Close-up photo of a mosquito drawing blood from skin
IanDagnall Computing/Alamy Stock Photo

Meet the World's Deadliest Creature

What makes mosquitoes so deadly? And how can they be stopped?

By Maggie Mead
From the May/June 2024 Issue

Learning Objective: Students will describe how mosquitoes can harm human health and evaluate solutions to this problem.

Lexile: 850L; 530L
Other Focus Areas: Engineering, Measurement & Data
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All About Mosquitoes
Watch a video about mosquitoes.

Our planet is filled with fearsome creatures. Car-sized hippos have jaws strong enough to shatter bones. Scorpions use piercing tails to inject victims with deadly venom. Pythons strangle their prey with ropelike bodies.

But which animal on Earth is the deadliest to humans? It’s actually none of those creatures. It’s the mosquito!

You might think of these buzzing insects as just an annoying part of spring and summer. In the U.S., their bites are usually no worse than an itchy red bump that fades in a few days or weeks.

However, in many areas of the world, mosquito bites are a serious concern. They commonly spread dangerous diseases, like malaria. Mild malaria cases cause headaches, fevers, and chills. Without treatment, the disease can be deadly. Each year, malaria and other diseases spread by mosquitoes kill more than 750,000 people. Sadly, most of those who die are kids.

Scientists have come up with many ways to protect humans from mosquitoes. But lately, the methods haven’t been working very well. Disease-causing mosquitoes are now thriving in parts of the world they haven’t been found in before.

In the U.S., mosquitoes are showing up earlier each year and staying longer,” says Russanne Low. She’s a scientist who studies mosquitoes. Low is one of many people working to spread the news about the dangers of mosquitoesand share ideas for how people can help.

Meet the Mosquito

There are more than 110 trillion mosquitoes on Earth. That’s almost 16,000 for every person! They live on every continent except Antarctica.

Mosquitoes are famous bloodsuckers. So you might be surprised that the insects’ main food source is nectar, a sweet liquid from plants. There are more than 3,500 mosquito species. Different species feed on blood from different animals. Only a small portion of species feed on human blood.

Male mosquitoes don’t bite at all. That’s the job of female mosquitoesjust before they lay eggs. When temperatures rise above 50°F (10°C), female mosquitoes lay eggs in watery areas, like ponds, puddles, or rain-filled flowerpots. But before they do, the insects need a blood meal. They search for an animal, like a human, and use their tube-shaped mouth like a straw to suck up blood.

This is where the problem begins.

When a mosquito bites, it injects saliva into its victim. If the mosquito has recently bitten a person infected with a disease like malaria, that spit can contain a tiny germ that causes the disease. When this germ enters a person’s blood, they become infected too.

That’s how, bite by itchy bite, millions of people come down with malaria each year. Millions more are infected with other deadly diseases, such as dengue (DENG-gee) and West Nile virus.

An Ancient Battle

Humans’ battle with mosquitoes isn’t new (see Malaria-Stopping Strategies, below). As long as we have walked on Earth, mosquitoes have been biting usand infecting us with diseases. For most of that time, people thought the illnesses were caused by warm, moist air. That made sense because the diseases were most common near swamps, where mosquitoes like to breed.

In the late 1800s, scientists discovered the tiny parasite that causes malaria and learned it was spread by mosquitoes. Researchers went on to develop drugs to help treat the disease. They also created insecticides, chemicals that can kill mosquitoes. Thanks to these innovations, malaria was mostly gone from the U.S. by the 1950s.   

But the fight against malaria has continued in much of Africa and other places with tropical climates, where mosquitoes lay eggs year-round. In these areas, people spray their homes with insecticides. They sleep under mosquito nets to prevent the insects from biting them at night.

Over time, the efforts helped. Malaria remained a major killer in Africa, but by 2019, deaths from the disease dropped to the lowest number in history.

Mosquitoes Fight Back

Unfortunately, in recent years, malaria deaths have gone up again. Why? Scientists are finding some mosquito-fighting strategies are no longer working very well. The reason: Mosquitoes have adapted.

Here’s how that happened: Over time, the chemicals in insecticides have killed many mosquitoesbut not all of them. Some survived, passing down their insecticide-beating traits to their young. Over time, more and more mosquitoes carried traits that protected them from insecticides. As a result, these chemicals are no longer as effective against mosquitoes.

In Africa, mosquito nets have long protected people from the insects at night. But scientists suspect that some mosquitoes there have adapted to bite in the daytime. “It’s a constant cycle,” says Low. “We have a solution, then they adapt to it.”

There’s another problem. Dangerous mosquitoes are moving around the world. Since 2012, a type of mosquito from South Asia has been spreading malaria in African cities. And for the first time in many years, mosquitoes have infected people in parts of Europe with dengue.

In the U.S., several dangerous mosquito species are thriving. They are originally from other areas of the world and are more aggressive than native species. The insects feed more often and bite quickly, making them hard to shoo away in time. These mosquitoes can spread diseases like malaria.

Scientists expect these problems to get worse because of climate change. As temperatures warm, mosquitoes can survive year-round in places that were once too cold for them. That means more parasites and germs that cause diseases.

Taking Action

Luckily, scientists are hard at work developing solutions. Eric Ochomo is an entomologist, or insect scientist, in the East African country of Kenya. Malaria is a constant threat there. He’s testing out new and improved tools to fight mosquitoes.

One tool is an indoor device that sends out a chemical into the air. The chemical confuses mosquitoes so they don’t bite. Ochomo is also testing an outdoor device that lures the insects with sweet liquid, then kills them with poison. Using several strategies is important, Ochomo says. That makes it less likely that mosquitoes will adapt.

Other researchers are breeding male mosquitoes that can’t reproduce. In the wild, these mosquitoes could help lower the mosquito population since they can’t reproduce. And in late 2023, a new malaria vaccine was introduced in parts of Africa. Scientists expect the shot to reduce malaria deaths, especially in kids.

There are ways people like you can help (see How You Can Help, below). Ochomo hopes more kids become scientists when they grow up, so they can help protect humans from mosquitoes.

There are a lot of problems we still don’t know how to solve,” he says. “We need all the brains we can get!”

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Slideshows (1)
Slideshow
Vocabulary Slideshow

<p>View this slideshow to explore the STEM vocabulary in &quot;Meet the World's Deadliest Creature.&quot;</p>

Vocabulary Slideshow

View this slideshow to explore the STEM vocabulary in "Meet the World's Deadliest Creature."

Step-by-Step Lesson Plan

1. PREPARE TO READ (15 minutes)
Connect prior knowledge with information presented in a video.

  • Show the cover of the magazine. Review each animal shown and ask students the question it poses: “Can you spot the deadliest animal?” Tally the predictions, and have students explain their thinking. Once you have reviewed their predictions, reveal that the deadliest animal to humans is the mosquito.
  • Write the heading Mosquito Facts on the board and share an image of a mosquito. Have students think and then share what they know about mosquitoes. Record information students share on the board.
  • Play the All About Mosquitoes video. Return to your list of facts to include more details, revise them, or include new information learned. (e.g., “Mosquitoes feed on bloodmight becomeFemales of some mosquito species feed on human blood.”)

2. READ AND SUMMARIZE (30 minutes)
Identify text structures and evaluate their purpose.

  • Preview the STEM vocabulary with the Vocabulary Slideshow. Distribute the Identifying Text Structures activity, reviewing the types of text structures as needed. Then read the article aloud, pausing at the end of each section to discuss and identify that section’s text structure. Have students complete the activity in pairs.
  • Revisit the class list of mosquito facts, adding additional facts and updating information based on the article. For a low-stakes assessment, have students complete the No-Sweat Bubble Test, referring to the article as needed.

3. RESPOND TO READING (30 minutes)
Observe schoolyard conditions to determine if there is habitat for mosquito larvae.

  • Discuss as a class and ask: What would happen if you removed the standing water where female mosquitoes lay eggs? (They would die, and soon there would be fewer adult mosquitoes.)
  • Share the Mosquito Habitat Survey investigation. Before heading outside, discuss which parts of the school’s surroundings students will visit and discuss behavior expectations. Have groups complete Part 1 outside. Reconvene after they complete the activity to share results and discuss any follow-up actions.
  • If you wish, you can report your results to scientists using NASA’s GLOBE Mosquito Habitat Mapper apphttps://observer.globe.gov/do-globe-observer/mosquito-habitats.

Text-to-Speech