One week after Hurricane Maria ripped through Puerto Rico, the island faces an alarming shortage of items for basic human needs, such as water and food, and the deficits are threatening a public health crisis.

Nearly half of its 3.4 million residents are without drinking water, and some residents have waited days for a tanker to show up.

Puerto Rico Governor Ricardo Rossello on Monday reported 16 deaths from the Category 4 storm last Wednesday, but that figure is expected to rise.

A water shortage has been exacerbated by the downed power grid. Without electricity, the U.S. territory cannot pump and filter water for tap, and there aren’t enough generators to fill in, or diesel to fuel them.

The island is also facing shortages in drugs, a significant part of its economy. Dozens of drug and medical device companies manufactured pharmaceutical products in Puerto Rico for export globally, so both its people and those outside the territory may not receive “critical lifesaving and life-sustaining drugs,” according to the U.S. Food and Drug Administration.

As of Tuesday, 58 of the island’s 69 hospitals were powerless and lacked fuel, the Federal Emergency Management Agency reported. The U.S. Army on Tuesday delivered a three-day supply of diesel to the San Jorge Children’s Hospital, which had to run its ventilators on batteries for eight hours because it was low on fuel. 

Full power restoration could take four to six months.

By Tuesday, FEMA had provided 6 million liters of water and more than 4 million meals to Puerto Rico and the also-hit U.S. Virgin Islands, and sent 4 million more liters of water and 7 million meals via barge.

The agency says there are three most effective ways the public can help.

The fastest way is by donating money to trusted charitable organizations that can purchase what victims need. Cash can be sent to the Commonwealth of Puerto Rico directly at www.unitedforpuertorico.com, and to the National Voluntary Organizations Active in Disaster at www.nvoad.org.

Donating unsolicited goods could divert volunteer agencies’s resources away from providing services, but those wishing to responsibly donate goods can do so to the National Voluntary Organizations Active in Disaster

People looking to volunteer are encouraged to do so with local and nationally recognized organizations including the Salvation Army and Habitat for Humanity

Public figures have launched their own efforts to assist victims in recent days. Five living former presidents on Monday expanded their One America Appeal donation collection fund to include Puerto Rico and the U.S. Virgin Islands, and Jennifer Lopez and Marc Anthony on Wednesday announced a new alliance to rush food, shelter, medicine, power and communications tools to victims.