OK, since I cannot answer so many phone calls, whatsapp messages and emails, here's a post about my father's condition: he had been growing steadily weaker over the last couple of months, until he lost the use of his right hand, then he fell down in the bathroom at dawn on the Bengali New Year's day (Saturday April 15), and had to be bodily lifted and hospitalized. A CT scan followed by an MRI revealed a suspicious looking growth in the brain, but the neurosurgeon said he strongly suspected lung cancer which had metastasized to various organs. He has been transferred to a major facility in Kolkata where the oncologist - a dear old boy and close to the whole family - has just begun radiotherapy, not wishing to wait for the biopsy report. He is nearly 79, so wish him luck, if not for a quick recovery then at least a relatively quiet and painless passage. I wouldn't ask for more for myself.
I shall post updates here from time to time.