1 Faculty of Medicine, Universidad Católica de la Santísima Concepción, Concepción, Chile.
2 Faculty of Health Science, Universidad Autónoma de Chile, Talca, Chile.
3 Research Group AIDS and Other Infectious Diseases, Faculty of Health Sciences, Universidad Tecnológica de Pereira, Pereira, Colombia. Electronic address: arodriguezm@utp.edu.co.