Are you one of these people who loathes spending time outdoors at dusk as the weather warms and mosquitoes start biting?

Female mosquitoes need blood to develop their eggs. Even though they take a tiny amount of our blood, they can leave us with itchy red lumps that can last days. And sometimes something worse.

So why does our body react and itch after being bitten by a mosquito? And why are some people more affected than others?

What happens when a mosquito bites?

Mosquitoes are attracted to warm blooded animals, including us. They’re attracted to the carbon dioxide we exhale, our body temperatures and, most importantly, the smell of our skin.

The chemical cocktail of odours from bacteria and sweat on our skin sends out a signal to hungry mosquitoes.

Some people’s skin smells more appealing to mosquitoes, and they’re more likely to be bitten than others.

Once the mosquito has made its way to your skin, things get a little gross.

The mosquito pierces your skin with their “proboscis”, their feeding mouth part. But the proboscis isn’t a single, straight, needle-like tube. There are multiple tubes, some designed for sucking and some for spitting.

Once their mouth parts have been inserted into your skin, the mosquito will inject some saliva. This contains a mix of chemicals that gets the blood flowing better.

There has even been a suggestion that future medicines could be inspired by the anti-blood clotting properties of mosquito saliva.

It’s not the stabbing of our skin by the mosquito’s mouth parts that hurts, it’s the mozzie spit our bodies don’t like.

Are some people allergic to mosquito spit?

Once a mosquito has injected their saliva into our skin, a variety of reactions can follow. For the lucky few, nothing much happens at all.

For most people, and irrespective of the type of mosquito biting, there is some kind of reaction. Typically there is redness and swelling of the skin that appears within a few hours, but often more quickly, after just a few minutes.

Occasionally, the reaction can cause pain or discomfort. Then comes the itchiness.

Some people do suffer severe reactions to mosquito bites. It’s a condition often referred to as “skeeter syndrome” and is an allergic reaction caused by the protein in the mosquito’s saliva. This can cause large areas of swelling, blistering and fever.

The chemistry of mosquito spit hasn’t really been well studied. But it has been shown that, for those who do suffer allergic reactions to their bites, the reactions may differ depending on the type of mosquito biting.

We all probably get more tolerant of mosquito bites as we get older. Young children are certainly more likely to suffer more following mosquito bites. But as we get older, the reactions are less severe and may pass quickly without too much notice.

How best to treat the bites?

Research into treating bites has yet to provide a single easy solution.

There are many myths and home remedies about what works. But there is little scientific evidence supporting their use.

The best way to treat mosquito bites is by applying a cold pack to reduce swelling and to keep the skin clean to avoid any secondary infections. Antiseptic creams and lotions may also help.

There is some evidence that heat may alleviate some of the discomfort.

It’s particularly tough to keep young children from scratching at the bite and breaking the skin. This can form a nasty scab that may end up being worse than the bite itself.

Applying an anti-itch cream may help. If the reactions are severe, antihistamine medications may be required.

To save the scratching, stop the bites

Of course, it’s better not to be bitten by mosquitoes in the first place. Topical insect repellents are a safe, effective and affordable way to reduce mosquito bites.

Covering up with loose fitted long sleeved shirts, long pants and covered shoes also provides a physical barrier.

Mosquito coils and other devices can also assist, but should not be entirely relied on to stop bites.

There’s another important reason to avoid mosquito bites: millions of people around the world suffer from mosquito-borne diseases. More than half a million people die from malaria each year.

In Australia, Ross River virus infects more than 5,000 people every year. And in recent years, there have been cases of serious illnesses caused by Japanese encephalitis and Murray Valley encephalitis viruses.

Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Before the COVID pandemic, the World Health Organization (WHO) had made a list of priority infectious diseases. These were felt to pose a threat to international public health, but where research was still needed to improve their surveillance and diagnosis. In 2018, “disease X” was included, which signified that a pathogen previously not on our radar could cause a pandemic.

While it’s one thing to acknowledge the limits to our knowledge of the microbial soup we live in, more recent attention has focused on how we might systematically approach future pandemic risks.

Former US Secretary of Defense Donald Rumsfeld famously talked about “known knowns” (things we know we know), “known unknowns” (things we know we don’t know), and “unknown unknowns” (the things we don’t know we don’t know).

Although this may have been controversial in its original context of weapons of mass destruction, it provides a way to think about how we might approach future pandemic threats.

Influenza: a ‘known known’

Influenza is largely a known entity; we essentially have a minor pandemic every winter with small changes in the virus each year. But more major changes can also occur, resulting in spread through populations with little pre-existing immunity. We saw this most recently in 2009 with the swine flu pandemic.

However, there’s a lot we don’t understand about what drives influenza mutations, how these interact with population-level immunity, and how best to make predictions about transmission, severity and impact each year.

The current H5N1 subtype of avian influenza (“bird flu”) has spread widely around the world. It has led to the deaths of many millions of birds and spread to several mammalian species including cows in the United States and marine mammals in South America.

Human cases have been reported in people who have had close contact with infected animals, but fortunately there’s currently no sustained spread between people.

While detecting influenza in animals is a huge task in a large country such as Australia, there are systems in place to detect and respond to bird flu in wildlife and production animals.

It’s inevitable there will be more influenza pandemics in the future. But it isn’t always the one we are worried about.

Attention had been focused on avian influenza since 1997, when an outbreak in birds in Hong Kong caused severe disease in humans. But the subsequent pandemic in 2009 originated in pigs in central Mexico.

Coronaviruses: an ‘unknown known’

Although Rumsfeld didn’t talk about “unknown knowns”, coronaviruses would be appropriate for this category. We knew more about coronaviruses than most people might have thought before the COVID pandemic.

We’d had experience with severe acute respiratory syndrome (SARS) and Middle Eastern respiratory syndrome (MERS) causing large outbreaks. Both are caused by viruses closely related to SARS-CoV-2, the coronavirus that causes COVID. While these might have faded from public consciousness before COVID, coronaviruses were listed in the 2015 WHO list of diseases with pandemic potential.

Previous research into the earlier coronaviruses proved vital in allowing COVID vaccines to be developed rapidly. For example, the Oxford group’s initial work on a MERS vaccine was key to the development of AstraZeneca’s COVID vaccine.

Similarly, previous research into the structure of the spike protein – a protein on the surface of coronaviruses that allows it to attach to our cells – was helpful in developing mRNA vaccines for COVID.

It would seem likely there will be further coronavirus pandemics in the future. And even if they don’t occur at the scale of COVID, the impacts can be significant. For example, when MERS spread to South Korea in 2015, it only caused 186 cases over two months, but the cost of controlling it was estimated at US$8 billion (A$11.6 billion).

The 25 viral families: an approach to ‘known unknowns’

Attention has now turned to the known unknowns. There are about 120 viruses from 25 families that are known to cause human disease. Members of each viral family share common properties and our immune systems respond to them in similar ways.

An example is the flavivirus family, of which the best-known members are yellow fever virus and dengue fever virus. This family also includes several other important viruses, such as Zika virus (which can cause birth defects when pregnant women are infected) and West Nile virus (which causes encephalitis, or inflammation of the brain).

The WHO’s blueprint for epidemics aims to consider threats from different classes of viruses and bacteria. It looks at individual pathogens as examples from each category to expand our understanding systematically.

The US National Institute of Allergy and Infectious Diseases has taken this a step further, preparing vaccines and therapies for a list of prototype pathogens from key virus families. The goal is to be able to adapt this knowledge to new vaccines and treatments if a pandemic were to arise from a closely related virus.

Pathogen X, the ‘unknown unknown’

There are also the unknown unknowns, or “disease X” – an unknown pathogen with the potential to trigger a severe global epidemic. To prepare for this, we need to adopt new forms of surveillance specifically looking at where new pathogens could emerge.

In recent years, there’s been an increasing recognition that we need to take a broader view of health beyond only thinking about human health, but also animals and the environment. This concept is known as “One Health” and considers issues such as climate change, intensive agricultural practices, trade in exotic animals, increased human encroachment into wildlife habitats, changing international travel, and urbanisation.

This has implications not only for where to look for new infectious diseases, but also how we can reduce the risk of “spillover” from animals to humans. This might include targeted testing of animals and people who work closely with animals. Currently, testing is mainly directed towards known viruses, but new technologies can look for as yet unknown viruses in patients with symptoms consistent with new infections.

We live in a vast world of potential microbiological threats. While influenza and coronaviruses have a track record of causing past pandemics, a longer list of new pathogens could still cause outbreaks with significant consequences.

Continued surveillance for new pathogens, improving our understanding of important virus families, and developing policies to reduce the risk of spillover will all be important for reducing the risk of future pandemics.

This article is part of a series on the next pandemic.

Allen Cheng, Professor of Infectious Diseases, Monash University

This article is republished from The Conversation under a Creative Commons license. Read the original article.