freshclam: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/freshclam - from package: clamav

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/freshclam - from package: clamav-freshclam

You may install the required package with command apt-get install {package}

Error in other languages:
freshclam: bevel nie gevind nie
freshclam: comandă negăsită
freshclam: comando não encontrado
freshclam: commande introuvable
freshclam: command not found
freshclam: käsku ei ole
freshclam: không tìm thấy lệnh
freshclam: komanda nerasta
freshclam: Kommando nicht gefunden.
freshclam: kommandot finns inte
freshclam: komut yok
freshclam: nie znaleziono polecenia
freshclam: níor aimsíodh an t-ordú
freshclam: no se encontró la orden
freshclam: no s'ha trobat l'ordre
freshclam: opdracht niet gevonden
freshclam: parancs nem található
freshclam: perintah tidak ditemukan
freshclam: príkaz nenájdený
freshclam: příkaz nenalezen
freshclam: команда не найдена
freshclam: командата не е открита
freshclam: 命令找不到
freshclam: コマンドが見つかりません