Texas recently put old death certificates online and I was able to look at several for relatives and others who I have researched. I found Pneumonia listed as the cause of death for my wife's great great grandparents who died within days of each other.
William Smith Telford died on February 03, 1934 in Abilene, Texas after coming down with pneumonia and his wife Louisiana English Pennington Telford followed him on February 15, 1934. They were both in their nineties so maybe they were ready to go. This photo was taken on their 60th wedding anniversary in 1925.