It's absolutely completely and directly caused by the U.S. blockade against Cuba. The UN has reported this.
They just came out last week with a report. They've warned that the expansion of the sanctions imposed on Cuba is causing widespread harm to the population and endangering lives, and they must be lifted immediately.
Businesses are over-complying due to the risks and threats from the United States. Every sector—energy, finance and shipping—is being affected by this now.
When you also factor in Cuba's total isolation from international payment systems, Cuba is at risk of widespread suffering and disease in the very near future. This is because of the U.S. blockade.