MegaCLI Media Error Count

This morning, I just got a Nagios alarm because of:

BRUBLUst01:/usr/local/bin# /opt/MegaRAID/MegaCli/MegaCli64 -PDList -a0

Adapter #0

Enclosure Device ID: 32
Slot Number: 0
Device Id: 0
Sequence Number: 2
Media Error Count: 1
Other Error Count: 0
Predictive Failure Count: 0
Last Predictive Failure Event Seq Number: 0
Raw Size: 715404MB [0x575466f0 Sectors]
Non Coerced Size: 714892MB [0x574466f0 Sectors]
Coerced Size: 714880MB [0x57440000 Sectors]
Firmware state: Online
SAS Address(0): 0x1221000000000000
Connected Port Number: 0(path0)
Inquiry Data: ATA ST3750640NS 3BKS 5QD3ZT7W

I found the meaning of other error count but not media error count, doesn't looks like MegaCLI is really well documented. What does this means? A broken sector on a disk? Should I care?

Thanks for your help,