Iranian prison authorities have allowed jailed Washington Post reporter Jason Rezaian to get outside medical treatment and receive some care packages in recent weeks amid a groundswell of signatures on an online petition urging his release.

Ali Rezaian, the imprisoned reporter’s brother, said Thursday in an interview that his sibling briefly left prison twice recently to see specialists who prescribed antibiotics for infections in his eye and groin area.

“He’s feeling better,” said Ali Rezaian, who noted that the infections went untreated for more than a month. “But as a result of the delayed treatment, it’s harder for him to recover.”

The 38-year-old Jason Rezaian, The Post’s bureau chief in Iran, has been held in Tehran’s Evin Prison since security forces raided his home in July and arrested him and his wife, journalist Yeganeh Salehi. She was eventually released on bail. Their case has been referred to a Revolutionary Court jurist known for imposing long and severe sentences.

A dual national who holds American and Iranian citizenship, Rezaian has been detained longer in Iran than any journalist before him. The charges against him are cloaked in secrecy, with little public information beyond a statement by authorities that he is accused of acting beyond the scope of journalism. He has not been permitted to consult a lawyer.

But there are signs that the prison authorities have eased at least some of the harsh conditions. He was recently released from solitary confinement and placed in a cell with another prisoner.

He also has been allowed several visits from his wife, who brought him books, food and warm clothes fitting for the cold Tehran winter, Ali Rezaian said. He has read the books she brought him in January twice already, the brother said.

State Department negotiators engaged in talks with Iran over its nuclear program have repeatedly asked for the release of Jason Rezaian and two other Americans also imprisoned there, plus information on another American long missing in the country. Mohammad Javad Zarif, Iran’s chief negotiator, has said he was instrumental in arranging two visits to Rezaian late last year by his mother and mother-in-law.

It is uncertain whether U.S. officials will have many opportunities to press Rezaian’s case after late March, when they have said they must reach an agreement with Iran on major principles or there is no point in continuing the nuclear talks up to a June 30 deadline.

Meanwhile, a burgeoning online petition drive has collected signatures from people in more than 70 countries asking Iran to immediately set Rezaian free. The petition on Change.org has collected more than 100,000 signatures, a dramatic rise from less than 10,000 just a few weeks ago.

Ali Rezaian said he quietly posted the petition around the Thanksgiving holidays. But in mid-January, Change.org began aggressively pushing it through e-mail and its social-media accounts on Twitter and Facebook, said the Web site’s spokeswoman, Shareeza Bhola.

“Online petitions show that a situation is not isolated,” Bhola said. “It amplifies voices calling for justice. It’s not just a few people calling for Jason’s freedom — it’s 100,000.”

Ali Rezaian said he would love to see the petition get a million or more signatures, a goal he said he considers achievable. Then he paused and corrected himself.

“I’d love to see Jason get out tomorrow,” he said. “I’d rather be able to take the petition down. No number is big enough.”