If this is of interest to you: Measurement of 50 % egg infectious dose (EID50)

The EID50 of influenza virus was determined as previously described (Huprikar and Rabinowitz, 1980). Briefly, serial 10-fold dilutions of the virus were prepared in PBS, and 100 μl of each dilution was inoculated into the chorio-allantoic cavities of 10-days-old embryonated chicken eggs. The eggs were incubated at 34 °C for 48 h. Four eggs were infected with each virus dilution. Harvested allantoic fluid was tested for HA activity using 0.5 % tRBC.

read:

Quantitation of influenza virus using field flow fractionation and multi-angle light scattering for quantifying influenza A particles

Tatiana Bousse, David A. Shore, Cynthia S. Goldsmith, M. Jaber Hossain, Yunho Jang, Charles T. Davis, Ruben O. Donis, James Stevens J Virol Methods. J Virol Methods. 2013 Nov; 193(2): 589–596. Published online 2013 Jul 31. doi: 10.1016/j.jviromet.2013.07.026

This is a rather interesting question and somewhat related topics have been discussed on several platforms. One brief source that could be of relevancy albeit with approximation is https://www.sciencegateway.org/protocols/cellbio/cell/moipfu.htm where appropriate definition can be found and approximate relations have been derived.

Otherwise, an even closely related study is by Bousse et la. 2013 PMID: 23916678 Article Quantitation of influenza virus using field flow fractionati...

Good luck!