On September 20, Hurricane Maria struck the Caribbean, devastating Puerto Rico and the U.S. Virgin Islands. Almost two weeks later, the islands are mired in a severe humanitarian crisis that shows no signs of abating anytime soon. Here is what you should know about the islands and their current situation:

Where are Puerto Rico and the U.S. Virgin Islands?

Puerto Rico is a Caribbean island located due east of Haiti and the Dominican Republic. Miami, Florida, is about 1,035 miles from the island’s capital city of  San Juan. The island is approximately 3,500 square miles and has a population of about 3.4 million.

The U.S. Virgin Islands are a group of islands located 40 miles east of Puerto Rico and due south of the British Virgin Islands. The 134-mile territory includes the main islands of Saint Croix, Saint John, and Saint Thomas, as well as many other surrounding minor islands. The U.S. Virgin Islands (USVI) has a population of a little more than 100,000.

How are Puerto Rico and the U.S. Virgin Islands connected to the United States?

During the Spanish-American War in the late 1890s the U.S. military invaded the Spanish-owned island of Puerto Rico. After the war ended, the United States retained control, making the islands an unincorporated territory. Residents of Puerto Rico have been natural-born U.S. citizens since 1917.

That same year the U.S. government paid Denmark $25 million to purchase the territory now officially known the Virgin Islands of the United States. U.S. citizenship was granted to the residents of the islands in 1927.

Why is the devastation in the area so severe?

When Hurricane Maria struck the areas of Puerto Rico and the U.S. Virgin Islands it became the fifth-strongest hurricane to ever hit the United States. Jeff Weber, a meteorologist with the National Center for Atmospheric Research, said Hurricane Maria “was as if a 50- to 60-mile-wide tornado raged across Puerto Rico, like a buzz saw,” adding, “It's almost as strong as a hurricane can get in a direct hit.”

How many deaths have been attributed to the storm?

The office of the governor of Puerto Rico reports that 16 people died so far because of Hurricane Maria. However, many more deaths than have been officially listed may be due to the storm. As the Miami Herald reports, “The dead are at the hospital morgues, which are at capacity and in remote places where the government has yet to go. In many cases, families are unaware of the deaths. The government’s Demographic Registry is responsible for certifying deaths so bodies can be removed by funeral homes, many of which are not operating because of lack of resources.”

How many people has the U.S. government sent in response to the crisis?

According to FEMA there are more than 10,000 federal staff representing 36 departments and agencies, including more than 800 FEMA personnel on the ground in Puerto Rico and the U.S. Virgin Islands engaged in response and recovery operations.

What is the current situation in Puerto Rico and USVI?

The following information, which was current as of Sunday, October 1, is based on data provided by the Federal Emergency Management Agency (FEMA):

• Federal search and rescue crews saved or assisted a total of 843 individuals in Puerto Rico and USVI.

• In Puerto Rico there are currently 10,056 people living in shelters, while in USVI about 555 are occupying shelters.

• In Puerto Rico 60 of 69 hospitals are fully operational, though only 9 have power restored. The hospital ship USNS Comfort has left from its base in Norfolk, Virginia, and is expected to arrive mid-week. A fuel rotation plan has also been put in place to ensure hospitals have continuous power. (Last week Reuters reported that fuel had become so precious that deliveries to hospitals were being made by armed guards to prevent looting.)

• Less than half of the population of Puerto Rico (45 percent) has access to water that is clean enough to drink. Currently, only 9 of 52 of the island’s aqueduct and sewer-authority wastewater treatment plants are operational (19 are non-operational, and the EPA is continuing to assess the remaining 24).

• On Puerto Rico, 49 percent of grocery/big box stores have reopened.

• Only 11.3 percent of Puerto Rico has mobile phone service. Public Safety Answer Points/911 centers are operational, but many continue to have generator/fuel issues. On USVI, only 30.2 percent of the cell towers are operation.

• About half of the population of Puerto Rico (1.6 million citizens) is without power. (Because 20 percent of overhead transmission lines need replacement, it may take several years to completely rebuild the infrastructure.) On USVI, the power plants on St. Thomas and St. Croix have returned to normal and are providing power to critical facilities.