a growing belief that people must find the truth on their own.

“Medical conspiracy theories have the power to increase distrust in medical authorities, which can impact people’s willingness to protect themselves,” Daniel Jolley and Pia Lamberty, scholars of psychology, wrote in a recent article.

Such claims have been shown to make people less likely to take vaccines or antibiotics, and more likely to seek medical advice from friends and family instead of from doctors.

The wave of coronavirus conspiracies, Dr. Jolley and Dr. Lamberty wrote, “has the potential to be just as dangerous for societies as the outbreak itself.