translation.en: Polio is caused by polioviruses, classified into types 1, 2 and 3. Humans are the only reservoir of infection:
translation.mt: Il-poljo hija kkawżata minn poljovirusijiet, ikklassifati f'tipi 1, 2 u 3. Il-bnedmin huma l-uniċi 'reservoir' tal-infezzjoni: