Cyclone Chido has become the worst storm in 90 years to hit the French overseas territory of Mayotte in the Indian Ocean.

Here’s more on the destruction caused by Chido and what could happen next:

What is Cyclone Chido?

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

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

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

The terminology can be a bit confusing. Tropical cyclones are called hurricanes when they occur in the Atlantic Ocean, the Gulf of Mexico, the Caribbean, and the northeastern Pacific, and are called typhoons when they occur in the western Pacific. And when they occur in the South Pacific and Indian Oceans, they are called cyclones.

Chido developed into a cyclone and hit Mayotte, an archipelago of 320,000 people off the east coast of Africa. While Mayotte is located in the Indian Ocean, it is an overseas department of France and is governed directly from Paris. However, it is the poorest region in France and an estimated one third of the population lives in slums.

The cyclone also hit surrounding countries in southeastern Africa, bringing heavy rains and damaging homes in Madagascar, Mozambique and the Comoros before weakening.

An initial estimate suggests at least three people have died in Mozambique, local officials told AFP.

When and where did Chido end up?

Chido hit Mayotte on Saturday morning with winds exceeding 220 km/h (137 mph).

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

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

According to the National Hurricane Center in the United States, Category 4 storms with winds 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 tear down utility poles, which can lead to power outages.

How many people were killed by Chido in Mayotte?

According to the French Interministerial Crisis Management Operations Center (COGIC), the official death toll in Mayotte from Chido is 19 people.

However, there are fears that Chido actually killed hundreds of people.

The French Interior Ministry said “it will be difficult to count all the victims” and a final number of those affected by Chido has not yet been determined.

Determining the death toll could take “days and days,” Interior Minister Bruno Retailleau told French media. Retailleau arrived in Mamoudzou, the capital of Mayotte, on Monday.

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

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

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

The insecurity is partly due to the large number of undocumented migrants in Mayotte – over 100,000, according to French authorities. In addition, a French Interior Ministry official said determining the death toll was complicated because “Mayotte is a Muslim country where the dead are buried within 24 hours.”

Many of Mayotte’s migrants come from neighboring Comoros and East African countries such as Somalia. They are attracted by the greater economic opportunities that Mayotte’s status as a French department brings.

How badly damaged is Mayotte’s infrastructure?

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

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

“The health system is seriously compromised and access to health care has been significantly affected,” outgoing French Health Minister Genevieve Darrieussecq said on Sunday.

The control tower at Mayotte’s main airport, Dzaoudzi-Pamandzi, was also damaged. This has made rescue operations more difficult as only military aircraft can fly to Mayotte.

Mayotte has been almost entirely offline for more than 36 hours, according to internet monitoring group NetBlocks. COGIC reported that 15,000 people experienced power outages.

Impoverished communities were hit hardest by the cyclone. The slums of Mayotte, where most houses are built of tin, 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 considered the poorest territory in the European Union. Three out of four people in the island nation live below the poverty line.

Mayotte has been struggling with water shortages, drought and a lack of investment for years.

Where is Chido now?

By 0900 GMT on Monday, Chido had weakened to a remnant low or post-tropical cyclone just south of Balaka township in Malawi. The speed was 45 km/h (28 mph).

What’s next?

Chido is expected to dissipate near Zimbabwe on Tuesday, according to ReliefWeb.

Cyclones typically form in the southwest Indian Ocean from November to April. On average, 12 hurricanes form every year.

In 2019, Cyclone Idai killed more than 1,300 people in countries including Malawi, Mozambique and Zimbabwe. In 2023, Cyclone Freddy caused a month of storms that 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 hurricanes are becoming more intense due to climate change and warming waters.

“The Indian Ocean is warming rapidly and will 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 cyclones need to be better monitored to prevent destruction like that caused by a cyclone like Chido. He added that governments need to fund agencies that monitor the storms. According to the European Organization for the Use of Meteorological Satellites, better monitoring can lead to timely warnings for residents of areas where impacts from a cyclone are predicted.

In addition, Koll said, countries must “disaster-proof” coastal cities and ensure infrastructure is prepared to minimize hurricane damage and save lives and livelihoods. Coastal cities in particular are vulnerable to storm surges and flooding.