In today's news (18 March 2020), the Sephardic Chief Rabbi of Israel ruled that Jews may use their cellphones on Shabbat to receive developments and alerts regarding the coronavirus.
This is an invocation of pikuach nefesh to enable people to receive news that might save their own lives' or others'.
Does the invocation of pikuach nefesh to break Shabbat have to come from a rabbi (if there is time to consult one), or can it be a personal decision? What is the halacha?