Have used ClamAv and ClamTK for sometime and they usually had been excellent. Since update to 16.04 ClamTK has stopped offering threat removal and one has to resort to command-line AV scanner.
Wonder if that is a general issue or I need to look for a fix.
HI @Al_Salem,
have you done a full system update as mine works no problem!:
Yes, update and upgrade are applied on regular basis.
HI @Al_Salem,
try changing your software sources download location and updating again, it might help?. 
Did many of that and purge reinstall. May be a user account issue.
installed files according to synaptic ClamTK propertie :
/.
/usr
/usr/bin
/usr/bin/clamtk
/usr/share
/usr/share/applications
/usr/share/applications/clamtk.desktop
/usr/share/doc
/usr/share/doc/clamtk
/usr/share/doc/clamtk/README.gz
/usr/share/doc/clamtk/changelog.Debian.gz
/usr/share/doc/clamtk/copyright
/usr/share/help
/usr/share/help/C
/usr/share/help/C/clamtk
/usr/share/help/C/clamtk/about.page
/usr/share/help/C/clamtk/analysis-general.page
/usr/share/help/C/clamtk/analysis-overview.page
/usr/share/help/C/clamtk/av-wizard-help.page
/usr/share/help/C/clamtk/bugreport.page
/usr/share/help/C/clamtk/figures
/usr/share/help/C/clamtk/figures/clamtk-analysis-previous.png
/usr/share/help/C/clamtk/figures/clamtk-analysis-results.png
/usr/share/help/C/clamtk/figures/clamtk-analysis.png
/usr/share/help/C/clamtk/figures/clamtk-check-updates.png
/usr/share/help/C/clamtk/figures/clamtk-hidden-files.png
/usr/share/help/C/clamtk/figures/clamtk-history.png
/usr/share/help/C/clamtk/figures/clamtk-interface.png
/usr/share/help/C/clamtk/figures/clamtk-large-files.png
/usr/share/help/C/clamtk/figures/clamtk-nautilus.png
/usr/share/help/C/clamtk/figures/clamtk-network.png
/usr/share/help/C/clamtk/figures/clamtk-pua.png
/usr/share/help/C/clamtk/figures/clamtk-quarantine.png
/usr/share/help/C/clamtk/figures/clamtk-recursive.png
/usr/share/help/C/clamtk/figures/clamtk-results-negative.png
/usr/share/help/C/clamtk/figures/clamtk-results-positive.png
/usr/share/help/C/clamtk/figures/clamtk-scheduler1.png
/usr/share/help/C/clamtk/figures/clamtk-settings.png
/usr/share/help/C/clamtk/figures/clamtk-update1.png
/usr/share/help/C/clamtk/figures/clamtk-update2.png
/usr/share/help/C/clamtk/figures/clamtk-update3.png
/usr/share/help/C/clamtk/figures/clamtk-update4.png
/usr/share/help/C/clamtk/figures/clamtk-whitelist.png
/usr/share/help/C/clamtk/figures/clamtk-wizard.png
/usr/share/help/C/clamtk/general-scanning.page
/usr/share/help/C/clamtk/hidden-preferences.page
/usr/share/help/C/clamtk/history.page
/usr/share/help/C/clamtk/index.page
/usr/share/help/C/clamtk/installation.page
/usr/share/help/C/clamtk/large-files-preferences.page
/usr/share/help/C/clamtk/proxy-preferences.page
/usr/share/help/C/clamtk/pua-preferences.page
/usr/share/help/C/clamtk/quarantine.page
/usr/share/help/C/clamtk/recursive-preferences.page
/usr/share/help/C/clamtk/results.page
/usr/share/help/C/clamtk/scan-preferences.page
/usr/share/help/C/clamtk/scheduler.page
/usr/share/help/C/clamtk/start-preferences.page
/usr/share/help/C/clamtk/translation.page
/usr/share/help/C/clamtk/update-gui.page
/usr/share/help/C/clamtk/update-preferences.page
/usr/share/help/C/clamtk/update-signatures.page
/usr/share/help/C/clamtk/whitelist.page
/usr/share/locale
/usr/share/locale/af
/usr/share/locale/af/LC_MESSAGES
/usr/share/locale/af/LC_MESSAGES/clamtk.mo
/usr/share/locale/ar
/usr/share/locale/ar/LC_MESSAGES
/usr/share/locale/ar/LC_MESSAGES/clamtk.mo
/usr/share/locale/ast
/usr/share/locale/ast/LC_MESSAGES
/usr/share/locale/ast/LC_MESSAGES/clamtk.mo
/usr/share/locale/az
/usr/share/locale/az/LC_MESSAGES
/usr/share/locale/az/LC_MESSAGES/clamtk.mo
/usr/share/locale/bg
/usr/share/locale/bg/LC_MESSAGES
/usr/share/locale/bg/LC_MESSAGES/clamtk.mo
/usr/share/locale/bs
/usr/share/locale/bs/LC_MESSAGES
/usr/share/locale/bs/LC_MESSAGES/clamtk.mo
/usr/share/locale/ca
/usr/share/locale/ca/LC_MESSAGES
/usr/share/locale/ca/LC_MESSAGES/clamtk.mo
/usr/share/locale/cs
/usr/share/locale/cs/LC_MESSAGES
/usr/share/locale/cs/LC_MESSAGES/clamtk.mo
/usr/share/locale/da
/usr/share/locale/da/LC_MESSAGES
/usr/share/locale/da/LC_MESSAGES/clamtk.mo
/usr/share/locale/de
/usr/share/locale/de/LC_MESSAGES
/usr/share/locale/de/LC_MESSAGES/clamtk.mo
/usr/share/locale/el_GR
/usr/share/locale/el_GR/LC_MESSAGES
/usr/share/locale/el_GR/LC_MESSAGES/clamtk.mo
/usr/share/locale/en_AU
/usr/share/locale/en_AU/LC_MESSAGES
/usr/share/locale/en_AU/LC_MESSAGES/clamtk.mo
/usr/share/locale/en_CA
/usr/share/locale/en_CA/LC_MESSAGES
/usr/share/locale/en_CA/LC_MESSAGES/clamtk.mo
/usr/share/locale/en_GB
/usr/share/locale/en_GB/LC_MESSAGES
/usr/share/locale/en_GB/LC_MESSAGES/clamtk.mo
/usr/share/locale/es
/usr/share/locale/es/LC_MESSAGES
/usr/share/locale/es/LC_MESSAGES/clamtk.mo
/usr/share/locale/eu
/usr/share/locale/eu/LC_MESSAGES
/usr/share/locale/eu/LC_MESSAGES/clamtk.mo
/usr/share/locale/fi
/usr/share/locale/fi/LC_MESSAGES
/usr/share/locale/fi/LC_MESSAGES/clamtk.mo
/usr/share/locale/fo
/usr/share/locale/fo/LC_MESSAGES
/usr/share/locale/fo/LC_MESSAGES/clamtk.mo
/usr/share/locale/fr
/usr/share/locale/fr/LC_MESSAGES
/usr/share/locale/fr/LC_MESSAGES/clamtk.mo
/usr/share/locale/ga
/usr/share/locale/ga/LC_MESSAGES
/usr/share/locale/ga/LC_MESSAGES/clamtk.mo
/usr/share/locale/gl
/usr/share/locale/gl/LC_MESSAGES
/usr/share/locale/gl/LC_MESSAGES/clamtk.mo
/usr/share/locale/he
/usr/share/locale/he/LC_MESSAGES
/usr/share/locale/he/LC_MESSAGES/clamtk.mo
/usr/share/locale/hr
/usr/share/locale/hr/LC_MESSAGES
/usr/share/locale/hr/LC_MESSAGES/clamtk.mo
/usr/share/locale/hu
/usr/share/locale/hu/LC_MESSAGES
/usr/share/locale/hu/LC_MESSAGES/clamtk.mo
/usr/share/locale/id
/usr/share/locale/id/LC_MESSAGES
/usr/share/locale/id/LC_MESSAGES/clamtk.mo
/usr/share/locale/it
/usr/share/locale/it/LC_MESSAGES
/usr/share/locale/it/LC_MESSAGES/clamtk.mo
/usr/share/locale/ja
/usr/share/locale/ja/LC_MESSAGES
/usr/share/locale/ja/LC_MESSAGES/clamtk.mo
/usr/share/locale/km
/usr/share/locale/km/LC_MESSAGES
/usr/share/locale/km/LC_MESSAGES/clamtk.mo
/usr/share/locale/ko
/usr/share/locale/ko/LC_MESSAGES
/usr/share/locale/ko/LC_MESSAGES/clamtk.mo
/usr/share/locale/lo
/usr/share/locale/lo/LC_MESSAGES
/usr/share/locale/lo/LC_MESSAGES/clamtk.mo
/usr/share/locale/lt
/usr/share/locale/lt/LC_MESSAGES
/usr/share/locale/lt/LC_MESSAGES/clamtk.mo
/usr/share/locale/lv
/usr/share/locale/lv/LC_MESSAGES
/usr/share/locale/lv/LC_MESSAGES/clamtk.mo
/usr/share/locale/mr
/usr/share/locale/mr/LC_MESSAGES
/usr/share/locale/mr/LC_MESSAGES/clamtk.mo
/usr/share/locale/ms
/usr/share/locale/ms/LC_MESSAGES
/usr/share/locale/ms/LC_MESSAGES/clamtk.mo
/usr/share/locale/nb
/usr/share/locale/nb/LC_MESSAGES
/usr/share/locale/nb/LC_MESSAGES/clamtk.mo
/usr/share/locale/nl
/usr/share/locale/nl/LC_MESSAGES
/usr/share/locale/nl/LC_MESSAGES/clamtk.mo
/usr/share/locale/nl_BE
/usr/share/locale/nl_BE/LC_MESSAGES
/usr/share/locale/nl_BE/LC_MESSAGES/clamtk.mo
/usr/share/locale/nn
/usr/share/locale/nn/LC_MESSAGES
/usr/share/locale/nn/LC_MESSAGES/clamtk.mo
/usr/share/locale/pa
/usr/share/locale/pa/LC_MESSAGES
/usr/share/locale/pa/LC_MESSAGES/clamtk.mo
/usr/share/locale/pl
/usr/share/locale/pl/LC_MESSAGES
/usr/share/locale/pl/LC_MESSAGES/clamtk.mo
/usr/share/locale/pt
/usr/share/locale/pt/LC_MESSAGES
/usr/share/locale/pt/LC_MESSAGES/clamtk.mo
/usr/share/locale/pt_BR
/usr/share/locale/pt_BR/LC_MESSAGES
/usr/share/locale/pt_BR/LC_MESSAGES/clamtk.mo
/usr/share/locale/ro
/usr/share/locale/ro/LC_MESSAGES
/usr/share/locale/ro/LC_MESSAGES/clamtk.mo
/usr/share/locale/ru
/usr/share/locale/ru/LC_MESSAGES
/usr/share/locale/ru/LC_MESSAGES/clamtk.mo
/usr/share/locale/si
/usr/share/locale/si/LC_MESSAGES
/usr/share/locale/si/LC_MESSAGES/clamtk.mo
/usr/share/locale/sk
/usr/share/locale/sk/LC_MESSAGES
/usr/share/locale/sk/LC_MESSAGES/clamtk.mo
/usr/share/locale/sl
/usr/share/locale/sl/LC_MESSAGES
/usr/share/locale/sl/LC_MESSAGES/clamtk.mo
/usr/share/locale/sr@latin
/usr/share/locale/sr@latin/LC_MESSAGES
/usr/share/locale/sr@latin/LC_MESSAGES/clamtk.mo
/usr/share/locale/sv
/usr/share/locale/sv/LC_MESSAGES
/usr/share/locale/sv/LC_MESSAGES/clamtk.mo
/usr/share/locale/ta
/usr/share/locale/ta/LC_MESSAGES
/usr/share/locale/ta/LC_MESSAGES/clamtk.mo
/usr/share/locale/te
/usr/share/locale/te/LC_MESSAGES
/usr/share/locale/te/LC_MESSAGES/clamtk.mo
/usr/share/locale/th
/usr/share/locale/th/LC_MESSAGES
/usr/share/locale/th/LC_MESSAGES/clamtk.mo
/usr/share/locale/tr
/usr/share/locale/tr/LC_MESSAGES
/usr/share/locale/tr/LC_MESSAGES/clamtk.mo
/usr/share/locale/ug
/usr/share/locale/ug/LC_MESSAGES
/usr/share/locale/ug/LC_MESSAGES/clamtk.mo
/usr/share/locale/uk
/usr/share/locale/uk/LC_MESSAGES
/usr/share/locale/uk/LC_MESSAGES/clamtk.mo
/usr/share/locale/uz
/usr/share/locale/uz/LC_MESSAGES
/usr/share/locale/uz/LC_MESSAGES/clamtk.mo
/usr/share/locale/zh_CN
/usr/share/locale/zh_CN/LC_MESSAGES
/usr/share/locale/zh_CN/LC_MESSAGES/clamtk.mo
/usr/share/locale/zh_TW
/usr/share/locale/zh_TW/LC_MESSAGES
/usr/share/locale/zh_TW/LC_MESSAGES/clamtk.mo
/usr/share/man
/usr/share/man/man1
/usr/share/man/man1/clamtk.1.gz
/usr/share/menu
/usr/share/menu/clamtk
/usr/share/perl5
/usr/share/perl5/ClamTk
/usr/share/perl5/ClamTk/Analysis.pm
/usr/share/perl5/ClamTk/App.pm
/usr/share/perl5/ClamTk/Assistant.pm
/usr/share/perl5/ClamTk/GUI.pm
/usr/share/perl5/ClamTk/History.pm
/usr/share/perl5/ClamTk/Network.pm
/usr/share/perl5/ClamTk/Prefs.pm
/usr/share/perl5/ClamTk/Quarantine.pm
/usr/share/perl5/ClamTk/Results.pm
/usr/share/perl5/ClamTk/Scan.pm
/usr/share/perl5/ClamTk/Schedule.pm
/usr/share/perl5/ClamTk/Settings.pm
/usr/share/perl5/ClamTk/Shortcuts.pm
/usr/share/perl5/ClamTk/Startup.pm
/usr/share/perl5/ClamTk/Update.pm
/usr/share/perl5/ClamTk/Whitelist.pm
/usr/share/pixmaps
/usr/share/pixmaps/clamtk-kde.png
/usr/share/pixmaps/clamtk-kde.xpm
/usr/share/pixmaps/clamtk.png
/usr/share/pixmaps/clamtk.xpmHi Al,
sorry but that doesn’t really help me at all!. 
Try the following terminal command (Ctrl + Alt + t) and then a restart and see if it helps:
sudo apt-get update && sudo apt get remove calmav clamtk && sudo apt-get install clamav clamtk
Tried remove and reinstall as above and am currently on – uname -a $HP-Pavilion-dv2700-Notebook-PC 4.4.0-36-generic #55-Ubuntu SMP Thu Aug 11 18:00:59 UTC 2016 i686 athlon i686 GNU/Linux.
Yet has to use command line clamscan to remove malware. Nonetheless, can use clamtk GUI to update freshclam.