Mosquitoes carrying ‘twin viruses’, causing co-infection

Tribune News Service

Naina Mishra

Chandigarh, November 25

The Post-Graduate Institute of Medical Education and Research’s (PGI) Virology Department has found incidences of Aedes aegypti mosquito carrying both dengue and chikungunya viruses at the same time during vector-borne transmission this season. Due to a common vector, both dengue and chikungunya viruses are co-infecting the human host as well.

The UT has so far witnessed 101 cases of chikungunya and 839 of dengue. “This season, Aedes mosquitoes have been found carrying dengue or chikungunya singly or even both, but in lesser percentage of cases,” says Prof RK Ratho, Head of Virology Department.

Overlapping symptoms

• Symptoms such as high-grade fever, headache, nausea, rashes and body pain are common to both infections
• What sets chikungunya infection apart is severe joint pain, which can persist for a few months to a year
• Severe chikungunya infection can cause neurological, optical manifestations
• Chikungunya is usually non-fatal, while dengue fever may result in severe complications, including death

Same Aedes species vector for both

• Co-infection can occur due to bite by a mosquito infected with both viruses or by two mosquitoes, infected with a separate dengue and chikungunya viruses
• Same Aedes aegypti species can transmit both viruses. These viruses can replicate simultaneously in mosquito
• This mosquito bites in day, especially in morning and evening hours, and prefers to breed around human dwellings

Cases in UT this season

839 Dengue
101 Chikungunya

A concurrent viral infection in humans occurs due to the bite of a mosquito infected with both viruses or bites by two different mosquitoes, each infected with a separate virus — dengue virus (DENV) and chikungunya virus (CHIKV).

Both viruses are transmitted by the same Aedes mosquito species. These viruses are able to replicate simultaneously in the mosquito, which has the ability to deliver concomitantly infectious particles of dengue and chikungunya viruses in a single bite via saliva.

A secondary infection with the chikungunya virus can be introduced in mosquitoes that have a primary infection with dengue virus.

Prof Ratho says: "It has been seen Aedes aegypti happens to be the primary vector species for the transmission of dengue disease. Similarly, the same mosquito also possesses the capacity to transmit chikungunya virus. Sometimes, the mosquito is found harbouring both infections simultaneously. This mosquito is a day bitter, more so in the morning and evening hours and prefers to breed around the human dwellings."

Both dengue and chikungunya viral infections have many common clinical presentations such as high-grade fever, headache, nausea, rashes and body pain.

The most prominent feature of chikungunya infection is the severe joint pain, which sometimes can persist for a few months to a year. A severe chikungunya viral infection can cause neurological and optical manifestations. Thus, chikungunya viral infection is usually non-fatal, while dengue fever may result in severe complications, including death. Therefore, co-infection with the two viruses may result in disease with overlapping symptoms.

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