OBJECTIVES: Wars, pandemics, and disasters that cause societal instability are referred to as “Big Events” and have been associated with outbreaks of infectious diseases. At the initiation of the 2008 severe economic recession in Greece (the last Big-Event before the pandemic), a hepatitis C virus (HCV) outbreak emerged among people who inject drugs (PWID) in 2009, which was the root of the 2010 Human Immunodeficiency Virus (HIV) outbreak. The HCV-outbreak was not detected, while that of HIV was identified in mid-2011. Given that HCV and HIV share common transmission routes, the HIV-interventions directly reduced the HIV-incidence by 78% and indirectly HCV-incidence by 64.8%. This study aims to assess what would have been the course of the two outbreaks, and their economic consequences if the 2009 HCV-outbreak had been timely detected.

METHODS: A published, stochastic, dynamic model was used to simulate HCV and HIV transmission among PWID (Gountas et al. IJDP 2020, Gountas et al. PLOS 2021). The model was calibrated to reproduce the observed epidemiological parameters among PWID of Athens, Greece. The time-horizon of the analysis was 2002-2019 to capture second-order transmission effects.

RESULTS: Under the status-quo scenario, the cumulative HCV and HIV cases were 6480 (95% CrI: 6000, 6900) and 1360 (95% CrI: 400, 2600), respectively. If the HCV outbreak had been detected and integrated interventions had been initiated in 2009 or 2010, 440 and 970 new HCV cases and 740 and 1110 new HIV cases could have been averted by 2019, respectively. Concerning the costs of treating the new cases for both diseases, the existence of an efficient notification system would have saved €40.9-65.8 million by 2019.

CONCLUSIONS: An accurate automated outbreak detection system among PWID is a cost-saving investment. During the COVID-19 pandemic, which is the current Big Event, HIV/HCV surveillance should be more intense to timely detect new outbreaks.