Trichomoniasis

Trichomoniasis (Trichomonas vaginalis) follows the SEIS pattern with a key feature: most women do not spontaneously clear the infection, leading to very long durations.

Class: sti.Trichomoniasis | Alias: 'tv' | Base class: SEIS

States and transitions

     ┌─────────────┐
     │ Susceptible │◄──────────────────────────────────────┐
     └──────┬──────┘                                       │
            │ infection (immediately infectious)            │
            │                                               │
            ├────────────────────┐                          │
            ▼                    ▼                          │
     ┌─────────────┐     ┌──────────────┐                  │
     │Asymptomatic │     │ Symptomatic  │                  │
     │  F: 60%     │     │  F: 40%      │                  │
     │  M: 50%     │     │  M: 50%      │                  │
     └──────┬──────┘     └──────┬───────┘                  │
            │                   │                           │
            │                   ▼                           │
            │            ┌───────────┐                      │
            │            │ Seeks care│                      │
            │            └───────────┘                      │
            │                                               │
            ├── 10% of F: natural clearance ───────────────┤
            │   (F: ~48 mo, M: ~26 wk)                     │
            │                                               │
            └── 90% of F: persistent infection              │
                M: natural clearance ──────────────────────┘

Parameters

Natural history

Parameter	Default	Description
`dur_exp`	0	No latent period
`p_symp`	[0.40, 0.50]	Probability of symptoms [F, M]
`dur_presymp`	F: [1 wk, 12 wk]; M: [0.25 wk, 1 wk]	Time to symptom onset [mean, std]
`dur_asymp2clear`	F: [48 mo, 6 mo]; M: [26 wk, 4 wk]	Duration of asymptomatic infection [mean, std]
`dur_symp2clear`	F: [20 wk, 4 wk]; M: [18 wk, 4 wk]	Duration of symptomatic infection [mean, std]
`p_clear`	0.10	Probability of spontaneous clearance in women
`dur_persist`	100 yr	Duration of persistent infection (effectively lifelong)

Care seeking

Parameter	Default	Description
`p_symp_care`	[0.39, 0.27]	Probability of seeking care if symptomatic [F, M]
`dur_symp2care`	F: [2 mo, 1 mo]; M: [1 wk, 2 wk]	Time from symptoms to care seeking [mean, std]

Transmission

Parameter	Default	Description
`beta_m2f`	0.1	Per-act male-to-female transmission probability
`rel_beta_f2m`	0.5	Female-to-male transmission relative to male-to-female
`beta_m2c`	None	Mother-to-child transmission probability
`beta_m2m`	None	Male-to-male transmission probability
`eff_condom`	0.0	Condom efficacy
`init_prev`	0.01	Initial prevalence