That's my take on it. The most successful bugs, obviously, are those that kill a very small percentage and then can remain in general circulation until the next mutation -- like our present flu.
The thought that there might be a moderately successful bug that kills 10% is frightening -- but let's be perfectly frank here. That still gives everyone tremendous odds for survival. I'll take a 90/10 any day of the week.
Nonetheless, a literal decimation of the global population would put us in a 10-15 year depression that would make the 1929 crash look like party-time.
A 1929 level economic crash today might lead to TEOTWAWKI. Our society today is not the 1929 society. Two weeks without electrical power in our main cities and they will resemble Mogadishu on a bad day. One week after the ATMs, gas stations and supermarkets are stripped bare, all bets are off. The 50% of police who stay on duty will be pulled in to protect key downtown buildings and VIPs. It will take the "predator class" another few days to realize that police are no longer answering 911 calls for home invasions. (Especially if the phones don't work!)