How many error are there in the following sentence? $$\begin{gathered} \underset{1}{\overset{Certain}{\to }}infections\underset{2}{\overset{are}{\to }}made by \underset{3}{\overset{both}{\to }}viral and bacterial elements that \underset{4}{\overset{makes}{\to }}tratement of those \underset{5}{\overset{infections}{\to }} \\ difficult. \end{gathered}$$