Based on parameters from Martínez et al., NEJM 2020 · Updated to MV Hondius context, May 2026 📘 Educational tool, not for prediction — explore how R₀, isolation timing, and population size affect outbreak dynamics
Basic reproduction number R₀ ?Average number of secondary infections from one infected individual in a fully susceptible population. NEJM paper: 2.12 pre-isolation2.12
Above R = 1 the epidemic grows; below R = 1 it declines. The discrete change models the moment isolation measures take effect.
Model limitations
Structural (deterministic SEIR)
Homogeneous, perfectly mixed population — ignores cabin structure, shared meals, work shifts
No super-spreaders: the NEJM paper shows 3 patients caused 64% of secondary cases — heterogeneity not captured by SEIR
With small populations (e.g., ship with 147 people), stochastic effects dominate — same configuration can yield very different outcomes
R₀ changes discretely and instantly on control day — in reality it's gradual and partially followed
No age structure (the paper shows positive correlation between age and viral load)
Parameter uncertainties
R₀ = 2.12 is the median from a single outbreak (34 cases); 95% credible interval 1.24–3.35 — wide
CFR = 32% from rural Argentinian context with limited ICU access; not validated for advanced healthcare settings
Mean incubation of 23 days used as exponential rate (1/23 per day): real distribution is an asymmetric gamma, not exponential
Post-control R₀ fixed at 0.96 (from Epuyén 2018–19): not verifiable for MV Hondius
No diagnostic delay: in reality, cases are identified days after infection, distorting real-time R estimates
Completely missing
No zoonotic transmission (relevant in endemic settings, but not on the ship)
No external case importation into the simulated population
No hospital capacity as a variable influencing CFR
No pre-existing immunity (ANDV is rare enough to assume a naive population)
No spatial or contact network modeling (who is where on the ship, who shares bathrooms or dining areas)
MV Hondius situation (May 9, 2026)
Cases: 6 confirmed, 3 suspected, 3 deaths (WHO DON599). Current observed CFR (~50%) is based on N too small to be significant
Index case is a Dutch citizen exposed in Argentina (road trip Nov 2025 – Apr 2026): zoonotic source known, not from prior unknown human transmission
Passengers of 24 nationalities dispersed across multiple countries: international contact tracing ongoing but data incomplete
WHO: global risk low. CDC USA: response level 3 (lowest). No evidence of transmission outside close contacts
Genomic sequencing of the variant not yet publicly available for this cluster
Purpose of this tool
This simulator is an educational and exploratory tool, not a predictive model. It helps qualitatively understand how epidemic trajectories change with key parameters — particularly the effect of control measures (Control day slider) and population size. It allows comparison of extreme scenarios (no control vs. immediate isolation) and visualizes the logic of the reproduction number R: when R drops below 1, the epidemic extinguishes regardless of existing cases. Do not use this to make quantitative predictions about the MV Hondius outbreak or for public health decisions. Those require stochastic models calibrated on local real-time data, with explicit contact structure and Bayesian parameter estimation.
Sources: Martínez et al., NEJM 2020 (doi:10.1056/NEJMoa2009040) · WHO Disease Outbreak News DON599, May 4, 2026 · CDC Hantavirus Situation Summary, May 9, 2026 · Wikipedia MV Hondius hantavirus outbreak (updated May 9, 2026).