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interferon: microspectrophotometric quantitation of cyto› pathic effecf’, Appln Environ. Microbial., 31, 35-38, (1996), the contents of which are incorporated by reference, was used. The dose needed to reduce virus CPE by 50% (EC$_{50}$ ) is determined from this dye uptake. Compounds considered active by CPE inhibition and by NR dye uptake were tested again using a VY reduction assay. The effect on reduction of virus yield was assessed by assaying frozen and thawed eluates from each micro well for virus titer by serial dilution onto monolayers ofMDCK cells. A known active drug is run in parallel as a positive control. Since PSMA was found to be a potent inhibitor of multiple strains of influenza in tissue culture experiments, it was also tested against human strains of virus adapted to grow in mice (strains NWS/33 and Victoria/37/75 in Table 15). 

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*The different assay formats include cytopathic effect (CPE), virus yield reduction (VY) and neutral red (NR) uptake. 

[0364] In vivo, in a dose fmding toxicity study efficacy evaluation, PSMA was administered intranasally to mice using the dose schedule shown in Table 16. In this study, mice were dosed twice a day with 50 ul of test material for five days, and then observed for a total of 21 days. The results after 14 days are presented in Table 16. 

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* Survivors at day 14. 

## Example 21 

[0365] From the data obtained in the dose ranging study above, three concentrations of PSMA were found to be acceptable for dosing in an in vivo efficacy analysis, that is, 50 ul twice a day of PSMA at 0.3, 0.1 and 0.03 mg/ml. 

[0366] As used herein, unless indicated to the contrary, % refers to percentage by weight. Unless indicated to the contrary, the singular refers to the plural and vice versa. 

[0367] The above embodiments and examples are given to illustrate the scope and spirit of the present invention. These embodiments and examples will make apparent, to those skilled in the art, other embodiments and examples. These other embodiments and examples are within the contempla› tion of the present invention. Therefore the present invention should be limited only by the appended claims. 

We claim: 

1. A method for the treatment or prevention of a viral, bacterial, or fungal infection in a host, which comprises administering to the host a therapeutically or prophylacti› cally effective amount of an anionic cellulose-based poly› mer, a prodrug thereof, or a pharmaceutically acceptable salt of said anionic cellulose based polymer or prodrug, wherein 

