Please do not consider this comment to be commentary on the ongoing coronavirus outbreak, especially considering the situation at the nursing home in Washington state.

Out of curiosity, I tried to find examples where many people died of a flu outbreak in nursing homes. Here are some articles I found:

This article describes a nursing home in Sheffield where 9 of 60 residents died from the flu during the 1997--1998 season: https://pdfs.semanticscholar.org/e54b/27d527dd0612d0899f22ea...

This article describes a nursing home in Honolulu where 6 of 37 residents died from the flu during the 1989--1990 season: https://www.ncbi.nlm.nih.gov/pubmed/7657975

This article describes a nursing home in Los Angeles where 8 of 101 residents died from RSV in 1979: https://www.ncbi.nlm.nih.gov/pubmed/6527041

This article describes a nursing home in Devon where 4 of 50 residents died from RSV within one week: https://www.ncbi.nlm.nih.gov/pubmed/6736667