Draft: Added measles

Added the Measles class, extended from the SARS-CoV-2 class. Only the transmissibility_factor value is changing between these two classes, controlled by the DataRegistry.

Two new cases were added:

• Measles-R12, with transmissibility factor of 0.07
• Measles-R18, corresponding to the worst case scenario with transmissibility factor of 0.047.

Explanation:

• In the model, SARS-CoV-2-OMICRON is 5 times more transmissible than the original strain (transmissibility factor is 1/5 = 0.2).
• According to this reference, the effective reproduction number of Omicron ranges from 2.42 to 5.11, with a pool estimate of 4.2.
• For measles, R0 is often cited to be 12-18, which means that each person with measles would, on average, infect 12-18 other people in a totally susceptible population (ref).
• Therefore, the Omicron R0 was adjusted to measles by multiplying the Omicron R0 by a factor of 2.86 (=12/4.2) for the lower bound R0 of measles (12) and of 4.29 (=18/4.2) for the upper bound R0 of measles.
• In the end, the transmissibility factor for measles if 1/(5 * 2.86) = 0.07 for the lower bound R0 and (1/(5 * 4.29) for the upper bound R0.

Note that WP3 schema was not updated to include this new parameter, even though the model is prepared to handle such inclusion. Upon merge of this MR, data schema in QA will be updated.

Disabled VE (host immunity) values for these new Virus.