Will Zika explode across the US as it did elsewhere Housing in US better so people if they choose can avoid contact with A aegypti mosquitoes A aegypti restricted to Florida and Gulf Coast but A albopictus could play a role so vectors not wide spread across the US Cities here are less conducive to mosquito development fewer larval habitats Effective mosquito control efforts can be mobilized here So a major Zika outbreak is unlikely in the US But new viruses are lurking as we all know now Zoonotic virus diseases transmitted to humans by mosquitoes Species in the genus Culex are commonly involved Reservoirs typically birds but sometimes small mammals Humans are dead end hosts Eastern Equine Encephalitis EEE A bird disease that cycles through Culiseta melanura That mosquito will not bite humans but keeps the virus cycling in nature But other bridge mosquito vectors get infected from birds and will bite people or horses and emus making these dead end hosts sick A mosquito cannot pick up virus from a dead end host EEE is mostly an issue with horses human cases are rare but if occur are very serious EEE 270 human cases 1964 2010 21 cases in 2005 Case fatality rate 35 serious neurological impairment 35 No vaccine available LAC is unique in that it is only mosquito borne virus with vertical transmission mother to eggs this is common in ticks but not insects Vector Ae triseriatus Reservoir squirrels SLE Another bird disease with humans as a dead end host Last major epidemic outbreak 1975 1977 2 500 cases in 35 states Virtually no cases in last 20 years But West Nile Virus vectors Culex quinquefasciatus SE pipiens NE tarsalis West are major vectors Reservoir birds crows Humans are dead end host West Nile virus Intrinsic incubation in people period 5 15 days Only 1 500 to 1 1000 infections result in serious clinical symptoms symptoms of a severe infection may be marked by high fever severe headache neck stiffness stupor disorientation tremors convulsions muscle weakness paralysis and coma Almost all original cases were in elderly patients with compromised immune function but more recently healthy adults have been seriously impacted Japanese encephalitis Leading cause of encephalitis in Asia 30 50 000 cases yr Case fatality rate 30 range 0 3 to 60 Serious neurologic disease 30 however are subclinical Incubation period 5 15 days Vector Culex tritaeniorhynchus group Reservoirs wild birds domestic pigs Good news an attenuated virus vaccine is available Symptoms acute encephalitis can progress to paralysis seizures coma death most infects Factors associated with Mosquito related viral epidemic outbreaks Large populations develop of non immune virus na ve reservoir animals e g humans or birds Large populations of suitable vector mosquitoes develop from rainy years more human created larval habitats Virus is then introduced which is hard to predict So viral diseases tend to erupt and then subsequently decline but then lurk in the background The right conditions for an outbreak tend to occur cyclically e g every 15 20 years and spottily only in certain places Calculating metrics of infection Determination of the infection threshold titer of virus that results in at least 5 of the Determination of the extrinsic incubation days in this study mosquitoes infected so need enough virus in blood for mosquitoes to get infected period how long after ingesting virus does it take until the mosquito can transmit around 12 Can mosquitoes transmit HIV Studies show that HIV ingested by mosquitoes is simply digested and the virus does not survive to penetrate the gut wall replicate and migrate to the salivary glands i e biological transmission is not possible HIV circulates at very low titers in the human bloodstream and a mosquito has very little blood on the outside of its mouthparts after feeding So minimal chance of HIV being on proboscis Mechanical transmission is very very unlikely studies estimate a 1 10 000 000 chance A mosquito proboscis is not like a hypodermic needle Blood is sucked up through one canal and saliva delivered via another canal Flow is unidirectional A mosquito will not inject blood from a previous meal into a second host so can t be transmitted that way Under any realistic scenario that can be devised the answer to the above question is NO Very likely applies even more to COVID which is not even blood borne