There are four other reasons why Australian authorities want to know about a person's travel history: terrorism, crime, drug trafficking and disease control (biosecurity).
A person who's travel history includes countries such as: Nigeria (in particular Borno), Chad, Mali, Syria, Iraq, Pakistan or Afghanistan would raise questions as to why has the applicant recently been to those locations.
Regarding disease control Australia is very serious about keeping all "exotic" diseases out of the country. It's one of the reasons it has very strict regulations regarding quarantine requirements for animals entering the country. In May 2022, an outbreak of foot and mouth disease occurred in Indonesia, much to the concern of the Australian authorities and livestock farmers.
In addition to diseases that could affect livestock and its native animals the authorities would like to know if anyone has been in regions where diseases of significance have occurred, such as: Ebola, tuberculosis, mosquito borne diseases such as zika virus, chikungunya, malaria, dengue and Japanese encephalitis, amongst others.
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