Islamabad: Overcrowded hospitals in Pakistan’s biggest city, Karachi, have started turning new arrivals away as the Delta variant of Covid-19 sweeps the 20-million-strong metropolis, officials and medics said on Wednesday. The government in the southern province of Sindh described the situation as alarming, as a quarter of all coronavirus tests came back positive on Tuesday. "It is a very serious situation,” said Mutaza Wahab, a spokesperson for the Sindh government. The Delta variant, which was first identified in neighbouring India where it brought the healthcare system to its knees, now accounts for more than 90 percent of new infections in Karachi, Wahab added. Pakistan is bracing itself for the fourth wave of the coronavirus and health authorities fear it may turn out to be the worst one yet due to the high transmission rate of the Delta variant. (dpa)