Dödligt virus från Kina orsakar panik (SARS-CoV-2, COVID-19)

Hopes are dimming that "herd immunity" can help stamp out the tenacious global pandemic amid growing concerns that people can be reinfected with COVID-19.

Experts agree that claims of recurring infections require more study since we are only months into the health crisis and evidence has been anecdotal. But if it's proven that recovered patients can "catch" the virus a second time, it would affect their own immunity while also complicating efforts to obtain the Holy Grail of current medical research: effective vaccines.

Recovery from the disease provides antibodies to fight off the infection. The shelf life of those antibodies, however, may be insufficient to protect a patient for very long or promote long-term immunity across populations.

"The possibility of reinfection is certainly real," Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City, told USA TODAY. "And one that I am seeing repeatedly on the front lines."

Glatter says he has cared for a "number of patients" who suffer only mild initial infections, get better and actually test negative for the virus before experiencing a recurrence of symptoms. The intensity can be worse the second time, he says.

"These patients develop difficulty breathing, leading to hypoxia, aches, chest pain, with recurrent and unrelenting fevers and chills," he said, adding that they then test positive again.

Experts caution that it's been only a few months since the first surge of cases in China and around the world. The frequency and severity of reinfections won't be known until cases rise in the areas where there were a significant number of infections last winter, said Dr. Daniel Griffin, chief of infectious diseases at ProHEALTH Care in New York.

"We are months away from knowing for certain if reinfections are possible or a significant issue," Griffin told USA TODAY.