Why chikungunya disease in Mombasa could spread to Nairobi, Kisumu

By Gatonye Gathura

The viral disease, chikungunya, that has hit Mombasa with about 1,200 suspected cases could spread to Nairobi and Kisumu, warn medical experts.

The experts have confirmed the mosquito responsible for the Mombasa outbreak is also abundant in Nairobi and Kisumu.

They have also confirmed that similar mosquitoes residing in Kisumu and Nairobi have the capacity to transmit the disease and that conditions in all these towns are excellent for the insects to thrive.

All that is required now, a team of local and foreign experts warn is an infected person from Mombasa to travel to Kisumu or Nairobi and an outbreak could be triggered.

“The most likely way that chikungunya (CHIKV) may be introduced into new areas is the travelling of an infected person to areas where a competent mosquito vectors exists,”

The second possible way the disease could spread is for an infected mosquito to be transported from Mombasa to the other towns.

The female Aedes mosquito, the experts say loves a human meal, lives outdoors, feeds in the afternoon, is a city dweller and breeds in uncollected garbage and less disturbed domestic water containers.

Recently researchers at Kenya Medical Research Institute (KEMRI) and the International Centre of Insect Physiology and Ecology, had investigated whether mosquitoes in Mombasa, Nairobi and Kisumu could transmit the disease.

Their findings published last month, say mosquitoes in the three towns are competent to transmit the disease and warned health authorities to step up surveillance in all the cities.

In August the Vector Borne Disease Control Unit of the, Ministry of Health, KEMRI and Stanford University, US, had warned of possible escalation of chikingunya in urban centers.

The teams had compared the lifestyles of rural and urban chikingunya mosquito at the coast region and western Kenya.

The study in Kisumu town and Chilambo areas in western Kenya and Ukunda and Msambweni at the coast confirmed this mosquito to be largely an urban dweller.

The mosquito, the researchers says are being attracted to urban areas, by the high human populations living under mounds of garbage and dirty environments. Due to poor water supply the towns most residents keep many water containers around the household.

Such conditions, the research say offer best breeding grounds for the mosquito whose females have developed an appetite for human meal over other animals.

Unlike the malaria mosquito, which largely feeds indoors and at night the Aedes, the scientists explain largely live outdoors and feed during daytime making it impossible to control with bed nets.

Their afternoon feeding habits, the scientists say may coincide with periods of most human communal activities and an ideal opportunity for disease transmission, especially in schools.

“It is important to note that currently there are no control methods against this mosquito either by national or county governments in Kenya,” says the study.

However the researchers say the most effective control method to keep this mosquito away is to maintain a clean environment.

The word chikungunya comes from the Makonde of Tanzania where the disease was first detected in 1952 and means ‘bent over in pain.’

While deaths are rare from the disease, it can cause chronic joint pains that in some people can last for years.


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