Extrinsic Incubation Period (EIP) refers to the amount of time that it takes for a virus to infect the midgut and disseminate to the saliva.

Extrinsic Incubation Period

This variable is dependent on different mosquito species. Different species vary in their blood feeding behavior and host preference. For example, the Aedes aegypti mosquito reside near urban areas and feed upon human hosts.

Probability of Host being Fed Upon

The vectorial capacity of mosquitoes is mostly influenced by these variables:
- extrinsic incubation period
- probability of mosquito daily survival
- probability of a host being fed upon

University of California, Davis

Mosquitoes are one of the most important vectors of arboviruses. Common viruses transmitted by mosquitoes: dengue, zika, yellow fever, chikungunya, and many others. 

Mosquitoes and Emerging Pathogens

Rückert, Claudia, and Gregory D Ebel. “How Do Virus-Mosquito Interactions Lead to Viral Emergence?” Trends in Parasitology, U.S. National Library of Medicine, Apr. 2018, www.ncbi.nlm.nih.gov/pubmed/29305089. 

How do virus-mosquito interactions lead to viral emergence?

The vector competence of mosquitoes depends on the virus' ability to cross several physical barriers and antiviral responses within the mosquito:
- Midgut infection barrier
- Midgut escape barrier
- Salivary gland infection barrier
- Salivary gland escape barrier
- RNA interference

Mosquito Vector Competence

When a mosquito is taking a blood meal, it is possible to also ingest an arbovirus from an infected individual. The virus travels through the feeding tube, infects the midgut epithelium, and replicates in the midgut before entering the basal lamina and disseminate throughout the body. Then, the virus is able to infect the salivary gland, where it can be released into the saliva and infect the next host when the mosquito is taking another blood meal.

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