During the repeated Widal's agglutination test it was noticed that the ratio of antibody titers and O-antigens S.typhi in the patient's serum had increased from 1:100 to 1:400. How would you interpret these results?

Answer options

1. The patient previously had typhoid fever
2. The patient was previously vaccinated against typhoid fever
3. The patient has typhoid fever
4. The patient is an acute carrier of typhoid microbes
5. The patient is a chronic carrier of typhoid microbs