Due to Rav Elyashiv's failed health and deteriorating situation, Rav Chaim Kanievsky has requested, according to statements published in the 3 daily Haredi newspapers, that people accept upon themselves to fast tomorrow, Thursday - the last day of the special "Shovavim period", for the health of Rav Elyashiv.
Rav Kanievsky said that the best is for people to accept a full-day fast, but those who cannot should at least fast for half a day. As well, only someone who's regular learning schedule will not be affected should fast. One who will not be able to maintain his regular learning, should not fast.