COVID-19 and dengue co-infection in Brazil: optimal control and cost-effectiveness analysis A. Omame, H. Rwezaura, M. L. Diagne, S. C. Inyama and J. M. Tchuenche Eur. Phys. J. Plus, 136 10 (2021) 1090 Published online: 29 October 2021 DOI: 10.1140/epjp/s13360-021-02030-6