Influenza is a viral infectious disease often causes fever, dyspnea and lung damage during the infection process, while some studies have found that algae extracts are beneficial to these symptoms. After infection, Gavage of Undaria pinnatifida fucoidan to mice were found
significantly reduce lung consolidation. The higher oral dose of Undaria pinnatifida fucoidan provided a significant level of protection against the clinical signs of influenza and lung consolidation in a mouse model when delivered three days prior to infection. Rhamnan sulfate showed potent antiviral activities against enveloped viruses based on the selectivity indices. Through plaque assay, rhamnan sulfate
inhibited the early steps of viral replication and targeted the influenza adsorption and penetration steps of viral replication. Rhamnan sulfate suppressed virus growth and promoted the production of virus-specific antibodies. Rhamnan sulfate is incorporated into the Peyer’s patch through the M cells, which possibly accounts for its ability to enhance antibody production. Algae extracts can reduce the damage caused by influenza virus and increase immunity. Therefore, Algae extracts can be used as a complimentary medicine for treatment.