Citrus fruits, vitamin D, and the RNA virus: A correlation and meta-analysis study in Taiwan and the USA

•RNA viruses are significant threats to the world's public health.•It is anticipated that vitamin D will have strong immunomodulatory effects by suppressing the replication of RNA virus in the host.•Citrus fruits and their secondary metabolites have the power to boost antibodies against RNA viruses.•The effects of both Citrus fruits along with its secondary metabolites and Vitamin D were compared with the research and review articles available across the USA and Taiwan.