Small portion of contigs have high coverage

Question

[Md Moinuddin]

Hi,

I have mapped NCLDV (giant virus) contigs to the trimmed reads. A lot of reads (around 40%) getting mapped to the contigs, which is very high because in the metagenomic samples these viruses are not abundant. Then I looked into the coverage of each contigs. Among around 800000 contigs, only around 5000 contigs have very high coverage (that means most of the reads are getting mapped only to these small portion of contigs). Interestingly, these contigs have high coverage across all the samples. What can be the probable explanation?

Thanks in advance!