Question

Please match the factors on the left to best describe the mechanism that contributes to the epidemic of the disease listed on the right. (Each answer option can be used only ONCE.)

-A.B.C. reservoir species -A.B.C. Antigenic shift to jump between species -A.B.C. counterattack to host’s immune system

A. typhoid fever pandemic in New York during the 1900s B. H5N1 and H7N9 epidemic in Asian countries C. Acquired Immunodeficiency Syndrome (AIDS) epidemic in human society

Answer 1

As Antigenic shift occurs in Influenza virus. It is an abrupt drastic discontinuous variation in the antigenic structure resulting in novel virus strain unrelated antigenically to predecessor strains. It can involve hemagglutinin, neuraminidase or both. Antibodies to predecessor strains do not neutralize the new variants and can therefore spread widely in the population causing major epidemics or pandemics. It occurs by genetic reassortment. Because of this H5N1 and H7N9 epidemics were seen in Asian countries.

AIDS virus once enters the host body, principally attacks the CD4 lymphocytes. The T4 cells decrease in number with the reversal of T4:T8 (helper: suppressor) cells ratio. Infected T4 cells do not release normal amounts of interleukin 2, gamma interferon and other cytokines suppressing cell mediated immune response.

In 1900s there was Typhoid Epidemic in USA. It was believed that Mary Mallon, a chef, was the reservoir for this infection. Reservoir means any human, animal, plant, food source, water source, soil or substance in which the disease causing agent is living and multiplying normally. It may or may not infect the reservoir. She was a healthy carrier of Salmonella typhi. When many cases in the USA were found to be linked with her, she was quarantined.

Answers A-A, B-B, C-C.