Optimizing Containment and Control of Candida parapsilosis Fungemia among Neonates in the Outbreak Setting Using a Mathematical Modeling Approach

Table 1

Neonatal candidemia model parameter estimates.

Parameter	Meaning	Standard value (range)	Comments and/or reference
𝑎	NICU admission rate (includes births per day)	0.2 (0.1–0.3); per day	[18]
𝑚	Nondisease causing death rate	0.0001 (0.000001–0.08) per day	4% per year [19, 20]
𝜇	Disease induced mortality rate	0.00003 (0.000002–0.02); per day	10% over 10 years [6, 7]
𝛽1	Exogenous transmission rate for infection from reservoir	0.53 (0.0–0.6); per day	[16, 17]
𝛽2	Endogenous transmission rate for infection from gut colonization	0.30 (0.0–0.4); per day	[15]
𝜑	Colonization rate with epidemic strain	0.02 (0.0–0.2); per day	10% in first 5 days of life [8, 9, 11]
𝛾	Recovery rate	0.2 (0.13–0.33); per day	Days for successful clearance = 5 (3–8) days [21]
𝜎	Fomite generation rate	10.2 (3.6–17.3); per day	Based on NICU hand hygiene, colonization, survival, and transmission studies [8, 22, 23]§
𝜀	Fomite decay rate	78.0 (77.0–79.0); per day	𝜀=ln2/𝑡1/2 where C. parapsilosis half-life (𝑡1/2 ) on hands = 12.8 minutes [23]
𝑟	NICU readmission rate	0.343 (0.159–0.4); per day	[20, 24]
𝑑	Discharge rate	0.029 (0.020–0.294) per day	Adjusted length of stay = 34.3 (3.4–49.0) days [20, 25]
𝑝	Handwashing compliance proportion	0.40	[26]
ℎ	Handwashing efficacy	0.90	[26]
𝑞	Cohorting probability	0.80	[27]
𝑛	Neonate to nursing ratio	3	[27]
𝛼1	Colonization reduction efficacy	0.63^† 0.64^‡	[28–31]
𝛼2	Infection reduction efficacy	0.88^† 0.79^‡	[28–31]
𝜋	Prophylaxis proportion	0.29	[32]

^§𝜎= (probability of effective transmission from hand to object per contact) × (prevalence of C. parapsilosis on healthcare worker hands) × (average number of direct contacts with neonate in NICU per day).
^†Selective digestive decontamination (SDD) prophylaxis.
^‡Systemic antifungal prophylaxis.