In the affected district of Howrah, avian flu spread to Panchla in addition to Sankrail. Reports from the district said a fox and other birds like falcon were found dead there.
The above comments describe likely spread of H5N1 to additional species in the Calcutta suburbs that have tested positive for H5N1 (see satellite map here and here).

Although West Bengal has not confirmed H5N1 in additional species, Bangladesh has reported H5N1 confirmation in massive crow deaths in north and south Bangladesh. Videos of initial outbreaks in Birbhum also showed large numbers of dead crows in regions where poultry died. Similarly, crow deaths have been described in multiple regions in West Bengal.

The spread of H5N1 to these additional species hampers control of H5N1. Although Calcutta has been sealed, the additional species provide vectors that can navigate over and through poultry checkpoints on Calcutta's borders.

Similarly, these wild species also impacts control of H5N1 at the borders with neighboring districts or countries. Although alerts have been issued and checkpoints have been increased, further spread of H5N1 is likely and excessive poultry deaths suggest H5N1 has already crossed into adjacent districts and countries.

More extensive testing and reporting in these border areas would be useful.