Hello Thanks for the query Single widal test is of no importance unless the titres are very high more than 320. A four fold rise in titre in comparison to previous one suggests typhoid. There are so many condition in which widal test is falsely positive, one of which is previous immunisation. You can go for typhidot test which is more suggestive of typhoid infection. Rise in temp. following heavy exercise or after other physical exertion is very common as that time there is production of heat by muscular contraction, but it should not persist long. As he is getting cough and cold every 3-4 week consult an E.N.T. doctor so that he will properly evaluate clinically and by lab. diagnosis to rule out various causes like sinusitis, chronic bronchitis as cause of cough and cold. Vaccination does not give 100% protection from typhoid although chances are very few but it can occur. I hope this answers your query well Wish you and your family good health With regards