Pane zvikonzero zvakawanda zvekuvharirwa kwegumbo, uye izvo zvinonyanya kuzivikanwa varwere vane marara akasiyana-siyana akashata, kunyanya maronda akaipa emudumbu. Maererano nehuwandu husina kukwana, inenge 30% yevarwere vane matumbo egumbo vachasangana nemhando dzakasiyana-siyana dzekudzivirira, izvo zvinotungamirira zvakananga kukusakwanisa kwevarwere kudya nguva dzose, pamwe chete nemarwadzo emimba, kuputika, uye mumamiriro ezvinhu akaoma, kupera kwegumbo, uye kunyange. mamiriro ezvinhu anotyisa.