According to the passage, typhus is commonly found ---- .

Typhus used to be known as "jail fever" because it
was frequent in prisons; but overcrowding,
poverty, and bad hygienic surroundings anywhere
are suitable conditions for epidemics of typhus.
Improved conditions in industrialised countries
have made it unusual, since typhus is carried from
one person to another by infected body lice.
Typhus comes on suddenly with a rise in
temperature to about 39 °C, but within four days it
may be as high as 42 °C. There may, or may not,
be a rash at this time, and in the second week,
when the temperature is at its highest, there is
delirium, physical weakness, and a weak pulse.