There are major fears for the spread of disease as Tonga struggles to pick up the pieces following Cyclone Gita.
The storm hurled its force at the island nation on Monday night, leaving two people reported dead and some islands still completely cut off.
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Newshub reporter Mitch McCann is in Tonga and told The AM Show officials fear water-borne diseases could develop.
Dengue fever is spread by mosquitoes, which breed in warm, damp areas. Much of Tonga has been left flooded and in an unsanitary condition.
Last month an outbreak of the tropical disease broke out across the Pacific, with some victims even reaching New Zealand shores. There is no vaccine available for the tropical disease, which can be fatal, especially in low socio-economic areas.
Four days after Gita hit there are still more than 4000 people crowded into evacuation centres across Tongatapu. McCann told The AM Show the devastation is widespread.
"There are power lines all over the road [in Nuku'alofa]. There are trees everywhere.
"Nuku'alofa itself, the CBD, is sort of a mix between residential and commercial buildings. But every couple of buildings there's one flattened.
"We went to an apartment block and I didn't actually know it was an apartment block until the owner told me because it was on the ground."
No part of the island escaped unscathed, but the southern coast, the eastern coast and the outer islands took the worst hit. Power is still out for most of the main island.
The fate of some of the smaller islands is uncertain. For 'Eua, an island with a 5000-strong population, aid agencies are yet to get through. The NZ Defence Force flew overhead on Wednesday, showing a possible 400 destroyed buildings.
An aid ship will reach the island on Friday morning.
Cyclone Gita is now tracking towards New Zealand.