Why mosquitoes can’t spread HIV (& diseases they DO spread)

Mosquitoes are no less pesky than the common fly. What makes them worse, though, is that they are considered the deadliest animals on Earth—killing more people every year than any other organism.

Mosquitoes can carry several deadly viruses, such as malaria, dengue fever, and West Nile virus. A question raised by many people is whether uncommon diseases are transmitted through blood, like HIV.

The Inability of Mosquitoes to Transmit HIV

Fortunately, mosquitoes don’t carry or spread the HIV virus. They can’t spread HIV primarily thanks to the anatomy and digestive system of mosquitos. We’ll explain more about this in the next sections.

Mosquito anatomy

The needle of a mosquito is composed of six parts. To bite or pierce the skin of an animal or human, four of these parts are used. The other two consist of two tubes. The first tube injects saliva into the host and the latter sucks the blood out to the mosquito. This is the primary reason why HIV cannot be transmitted through a mosquito. Humans are only injected with saliva.

Mosquito digestion system

If there was any trace of the HIV virus inside a mosquito, it would get digested in the gut.

Unlike other mosquito-related diseases, the HIV virus cannot replicate inside the mosquito’s gut and is broken down. HIV replicates in humans by binding to T cells.

These T cells don’t exist within the mosquito’s gut and therefore have no way to travel to the salivary glands of a mosquito.

HIV particles are digested with the blood meal by mosquitos and during this digestion process, the HIV virus is completely destroyed.

Circulation of HIV in humans

For diseases transmitted by a mosquito to be spread from person to person, the specific virus must circulate at sufficient levels within the blood of the host.

​HIV circulates at significantly low levels in human blood than required for the creation of a new infection. Hypothetically, if a mosquito were to inject HIV blood into a human, it would take approximately 10 million mosquito bites to carry a single unit of HIV. The average human with HIV positive carries around ten units of the virus.

Interrupted while feeding

If a mosquito’s feeding is interrupted, it moves on to the next host and resumes its meal.

An AIDS-free host squashes the mosquito as it attempts to feed and smears HIV-contaminated blood into the wound. In theory, any of the mosquito-borne viruses could be transmitted in this manner providing the host circulated sufficient virus particles to initiate re-infection by contamination.

The Risk through Physical Transmission?

Many people wonder about the risk of catching HIV through the physical injection of a mosquito alone. Often the mosquito’s blood feasting is interrupted. When this happens, the mosquito simply moves onto the next host victim, with traces of the blood from the previous person still around its mouth. It is commonly believed that this leftover blood may contain HIV.

To debunk this sloppy seconds theory, the chances of this is highly unlikely.

First, the second host victim must be extremely close to the previous HIV-positive person for the mosquito to quickly hop from one to the next.

Second, there isn’t a large percentage of detectable levels of HIV in HIV-positive people. Modern medicine is helping to further decrease this percentage. The probability of the needle of the mosquito making direct contact with the HIV virus in the bloodstream in just one piercing is highly unlikely.

Although it might not seem like it, a mosquito doesn’t consume a lot of blood during one sitting, and an even smaller percentage of this meal is left as residue on their mouthparts. According to the AIDS journal, the HIV virus was unable to penetrate membrane-enclosed blood sacks when this scenario was replicated in laboratories by scientists.

Mosquitoes are not syringes

The misconception that the needle of a mosquito works the same way as a hypodermic syringe is incorrect. While many people are aware that mosquitoes transfer saliva before feeding, they are unaware that the salivary canal is separate from the food canal and it’s a two-way road.

Behind the needle-like apparatus is a complex structure that is different than an uncomplicated syringe. The mosquito has two tubes; one for saliva and the other for drawing blood. The two are not interchangeable and the remnants of the last blood meal are not flushed out as done with a used needle.

Common Myths

Swallowing a mosquito by accident does not lead to HIV infection. Again, the HIV-positive blood content is insufficient to cause a new infection.

The same goes for squashing a mosquito. Many fear that any blood residue on the human skin after killing a mosquito is infectious. It’s not. Even if it gets in contact with an open wound, it again doesn’t have the required HIV content to cause any damage. As long as the blood is outside the host, it can’t do any damage anyway.

When a mosquito transfers a disease from one host to another, the virus must stay alive in the mosquito’s gut until the transfusion is completed. If the parasite is digested, which is usually what happens, then the cycle of transmission is interrupted and the parasite is terminated. It simply can’t be passed on.

How Do Mosquitoes Transmit Other Diseases?

Mosquitoes are able to spread certain diseases like malaria because the said virus is able to replicate inside the mosquito after an infected person is bitten.

The disease is mostly concentrated in the saliva of the mosquito which is injected into host victims through one of the mouthpart tubes when biting. Thankfully, this is not the case with HIV, making this transmission mode impossible.

Precautionary Measures

Even though the transmission of HIV through mosquitoes is overruled, they are still highly dangerous blood-sucking creatures.

Mosquitoes thrive in warm weather and basically trace humans by their carbon dioxide emissions, meaning that larger people and heavy inhalers are more prone to mosquito bites.

Mosquito repellant

A number of specially-formulated and effective repellants are on the market. Apply the tonic to all exposed skin surfaces when in the great outdoors, especially during the night. Be sure to apply it before your sunscreen at daytime.

All-natural solution

If you have allergies or strong reactions to repellents, then consider non-chemical alternatives such as natural plant oils such as Citronella. Some people swear by Vitamin B and Tea Tree oil for repelling mosquitos. Experiment and try natural solutions which are suitable for your skin type while being effective.

Wear loose clothing that covers properly

One of the simplest ways to prevent mosquito bites is to cover your skin. Wearing long sleeves and loose bottoms will not only be comfortable in humid, hot weather but also, sometimes mosquitoes are able to pierce through skin tight clothing and into the skin, especially if the fabric is of light material.

It’s a good idea to splurge on specially-designed shirts and pants that are lightweight but strong. These are mostly available in camping or sports stores and provide the best protection against mosquito bites while maintaining ease of wear.

A thrifty alternative is to spray the clothes you already own with a solution/repellant with Permethrin or similar repellant ingredient.

Mosquitoes are attracted to sweat

Excessive perspiration attracts mosquitoes, although not fresh sweat. Sweat that has dried up on the human skin, broken down into its ammonia component by bacteria, is what mosquitoes love. Fun fact: The most despised smell on earth is the most adored smell by mosquitoes – unwashed smelly socks.

Mosquito Nets

Mosquito nets are an affordable tried and tested method for keeping mosquitos at bay. Mosquito nets have holes large enough to allow breezes to pass through but small enough to keep insects out.

Hang or drape the netting over your bed and secure it to more than one surface. Make sure it is in a dome/tent-like shape without bearing down on the sleeper. Sleep away from the netting as mosquitoes can sometimes bite through the netting.

Holes must be checked regularly and darned or patched up using duct tape. For babies, use a carrier covered with mosquito netting, making sure that the edges are tightly fit with an elastic edge.

Don’t let water stand

Mosquitoes, unfortunately, exist all over the world except in extremely cold regions. But the creation of their favorite kinds of habitats to breed in should be avoided. Some hot spots for mosquitoes are:

• Swimming pools.
• Areas with waterlogged land.
• Industrial containers.
• Construction trenches or ditches.
• Sewage systems.
• Clogged storm drains.
• Don’t allow water to accumulate and stand near your home.
• If you have a pool or a kiddy pool, drain it or cover it up when not in use.
• Treat sewages, pools, etc. with chemical additives such as chlorine.