The healthcare workers from two hospitals were involved in treating an Emirati man, 82, who this month became the first in the UAE to contract the virus.
The Health Authority Abu Dhabi said the four, all in stable conditions, had been isolated.
The World Health Organisation said that of the four, a man, 28, and a woman, 30, did not have symptoms. The others, women aged 30 and 40, had mild respiratory problems. All are stable.
The WHO also yesterday confirmed two new cases in Saudi Arabia, one of which was a healthcare worker. It urged hospitals to take the issue more seriously.
Mers has now infected 88 people globally and killed 45.
Among the dead are an Emirati man who died in hospital in Germany in March.
A Frenchman who had been visiting Dubai died in May.
Yesterday, Dr Mansour Al Zarouni, a member of the infection control committee at the Ministry of Health, said the infections “shouldn’t have happened”
“It means either the virus is more easily transferable than we thought, or there was a gross breakdown in infection control practice. Most probably it’s both,” Dr Al Zarouni said.
He said part of the problem was in early diagnosis when a patient comes to the hospital complaining of respiratory problems.
“It is such a common scenario, and you cannot assume the worst for everyone,” Dr Al Zarouni said. “It is kind of impractical.
“However, if you can quickly diagnose the patient to rule in or rule out the virus, then early precautions can be implemented.”
The authority discovered the four new infections after screening 136 people who had been in close contact with the man.
“Healthcare facilities that provide care for patients suspected or confirmed with Mers-CoV infection should take appropriate measures to decrease the risk of transmission of the virus to other patients, healthcare workers and visitors,” WHO said.