Saturday 23 March 2019

Thousands feared to have died after Cyclone Idai sweeps across Southern Africa.

A total of 675 people have now been confirmed dead after Cyclone Idai swept across Southern Africa last week, and it is feared that many more will be found to have died as floodwaters recede. The storm made landfall near the city of Beira in Mozambique on Friday 15 March 2019, bringing with it high winds and flooding that have displaced about 2.6 million people across Southern Africa, and causing hundreds of fatalities, with 359 deaths recorded in Mozambique so far, with 259 fatalities recorded in Zimbabwe, 56 in Malawi and one in Madagascar.

Flooding in Sofala Province, Mozambique, on Wednesday 20 March 2019 following the passage of Cyclone Idai. Adrien Barbier/AFP/Getty Images.

The storm was one of the largest ever recorded in the Southern Hemisphere, and has caused immense damage to infrastructure and loss of life across some of the poorest nations in the region, with aid agencies in the region particularly concerned about the long term effects of the storm, which has destroyed crops, crippled transport networks and contaminated water supplies. Hundreds of thousands of people in the region are now living in overcrowded makeshift camps where disease could potentially spread very quickly, with the International Federation of Red Cross and Red Crescent Societies already reporting cases of Cholera in Mozambique and a rise in Malaria cases across the region.

Victims of flooding trapped on the rooves of buildings in Mozambique. Instituto Nacional de Gestão de Calamidades.

Tropical storms (referred to as Cyclones in the Indian Ocean) are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. If this happens over a large enough area the inrushing air will start to circulate, as the rotation of the Earth causes the winds closer to the equator to move eastwards compared to those further away (the Coriolis Effect). This leads to tropical storms rotating clockwise in the southern hemisphere and anticlockwise in the northern hemisphere.These storms tend to grow in strength as they move across the ocean and lose it as they pass over land (this is not completely true: many tropical storms peter out without reaching land due to wider atmospheric patterns), since the land tends to absorb solar energy while the sea reflects it.

Flooding in Mozambique this week. Lutheran Media Forum.

Despite the obvious danger of winds of this speed, which can physically blow people, and other large objects, away as well as damaging buildings and uprooting trees, the real danger from these storms comes from the flooding they bring. Each drop millibar drop in air-pressure leads to an approximate one centimetre rise in sea level, with big tropical storms capable of causing a storm surge of several meters. This is always accompanied by heavy rainfall, since warm air over the ocean leads to evaporation of sea water, which is then carried with the storm. These combined often lead to catastrophic flooding in areas hit by tropical storms.

A bridge destroyed by floodwaters associated with Cyclone Idia Chimanimani District in eastern Zimbabwe. AFP/Getty Images.

Cholera is caused by the waterborn Bacterium Vibrio cholerae, a Gram-negative, comma-shaped Gammaproteobacteria, related to other pathogenic Bacteria such as Yersinia pestis (Bubonic Plague), and Esherchia coli (food poisoning). The Bacteria produce proteins which can cause watery diarrhoea, which helps spread the disease, and can prove fatal in severe cases, as patients are killed by extreme dehydration, and the disease can spread rapidly when disasters such as floods cause normal sanitation practises to break down. Malaria is caused by the parasitic Protist Plasmodium, a single-celled eukaryotic organism spread by Mosquitoes, insects which live in water during the larval stages of their life cycle. Flooding events can lead to explosions in Mosquito populations, as more nurseries become available for their young, as well as herding people together into much closer proximity, where it is easier for Mosquito-carried (and other) diseases to spread.

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