TB is usually spread from one person to another by aerosol infection. The causative organism is found in airborne droplets. Name the species of the causative organism of TB that is commonly transferred from person to person by aerosol infection.
In general, countries without a BCG vaccination programme are high-income countries with a low number of TB cases. In most of these countries, the vaccine is offered only to babies and children at high risk of developing TB. Suggest one reason why a child in a country with a low number of cases of the disease might still be at high risk of developing TB.
The World Bank places countries into four income groups. Table 3.1 gives the estimated TB incidence from 2012 to 2016 for these groups. Incidence means the number of new TB cases occurring per 100000 people in a year. The new cases also include cases that occur again after recovery, known as relapse TB. Describe the patterns and trends shown in Table 3.1.
There is evidence that the BCG vaccine has also given protection against the disease leprosy. Leprosy is caused by a bacterium that is closely related to the bacteria that cause TB. Suggest why the BCG vaccine can also protect against leprosy.
A baby may acquire artificial active immunity to TB after receiving the BCG vaccine. A baby may also acquire natural passive immunity to TB. State the differences between artificial active immunity and natural passive immunity.