Superinfection exclusion is a phenomenon in which a preexisting viral infection prevents a secondary infection with the same or a closely related virus. This phenotype is often poorly understood, and may reflect programmed virus superinfection or a kind of antiviral state of the infected cell.
Some bacterial viruses encode proteins to achieve superinfection exclusion. These viral proteins can interfere with DNA release into the host cytoplasm or modify the entry receptor. They can also act as inhibitors of viral peptidoglycan degradation enzymes thereby preventing entry of incoming phages 
.
Many viruses can make superinfection exclusion, few examples are described below:
| Family | Genus | Virus | Superinfection exclusion protein | strategy | references |
| Baculoviridae | Alphabaculovirus | AcMNPV | undocumented | undocumented |
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| Closteroviridae | Closterovirus | Citrus tristeza virus | p33 | undocumented | |
| Flaviridae | Hepacivirus | Hepatitis C | Undocumented | post entry |
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| Siphoviridae | Lambdalikevirus | Enterobacteria phage HK97 | gp15 | Undocumented |
|
| Siphoviridae | T5likevirus | Enterobacteria phage T5 | Lipoprotein Llp | Blocks T5 entry receptor FhuA |
|
| Myoviridae | T4likevirus | Enterobacteria phage T4 | Immunity protein Imm Protein spackle Sp |
Blocks DNA translocation into host cytoplasm Inhibits the lysozyme activity |
|
| Siphoviridae | unclassified | Bacteriophage TP-J34 | Lipoprotein LTP | Blocks DNA ejection into host cytoplasm |
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| Siphoviridae | unclassified | Lactococcus phage Tuc2009 | ORF2 | Blocks DNA ejection into host cytoplasm |
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| Podoviridae | P22likevirus | Enterobacteria phage P22 | SieA | Blocks DNA translocation into host cytoplasm |
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| Myoviridae | Punalikevirus | Enterobacteria phage P1 | Sim | Probably blocks DNA translocation into host cytoplasm |
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