A weakly positive tuberculosis antibody does not mean a current infection with tuberculosis and is not infectious. An erythema of less than 5 mm at the site of intradermal injection of tuberculin is a negative result, indicating that there is no tuberculosis infection and no BCG vaccination. An erythema of 5-10 mm at the injection site is a weakly positive result, suggesting a previous TB infection. If the erythema is 10-20 mm, it is a positive result, which means the same as a weak positive result, that the person has been infected with TB or has received BCG vaccination. A strong positive result is only indicated by the presence of erythema >2cm or blisters, nodules, or rupture at the site of the tuberculin test, which may be a patient with current tuberculosis infection and needs to be treated in isolation at a designated hospital.