The Israeli mosquito that brought the fever to America

Climate change helps to increase the distribution of mosquitoes in the world and you also the spread of viruses and epidemics. This is exactly what happened when a mosquito from Tel Aviv brought West Nile fever to the United States

By Maya Falah, Angle, Science and Environment News Agency

It seems that summer refuses to end for good and give way to winter, but little by little the temperatures start to drop. Many of us may bemoan the shortening of the daylight hours, but there is one thing that goes away with the end of summer that no one misses: the mosquitoes. The annoying buzzers that accompany us in almost all regions of the country during the hot months are not only annoying, but can also be dangerous: mosquitoes can carry viruses and epidemics with them; And not only that - we'll see that climate change makes it easier for them to spread throughout the planet, and bring various diseases (such as dengue fever, West Nile fever, chikungunya, malaria and also Zika) to areas where they did not operate before.

This week, representatives of 197 countries will gather in Bonn, Germany, at the annual UN climate summit (COP 23), where they will discuss ways to successfully implement the Paris Agreement on climate change, which was signed in December 2015. One of the important topics that will be discussed in Bonn is the impact of climate change on our health and ways to prepare to the new reality.

Many studies They show that in recent decades the distribution of different types of mosquitoes has been expanding to countries and continents where they were not seen before. The mosquitoes can travel long distances in their early life stages by sailing or flying, all they need to survive the journey is less than an inch of standing water. If the conditions in the country they arrive at are suitable for them, they will survive the transition and perhaps even reproduce and spread.

Tel Aviv-New York line

A good example of how climate change causes disease to spread around the world is the way West Nile disease has attacked North America. Prof. Jürgen May, head of the infectious diseases department at the Bernard-Nocht Institute for Tropical Diseases in Germany (BNITM), says that this is exactly how West Nile fever - a disease observed in Israel as early as the 50s - came from Israel to the United States.

The virus was first observed in the United States in New York in 1999. "It is possible to say with a high level of confidence that the virus arrived via a mosquito carrying the disease on board a plane that took off from Tel Aviv," says May, who adds in an interview with "Angle" that the researchers came to this conclusion afterhomology tests (which test the existence of a common genetic branch) and genetic analysis of the virus that spread in the USA showed that it is genetically very close to a virus that was discovered a year earlier in the brain of a goose on a farm in Israel.

According to May, a chain of conditions made the spread of the disease at the destination possible. "It was a mild winter at the time and this fact allowed the mosquitoes to survive until spring," May explained. "At the beginning of the season, the summer was hot and dry, which played in favor of the mosquitoes. They stung migrating birds, which in turn carried the virus far into the continent. The end of the summer was rainy and wet, and caused the appearance of many habitats that are suitable for the breeding of mosquitoes.' And from there the rest is history: the virus is widespread today in many areas of the United States, and every year thousands of cases of infection are reported in the country."

West Nile fever, which is still common in our country and is not transmitted from person to person (but only by mosquito bites), is a disease that manifests itself in flu-like symptoms (fever, headaches, joint pains and sometimes nausea and diarrhea). According to the Ministry of Health, usually dozens of its cases are reported in Israel per year (in 2000, however, its outbreak resulted in 400 reported cases), mainly in the months of August-October. Like the flu, it is dangerous mainly for sensitive populations such as the elderly and those with a damaged immune system, but unlike the flu - there is currently no vaccine that can prevent infection with the disease.

It doesn't just end with West Nile fever: following the Asian tiger mosquito, for example - which arrived in Europe via Croatia in the 70s, and is also increasingly common in our country in recent years - cases of dengue fever (which used to be common in the equatorial regions and especially in Africa) have already been observed along the coasts Croatia and also on the island of Madeira in the Atlantic Ocean; And last summer, Italy also suffered from an outbreak of the chikungunya disease it transmits - a disease that causes fever, headaches and severe joint pain that can continue even months later.

The summer is getting longer and the mosquitoes are celebrating

According to the experts, an increase of several temperatures in the global average according to the expected forecasts will not particularly affect the outbreak of mosquitoes and their diseases, but unusual weather conditions for the season, on the other hand, will have a great effect. These unusual conditions open the way for mosquitoes to survive and breed, and climate change is making such events more and more common. One of the phenomena we have seen in recent years is the lengthening of the hot season and the shortening of the transition seasons, a fact that helps mosquitoes and the diseases they carry not only to thrive, but also to spread to places where they were not common before.

Extreme weather events, such as heat waves for example, contribute to the proliferation of mosquitoes and allow them to spread diseases more easily: mosquitoes multiply in hot temperatures, as do the viruses and diseases they transmit. "Heat waves are definitely an advantage for the mosquitoes," says Dr. Jonas Schmidt, virologist at BNITM. "In hot periods there are more mosquitoes, and each mosquito carries with it more viruses." Since the mosquito has no ability to control its body temperature, when the temperatures drop its body cools down - and so does the virus. This makes it much less active, and below a certain temperature also does not allow it to survive or reproduce.

Apply, dress and dry

So what can be done to protect yourself from mosquitoes? The climate change is already here, and according to all the predictions, heat waves are going to be regular visitors to us, and the summer is also expected to start early and gradually end later. Nevertheless, there are things we can do to try to prevent them from spreading en masse: it is very important to pay attention and make sure that there are no stagnant water sources around our living areas. Even a dish of a flower pot with leftover irrigation water can provide them with a fertile ground to raise their offspring, guaranteeing us a house or yard full of mosquitoes.

In addition, the Ministry of Environmental Protection and the Ministry of Health suggest during the summer and transition seasons to apply mosquito repellent preparations on all parts of the body when staying outside in the evening and to try to wear long clothing; In the area of ​​the house, they recommend installing mosquito repellent devices and making sure to use them according to the instructions, installing tight nets on the windows that will prevent mosquitoes from entering and making sure to close the house's doors after dark.

See more on the subject on the science website:

• The diseases spread by climate change
• The mosquitoes will save us from... the mosquitoes
• The genome of the Nile fever mosquito was deciphered