"Alfred Geskin" asked about the possibility of a virus infecting his fern...
> Is this likely to be a virus, and should I discard the two infected
> or is removing infected leaves a valid method of control?
It's hard to know if the symptoms you describe have a viral origin. There
is not a lot of information on fern viruses, although I believe a couple of
the groups including members with broader host ranges, like the potyviruses,
and perhaps the tobamoviruses, are known to infect some ferns. Viruses from
these groups are mechanically transmitted, and so, may be spread to to other
plants by handling infected material. Also, removing leaves is unlikely to
control the infection, because the virus is usually located throughout the
entire plant, even the parts that do not show symptoms.