Almost half of the hospitals in England declared a major alert in the first week of the year as the health service came under increasing pressure.
Some 66 of 142 trusts issued operational pressure alerts as bed shortages intensified and A&E departments became overwhelmed.
Overall, NHS hospitals issued 226 serious alerts in just six days, saying they were experiencing major pressures.
The data from NHS England, which covered the six days up to last Sunday, shows the number of alerts was more than six times higher than the previous six days.
There were 226 operational pressure alerts at either level 3 or 4 across the six days to January 8 compared with 34 from December 28 to January 2.
Overall, 58 NHS trusts reported that they were at level 3 on at least one day, while a further eight trusts reported level 4 at least once during the week - meaning patient safety was at risk.
Official NHS guidance says that level 3 is when the local health and social care system "is experiencing major pressures compromising patient flow and continues to increase.
"Further urgent actions are now required across the system by all A&E Delivery Board partners, and increased external support may be required."
Level 4, the most serious level, shows that pressure in the local health and social care system "continues to escalate, leaving organisations unable to deliver comprehensive care.
"There is increased potential for patient care and safety to be compromised."