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Typhus bacilli, paratyphoid bacilli


Typhoid fever is an infectious disease caused by the typhus bacillus, while paratyphoid is caused by the paratyphoid bacillus.
From the Showa period to after World War II, these two infectious diseases were extremely common in Japan. Since this time, the number of patients infected with either disease has declined dramatically. Most of the victims of these diseases today are people returning from trips to other Asian countries and Africa, but domestic cases of transmission are still seen.

How is infection caused?

Both of these diseases only occur in humans. They are transmitted orally via food and water contaminated by the stool of infected individuals, including those who show no symptoms (oral infection).
Compared with other types of salmonella, the amount of bacteria required to cause gastroenteritis is relatively low. Example foods which can cause infection include raw shellfish such as oysters as well as salads.

What are the symptoms of typhus/paratyphoid infection?

The incubation period for the typhus bacillus is 3 days to 3 months (normally 1 to 3 weeks), while the incubation period for the paratyphoid bacillus is 1 to 5 weeks (normally 10 to 14 days). Both diseases cause high fevers of 38° C or higher, but as they otherwise have no particularly distinctive symptoms, it is frequently difficult to make a diagnosis.
Symptoms can include bradycardia (slow pulse), roseola (rose-like red spots), and splenoma (swollen spleen).

Bureau of Public Health, Tokyo Metropolitan Government
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