WASHINGTON (REUTERS) - US Senator Tim Kaine announced on Thursday (May 28) that he and his wife Anne have tested positive for coronavirus antibodies, but that doctors were not able to diagnose the disease early on due to a shortage of Covid-19 tests.

"We each tested positive for coronavirus antibodies this month," the Virginia Democrat said in a statement.

A positive antibody test indicates that they had been previously infected with the coronavirus.

Kaine, a former state governor who was the 2016 Democratic vice-presidential nominee, said he was treated for flu through mid-March but suffered new symptoms late in the month.

His wife experienced "a short bout of fever and chills, followed by congestion and eventually a cough," he said.

"We each talked to our health providers in early April and they thought it possible that we had mild cases of coronavirus," he said.

"Due to the national testing shortage, we were not tested for the virus but continued isolating and watched for any worsening of symptoms. By mid-April we were symptom free," Kaine said.

While noting that coronavirus antibodies could make him less likely to be reinfected or to infect others, Kaine said the actual level of protection is uncertain.

"So we will keep following (US Centres for Disease Control and Prevention) guidelines - hand-washing, mask wearing, social distancing.

"We encourage others to do so as well. It shows those around you that you care about them," he said.