Scammers have found ample opportunities during the coronavirus pandemic to capitalize on widespread fear and desperation as roughly 100,000 people across the country have fallen ill and more than 1,300 have died.

Authorities across the state of California have reported confiscating fake testing kits, investigating price-gouging vendors, and fielding reports of fraudsters claiming to be from the Centers for Disease Control and Prevention, or the World Health Organization. Experts say the elderly, who face the highest risk of dying from COVID-19, are often the targets of these crimes, which can range from false promises about nonexistent cures to rackets like the “family scam.”

Karen, a woman in her 70s who was recently moved from her home outside of Pleasanton, said she fell victim to this trap earlier this month when she received an urgent call supposedly from her adult nephew, Christopher.

Panicked and speaking in a wild stream of consciousness, he explained that he’d been infected with coronavirus and thought he was answering a call from his doctor when he’d caused a car accident. Two people were injured and now he was in jail. Someone who claimed to be Christopher’s attorney would later give Karen instructions and arrange for a courier — he needed $13,000 in cash for bail.

Karen, whose real name is being withheld in accordance with The Chronicle’s policy on anonymous sources, said she rushed to the bank. She split $100 bills into four separate stacks, placed them in an envelope and waited for the courier to arrive. After the handoff, she tried to call Christopher’s attorney, but the number was out of service. A devastating reality began to set in for Karen.

“By then I was sure that I had been scammed,” she told The Chronicle.

Victims’ bank accounts have been drained in such fashion for decades. Other cons reported in recent weeks use similar playbooks, with details refashioned to fit the current crisis. But authorities say the COVID-19 outbreak has created a unique opportunity for scammers, and, as a result, efforts are being made to alert the public.

Detectives with the Alameda County Sheriff’s Office are investigating Karen’s case, and inspectors from across the region are following up on stores accused of price-gouging on vital goods like food and hand sanitizer. California officials announced the first federal prosecution tied to the pandemic this week.

The FBI arrested a Southern California man on Wednesday for soliciting investments in a company hawking concoctions he said could prevent and cure COVID-19. Keith Lawrence Middlebrook, a 53-year-old actor and owner of a sports entertainment company, allegedly claimed to have invented a “patent-pending cure” and a treatment that prevents infection. Health officials across the globe have said there is no known vaccine or antiviral treatment at this time.

While most of Middlebrook’s social media accounts have been suspended, a March 13 YouTube video shows him downplaying the seriousness of the disease and apparently touting a cure.

“There’s already an antidote,” he said. “People are getting up out of the hospital and walking away.”

Middlebook texted a cooperating witness in the investigation and said that he had developed a cure for a COVID-19 patient in Los Angeles who tested positive but “got up and walked out 51 hours after my Injection,” according to the affidavit.

He allegedly tried to recruit backers by saying a “conservative” return on their investment would be worth $200 million to $300 million.

Middlebook was arrested after he allegedly delivered pills to undercover agents posing as an investor.

“During these difficult days, scams like this are using blatant lies to prey upon our fears and weaknesses,” said U.S. Attorney Nick Hanna, whose Central District of California office is prosecuting the case. “While this may be the first federal criminal case in the nation stemming from the pandemic, it certainly will not be the last.”

Daly City police reported a similar scam, where someone claiming to be from the CDC offered to let people “reserve a vaccine for the COVID-19” with a credit card and/or social security number.

“There is no vaccine reserve program, and the CDC is not offering anything of the sort,” agency officials said on Twitter. “Do not fall prey!”

New scam: People are claiming to be from the CDC offering to let people "reserve a vaccine for the COVID-19" with a credit card and/or social security number. There is no vaccine reserve program, and the CDC is not offering anything of the sort. Do not fall prey! — Daly City Police (@DalyCityPD) March 17, 2020

Scammers have historically zeroed in on older victims, and experts say the latest schemes are no different.

“Seniors are the targets, there’s no doubt about that,” said Sgt. Ray Kelly, a spokesman for the Alameda County Sheriff’s Office. In the so-called “family scams,” he said, fraudsters may do research to learn the name of an actual family member or even pretend to be a real person who’s easily searchable online.

All of this was true for Karen. The man who called knew her nephew’s name, and a second impersonator claimed to be an Alameda County public defender, according to her online search.

Karen hadn’t spoken to Christopher in years, and wouldn’t have recognized his voice, but details of the story made it seem real, she said. The “attorney” said things that made him sound official, like his precise instructions for a letter to the bail bonds company and how to interact with the courier.

The scammer claimed that Karen’s nephew had answered the phone while he was driving, believing it could be his doctor, but that that detail would put “Christopher” at risk of an expensive lawsuit. The man pretending to be an attorney said he would draw up a non-disclosure agreement and that it was imperative Karen not discuss it with police, jailers or people at the bank.

“He said we don’t want anybody to get wind of the fact that Christopher was on the phone; the victims do not know that,” she said. “So that made sense to me that nobody should hear.”

He also told Karen not to call Christopher’s parents.

“Every family has their own issues,” she recalled him saying.

After reporting the incident to police, Karen called her in-laws, the parents of the real Christopher. They were gracious and sorry for what happened, she said, and thanked her for trying to support their son.

“I have beaten myself up about this,” Karen said, adding that the best advice she has for other potential victims is to stop and think before reacting.

“Pay attention to anything that doesn’t square with what you know to be logical or credible or true,” she said. “I’ve never really had experience with somebody just totally lying to my face.”

Megan Cassidy is a San Francisco Chronicle staff writer. Email: megan.cassidy@sfchronicle.com Twitter: @meganrcassidy