Insect vectors of human viral diseases: can they transmit COVID-19?

Many insects are naturally infected by a wide range of viruses and transmit viral diseases that cause significant morbidity and mortality to humans. Amongst insects, mosquitoes are the prominent vectors of viral diseases of which the genus Aedes is the most relevant species regarding disease transmission to humans. Mosquitoes mainly transmit the viruses of family Flaviviridae and the mosquito-borne Flavivirus diseases are the most serious and widespread. Many diseases have been caused by Flaviviruses of which Dengue viral infection and Japanese encephalitis are prominent in countries of the Asian region. Apart from the viruses of family Flaviviridae, mosquitoes also transmit viruses of families Togaviridae and Bunyaviridae, which however have caused disease outbreaks to a lesser extent than the Flaviviridae viruses. Insects other than mosquitoes transmit viral diseases to a lesser extent. Sand fly species of order Diptera transmits viruses of family Bunyaviridae, which causes Sand fly fever mainly in the countries of Europe and Africa. Insects such as cockroaches and fly species are also capable of causing viral diseases to humans, which however is by mechanical transmission, rather than the biological transmission evident in mosquitoes. Covid-19 is transmitted by a RNA virus of the family Coronaviridae, genus Coronavirus. There have been no reports of Covid-19 transmission by blood-sucking insects such as mosquitoes or any other such insects. However, the mechanical transmission of the virus is plausible by body parts of insects contacted with contaminated surfaces. The new coronavirus is mainly transmitted by respiratory droplets that are suspended in the air via breathing, coughing or sneezing of the infected persons. However, the virus has been detected in the feces of confirmed patients and insects in contact with or feeding on fecal surfaces may play a role in Covid-19 transmission. The coronavirus that is now threatening the world is constantly changing and subtly different from the one that first emerged in China. Everyday learning of the coronavirus and its transmission has refined our knowledge on combating it, and the role of insects in Covid-19 transmission cannot be entirely ruled out.