Cyclone Desire became the worst storm to hit the French overseas territory of Mayotte in the Indian Ocean in 90 years.

Here's more on the destruction caused by Chido and what may come next:

What is Cyclone Chido?

Chido developed from a tropical depression in the southeastern Indian Ocean basin from December 7 to 8.

A tropical depression is an area of ​​low pressure over an ocean associated with circular wind flow produced by thunderstorms. Tropical depressions have maximum sustained wind speeds of 61km/h (38mph) or less.

A tropical depression can intensify and become a tropical storm if wind speeds are from 62km/h (39mph) to 119km/h (74mph). Anything above that is considered a tropical cyclone.

The terminology can be slightly confusing. Tropical cyclones are called hurricanes when they occur in the Atlantic Ocean, Gulf of Mexico, Caribbean Sea, and northeastern Pacific Ocean and are called typhoons when they occur in the western Pacific Ocean. And when they occur in the South Pacific and the Indian Ocean, they are referred to as cyclones.

Chido intensified into a cyclone and hit Mayotte, an archipelago home to 320,000 people on the east coast of Africa. While Mayotte lies in the Indian Ocean, it is an overseas department of France and is governed directly from Paris. However, it is France's poorest region, and an estimated third of the population lives in slums.

The cyclone also affected surrounding nations in southeast Africa, bringing heavy rainfall and damaging homes in Madagascar, Mozambique and the Comoros Islands before weakening.

According to an early estimate, at least three people have died in Mozambique, local officials told the AFP news agency.

When and where did Chido land?

Chido hit Mayotte on Saturday morning with wind speeds of more than 220 km/h (137 mph).

It made landfall in Mozambique on Sunday morning as a tropical storm.

Chido was incredibly powerful. It was equivalent to a Category 4 hurricane at the time of landfall in Mayotte, making it the second strongest type of storm on the Saffir-Simpson scale.

According to the National Hurricane Center in the United States, category 4 storms, which have wind speeds of 209 km/h to 251 km/h (130 mph to 156 mph), cause "catastrophic damage". They can destroy well-built homes, uproot trees and knock down power poles, leading to power outages.

How many people have been killed by Chido in Mayotte?

According to France's Interministerial Crisis Management Operations Center (COGIC), the official death toll in Mayotte as a result of Chido is 19 people.

However, it is feared that Chido actually killed hundreds of people.

The French interior ministry said "it will be difficult to account for all victims" and a conclusive number of those affected by Chido has not yet been established.

Determining the death toll could "take days and days", Interior Minister Bruno Retaileau told French media. Retaileau arrived in Mayotte's capital, Mamoudzou, on Monday.

France sent medical and military personnel on ships and military aircraft to Mayotte.

Rescue workers, including reinforcements from France, are digging through rubble to try to find survivors of the cyclone.

“I think there will definitely be several hundred. Maybe we will reach a thousand, even several thousands," senior local French official Francois-Xavier Bieuville told local media channel Mayotte la 1ere on Sunday.

The uncertainty is partly due to the large number of undocumented migrants in Mayotte – more than 100,000, according to French authorities. Additionally, a French interior ministry official said determining the death toll would be complicated because "Mayotte is a Muslim country where the dead are buried within 24 hours."

Many of Mayotte's migrants come from the neighboring Comoros Islands and East African countries such as Somalia. They are attracted by better economic opportunities that come with Mayotte's status as a department of France.

How badly was Mayotte's infrastructure damaged?

According to COGIC, 830 people were injured, including 24 with serious injuries. In addition, 100,000 people were moved to 70 emergency shelters.

Critical infrastructure in Mayotte was damaged, including roads, water treatment plants and electrical transmission lines.

"The health system is seriously affected, and access to care has been seriously degraded," outgoing French health minister Genevieve Darrieussecq said on Sunday.

The control tower of Mayotte's main airport, Dzaoudzi–Pamandzi, was also damaged. This has made rescue operations difficult because only military aircraft can now fly in Mayotte.

According to internet monitoring group NetBlocks on Monday, Mayotte has been almost completely offline for more than 36 hours. COGIC reported 15,000 people experienced power outages.

Impoverished communities were worst hit by the cyclone. Mayotte's shantytowns, where most houses are built with sheet metal, were not built to withstand the force of a cyclone, and many of the dead are believed to have lived in these areas.

Damage to infrastructure has left some communities in Mayotte without food and water since Saturday, said Salama Ramia, a senator who represents Mayotte in the French Senate.

Mayotte is the poorest French overseas territory and is also believed to be the poorest European Union territory. Three out of four people in the island nation live below the poverty line.

Mayotte has been struggling with water shortages for years, drought and underinvestment.

Where is Chido now?

As of 09:00 GMT on Monday, Chido had weakened to a residual low, or a post-tropical cyclone, slightly south of Balaka township in Malawi. It had a speed of 45km/h (28mph).

What's next?

According to ReliefWeb, Chido is expected to disappear near Zimbabwe on Tuesday.

Cyclones usually form from November to April in the southwestern Indian Ocean. An average of 12 cyclones form per year.

In 2019, Cyclone Idai killed more than 1,300 people in countries including Malawi, Mozambique and Zimbabwe. In 2023, Cyclone Freddy caused storms for a month and killed more than 1,000 people in East Africa. Freddy remained a tropical cyclone for 36 days, and the World Meteorological Organization declared it the longest lasting tropical cyclone on record.

Scientists warn that cyclones are becoming more powerful due to climate change and warm water masses.

"The Indian Ocean is warming at a rapid rate, and it's going to warm much faster in the near future," Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology, told Al Jazeera. He based these findings on research he conducted and published in 2022.

"In fact, the waters where Cyclone Chido developed were 1 to 2 degrees (Celsius - 1.8 to 3.6 degrees Fahrenheit) warmer than usual," Koll said.

Koll said to prevent destruction like that caused by a cyclone like Chido, cyclones need to be better monitored. He added that governments should fund agencies that monitor the storms. Better monitoring could lead to timely warnings for residents living in areas where a cyclone will impact, according to the European Organization for the Exploitation of Meteorological Satellites.

In addition, Koll said, countries must make coastal cities and towns "disaster-proof", ensuring that infrastructure is prepared so that damage from cyclones is minimized and lives and livelihoods are saved. Coastal cities are especially vulnerable to storm surges and flooding.