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.

You may have noticed that changes in weight are sometimes accompanied by changes in your period.

But what does one really have to do with the other?

Maintaining a healthy weight is key to regular menstruation. Here’s why – and when to talk to your doctor.

The role of hormones

The menstrual cycle – including when you bleed and ovulate – is regulated by a balance of hormones, particularly oestrogen.

The ovaries are connected to the brain through a hormonal signalling system. This acts as a kind of “chain of command” of hormones controlling the menstrual cycle.

The brain produces a key hormone, called the gonadotropin-releasing hormone, in the hypothalamus. It stimulates the release of other hormones which tell the ovaries to produce oestrogen and release a mature egg (ovulation).

But the release of the gonadotropin-releasing hormone depends on oestrogen levels and how much energy is available to the body. Both of these are closely related to body weight.

Oestrogen is primarily produced in the ovaries, but fat cells also produce oestrogen. This is why weight – and more specifically body fat – can affect menstruation.

Can being underweight affect my period?

The body prioritises conserving energy. When reserves are low it stops anything non-essential, such as reproduction.

This can happen when you are underweight, or suddenly lose weight. It can also happen to people who undertake intense exercise or have inadequate nutrition.

The stress sends the hypothalamus into survival mode. As a result, the body lowers its production of the hormones important to ovulation, including oestrogen, and stops menstruation.

Being chronically underweight means not having enough energy available to support reproduction, which can lead to menstrual irregularities including amenorrhea (no periods at all).

This results in very low oestrogen levels and can cause potentially serious health risks, including infertility and bone loss.

Missing periods is not always a cause for concern. But a chronic lack of energy availability can be, if not addressed. The two are linked, meaning understanding your period and being aware of any prolonged changes is important.

How about being overweight?

Higher body fat can elevate oestrogen levels.

When you’re overweight your body stores extra energy in fat cells, which produce oestrogen and other hormones and can cause inflammation in the body. So, if you have a lot of fat cells, your body produces an excess of these hormones. This can affect normal functioning of the uterus lining (endometrium).

Excess oestrogen and inflammation can interfere in the feedback system to the brain and stop ovulation. As a result, you may have irregular or missed periods.

It can also lead to pain (dysmenorrhea) and heavier bleeding (menorrhagia).

Being overweight can sometimes worsen premenstrual syndrome as well. One study found for every 1 kg increase in height (m²) in body mass index (BMI), the risk of premenstrual syndrome went up by 3%. Women with a BMI over 27.5 kg/m² had a much higher risk than those with a BMI under 20 kg/m².

What else might be going on?

Sometimes weight changes are linked to hormonal balances that indicate an underlying condition.

For example, people with polycystic ovary syndrome may gain weight or find it hard to lose weight because they have a hormonal imbalance, including higher levels of testosterone.

The syndrome is also associated with irregular periods and heavy bleeding. So, if you notice these symptoms, it’s a good idea to talk to your doctor.

Similarly, weight changes and irregular periods in midlife might signal the start of perimenopause, the period before menopause (when your periods stop altogether).

When should I worry?

Small changes in when your period comes or how long it lasts are usually harmless.

Similarly, slight fluctuations in weight won’t usually have a significant impact on your period – or the changes may be so subtle you don’t notice them.

But regular menstruation is an important marker of female health. Sometimes changes in flow, regularity or the pain you experience can indicate there’s something else going on.

If you notice changes and they don’t feel right to you, speak to a health care provider.

Mia Schaumberg, Associate Professor in Physiology, School of Health, University of the Sunshine Coast and Laura Pernoud, PhD Candidate in Women’s Health, School of Health, University of the Sunshine Coast

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