Risk assessment of urban yellow fever virus transmission in Kenya: is Aedes aegypti an efficient vector?

Figures & data

Table 1. Susceptibility of Aedes aegypti mosquitoes from Mombasa, Kisumu, and Nairobi to oral infection with yellow fever virus.

		Percent infected^a (No. infected/No. tested) by days post-exposure to yellow fever virus
Area	State of the virus	7	14	21	Total
Nairobi	Frozen	14 (10/70)	7 (4/56)	11 (4/34)	11 (18/160)
	Freshly cultured	13 (2/15)	20 (3/15)	10 (2/20)	14 (7/50)
	Total	14 (12/85)	9 (7/71)	11 (6/54)	12 (25/210)
Kisumu	Frozen	22 (21/92)	27 (24/87)	28 (24/84)	26 (69/263)
	Freshly cultured	25 (5/20)	45 (9/20)	20 (5/25)	29 (19/65)
	Total	23 (26/112)	30 (33/107)	26 (29/109)	26 (88/328)
Mombasa	Frozen	25 (20/78)	30 (19/63)	14 (10/68)	23 (49/209)
	Freshly cultured	26 (4/15)	40 (6/15)	21 (6/28)	27 (16/58)
	Total	25 (24/93)	32 (25/78)	16 (16/96)	24 (65/267)

^a Infection rate (No. infected/No. tested * 100).

Table 2. Susceptibility of Aedes bromeliae mosquitoes from Mombasa and Nairobi to oral infection with yellow fever virus (YFV).

	Percent infected^a (No. infected/No. tested) by days post-exposure to YFV				Percent disseminated^b (No. disseminated/No. tested) by days post-exposure to YFV
Area	7	14	21	I.R.^c	7	14	21	D.R.^d	D.R.(I)^e
Nairobi	11 (2/18)	12 (3/26)	17 (5/30)	14 (10/74)	0 (0/18)	4 (1/26)	3 (1/30)	3 (2/74)	20 (2/10)
Mombasa	0 (0/14)	21 (4/19)	48 (10/21)	26 (14/54)	0 (0/14)	5 (1/19)	5 (1/21)	4 (2/54)	14 (2/14)
Total	6 (2/32)	16 (7/45)	29 (15/51)	19 (24/128)	0 (0/32)	4 (2/45)	4 (2/51)	3 (4/128)	17 (4/24)

^a Infection rates (No. infected/No. tested * 100).

^b Dissemination rate (No. disseminated/No. tested * 100).

^c Total infection rate (total No. infected/total No. tested * 100).

^d Total dissemination rate (total No. disseminated/total No. tested * 100).

^e Total dissemination rate for infected mosquitoes (total No. disseminated/total No. infected * 100).

Table 3. Susceptibility level of Aedes mosquitoes inoculated intrathoracically with yellow fever virus.

Area	Mosquito species	Percent infected^a (No. positive/No. tested)
		Body	Saliva
Nairobi	Ae. aegypti	100 (12/12)	0 (0/12)
Kisumu	Ae. aegypti	100 (16/16)	0 (0/16)
Mombasa	Ae. aegypti	100 (16/16)	0 (0/16)
Mombasa	Ae. bromeliae	100 (1/1)	100 (1/1)

^a Percent infected (No. positive/No. tested * 100).

Figure 1. Maximum likelihood tree inferred using the (T92 + G + I) model of sequence evolution for COI barcode region (860 bp) of yellow fever midgut infected (SS) and non-infected (NS) Ae. aegypti samples from Nairobi (NRB), Kisumu (KSM), and Mombasa (MSA), Kenya. The number of individuals sharing a haplotype is indicated in parentheses. Bootstrap support values from 1000 replications ≥65 and Bayesian posterior probabilities ≥90 are indicated above and below the three major lineages, respectively, with terminal nodes reflecting bootstrap support values alone. Aedes ochraceus was included as an outgroup.