Saudi Arabia says 282 people are now confirmed to have been killed by the Mers virus, almost 100 more than initially thought.
The increase came after a national review of hospital data from the time the virus emerged in 2012.
The deputy health minister, who has been criticised for his handling of the crisis, was sacked on Monday.
Cases of the virus, for which there is no known cure, have been confirmed in almost a dozen other countries.
Saudi authorities said there had now been 688 confirmed Mers (Middle East Respiratory Syndrome) infections in the kingdom. Before the revision the number of cases was believed to be 575.
Saudi health ministry spokesman Tariq Madani said that despite the revised figures, fewer people were now contracting the disease.
"Though the review showed confirmed cases that needed to be added, we are still witnessing a decline in the number of newly registered cases in the past few weeks" he said.
Of those infected, the country's health ministry said, 53 were still receiving treatment.
Saudi Arabia has registered the largest number of infections of Mers.
The virus is from the same family as the common cold, but can lead to kidney failure and pneumonia.
What is Mers?
- Acronym for Middle East Respiratory Syndrome
- A type of coronavirus which causes respiratory infections
- First death recorded in 2012 in Saudi Arabia
- Camels are suspected to be the primary source of infection for humans
Cases have also been confirmed in Jordan, Qatar, the United Arab Emirates, France, Germany, Italy, Tunisia, Egypt, the UK and, most recently, the US.
Camels are suspected to be the main source of infection for humans. Saudi authorities have urged citizens to wear protective masks when dealing with the animals.
The government's handling of the outbreak has been criticised, says the BBC's Arab affairs editor Sebastian Usher.
Critics have accused it of rejecting outside scientific help that might have helped stem the spread of the virus, our correspondent says.
The ministry of health says it's working with the World Health Organization (WHO) and the US based Centre for Disease Control and Prevention to deal with the crisis.
On Monday, the day before the figures were revised, the Deputy Health Minister Ziad Memish was sacked without explanation.
In April Saudi's King Abdullah sacked the health minister as the death toll climbed.