Jennifer Head, University of Michigan; Alexandra K. Heaney, University of California, San Diego, and Simon Camponuri, University of California, Berkeley

As the climate warms, the southwestern U.S. is increasingly experiencing weather whiplash as the region swings from drought to flooding and back again. As a result, the public is hearing more about little-known infectious diseases, such as valley fever.

In May 2024, about 20,000 people attended a music festival in Buena Vista Lake, California. In the months that followed, at least 19 developed valley fever, and eight were hospitalized from their infection. This outbreak follows a dramatic increase of more than 800% in valley fever infections in California between 2000 and 2018.

In 2023, California reported the second-highest number of valley fever cases on record, with more than 9,000 cases reported statewide. And between April 2023 and March 2024, California provisionally reported 10,593 cases – 40% more than during the same period the prior year.

The Conversation U.S. asked Jennifer Head, Simon Camponuri and Alexandra Heaney – researchers specializing in the epidemiology of valley fever – to explain what valley fever is, and what might explain its rise in recent years.

What is valley fever, and how do you get infected?

Valley fever is the common name for a disease called coccidioidomycosis, which is an infection caused by pathogenic fungi from the Coccidioides genus. The fungi are primarily found in arid soils of the southwestern United States, as well as parts of Central and South America.

When the fungus has access to moisture and nutrients, it grows long, branching fungal chains throughout the soil. When the soil dries out, these chains fragment to form fungal spores, which can be stirred up into the air when the soil is disturbed, such as by wind or digging. Airborne spores can then be inhaled and cause a respiratory infection.

Cases of valley fever are typically highest in California’s southern San Joaquin Valley and southern Arizona, but they have been increasing outside of these regions. Between 2000 and 2018, the incidence of valley fever cases increased fifteenfold in the northern San Joaquin Valley and eightfold along the Southern California coast. And between 2014 and 2018, incidence increased by more than eightfold along the central coast.

Because of these trends and the virulence of the pathogen that causes valley fever, it is listed as a priority pathogen by the World Health Organization. Historically, fungal infections have received very little attention and resources. By creating this list, the WHO is hoping to galvanize action surrounding listed pathogens, including getting more resources for research as well as the development of new treatments.

What are the symptoms, and what should people be looking for?

After inhaling fungal spores from the environment, Coccidioides initially infects the lungs, causing symptoms like mild to severe cough, fever, difficulty breathing, chest pain and tiredness. Valley fever symptoms can resemble other common respiratory infections, so it’s important for people to get checked by a doctor if they’ve experienced prolonged symptoms, particularly if they have been given antibiotics that they are not responding to.

In California and Arizona, an estimated one-third of community-acquired pneumonia cases – or pneumonia acquired outside of the hospital – are caused by valley fever. However, only a fraction of community-acquired pneumonia cases get tested for it, so it’s likely the number of valley fever cases is significantly higher. Among diagnosed cases, half experienced symptoms for two months or more before being diagnosed.

In 5% to 10% of cases, the fungus can spread from the lungs to other parts of the body, such as the central nervous system, liver and bones, causing meningitis or arthritis-like symptoms. These cases can be severe and possibly fatal.

Antifungal treatment is available, and early diagnosis and treatment is critical for better outcomes.

What time of year should you be most concerned?

Valley fever cases can occur year-round, but in California, cases reported via surveillance systems tend to increase starting in August and September, peak in November and return to background levels in January and February.

Researchers believe that patients are likely exposed to the fungus in the summer and early fall months, typically one to three months prior to their diagnosis. This delay accounts for time between when patients are exposed, develop symptoms and are diagnosed with the disease. While cases peak in the fall on average, seasonal strength and timing varies regionally.

Our research shows that this seasonal surge in the fall is especially strong following wetter winters and that alternation between dry and wet conditions is associated with increased incidence in fall months.

Valley fever cases in California nearly doubled following wet winters that occurred one and two years after the 2007-2009 and 2012-2015 droughts.

In 2023, California experienced a similar transition, with an extreme drought occurring between 2020-2022 followed by heavy precipitation in the winter of 2022-2023.

This transition was followed by a near-record spike in cases in 2023. The state experienced another wet winter during the 2023-2024 wet season, furthering concern about continued high risk for valley fever in 2024.

Our research team recently developed a model to forecast valley fever cases that will occur between April 2024 and March 2025 in California. We forecast that the state is likely to see another spike in cases during the fall and winter of 2024, on par with the spike in 2023.

During high-risk periods, clinicians should consider valley fever as a potential diagnosis. This is especially true when evaluating a patient presenting with valley fever symptoms or a respiratory illness who lives in, works in or traveled to an endemic or emerging region.

We are currently working to characterize seasonal disease patterns in Arizona as well, which are different from California’s. This is likely because Arizona has two rainy seasons.

Are some people at greater risk than others?

Those who spend time or work outdoors in areas where valley fever is common, especially where they may be exposed to dirt and dust, are more likely to get it.

While healthy people are still at risk of infection, certain factors can increase the likelihood of developing severe disease from valley fever. These include being an adult 60 years or older, having diabetes, HIV or another condition that weakens the immune system, or being pregnant. People who are Black or Filipino also have been noted to have a higher risk of severe disease, which may relate to more exposure to the fungal spores, underlying health conditions, inequities in accessing care or other possible predispositions.

How can you protect yourself from getting valley fever?

People who live and work in the regions where the fungus is found should avoid exposure to dust as much as possible. When it is windy outside and the air is dusty, stay indoors and keep windows and doors closed.

When driving through a dusty area, limit vehicle speed, keep car windows closed and recirculate the air, if possible. When working outdoors, use dust suppression techniques, including wetting soil before digging to prevent stirring up dust, and installing fencing, windbreaks and vegetation where possible.

For those who must directly stir up soil or be in dusty conditions, such as while doing construction or gardening work, consider using an N95 mask to limit dust inhalation.

Jennifer Head, Assistant Professor of Epidemiology, University of Michigan; Alexandra K. Heaney, Assistant Professor in Climate and Health Epidemiology , University of California, San Diego, and Simon Camponuri, PhD Candidate in Environmental Health Sciences, University of California, Berkeley

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

Claire Therese Hemingway, University of Tennessee

Just like people confronted with a sea of options at the grocery store, bees foraging in meadows encounter many different flowers at once. They must decide which ones to visit for food, but it isn’t always a straightforward choice.

Flowers offer two types of food: nectar and pollen, which can vary in important ways. Nectar, for instance, can fluctuate in concentration, volume, refill rate and accessibility. It also contains secondary metabolites, such as caffeine and nicotine, which can be either disagreeable or appealing, depending on how much is present. Similarly, pollen contains proteins and lipids, which affect nutritional quality.

When confronted with these choices, you’d think bees would always pick the flowers with the most accessible, highest-quality nectar and pollen. But they don’t. Instead, just like human grocery shoppers, their decisions about which flowers to visit depend on their recent experience with similar flowers and what other flowers are available.

I find these behaviors fascinating. My research looks at how animals make daily choices – especially when looking for food. It turns out that bees and other pollinators make the same kinds of irrational “shopping” decisions humans make.

Predictably irrational

Humans are sometimes illogical. For instance, someone who wins $5 on a scratch ticket immediately after winning $1 on one will be thrilled – whereas that same person winning $5 on a ticket might be disappointed if they’re coming off a $10 win. Even though the outcome is the same, perception changes depending on what came before.

Perceptions are also at play when people assess product labels. For instance, a person may expect an expensive bottle of wine with a fancy French label to be better than a cheap, generic-looking one. But if there’s a mismatch between how good something is and how good someone expects it to be, they may feel disproportionately disappointed or delighted.

Humans are also very sensitive to the context of their choice. For example, people are more likely to pay a higher price for a television when a smaller, more expensive one is also available.

These irrational behaviors are so predictable, companies have devised clever ways to exploit these tendencies when pricing and packaging goods, creating commercials, stocking shelves, and designing websites and apps. Even outside of a consumer setting, these behaviors are so common that they influence how politicians design public policy and attempt to influence voting behavior.

Like minds

Research shows bumblebees and humans share many of these behaviors. A 2005 study found bees evaluate the quality of nectar relative to their most recent feeding experience: Bees trained to visit a feeder with medium-quality nectar accepted it readily, whereas bees trained to visit a feeder with high-quality nectar often rejected medium-quality nectar.

My team and I wanted to explore whether floral traits such as scents, colors and patterns might serve as product labels for bees. In the lab, we trained groups of bees to associate certain artificial flower colors with high-quality “nectar” – actually a sugar solution we could manipulate.

For example, we trained one group to associate blue flowers with high-quality nectar. We then offered that group medium-quality nectar in either blue or yellow flowers.

We found the bees were more willing to accept the medium-quality nectar from yellow flowers than they were from blue. Their expectations mattered.

In another recent experiment, we gave bumblebees a choice between two equally attractive flowers – one high in sugar concentration but slower to refill and one quick to refill but containing less sugar. We measured their preference between the two, which was similar.

We then expanded the choice by including a third flower that was even lower in sugar concentration or even slower to refill. We found that the presence of the new low-reward flower made the intermediate one appear relatively better.

These results are intriguing and suggest, for both bees and other animals, available choices may guide foraging decisions.

Potential uses

Understanding these behaviors in bumblebees and other pollinators may have important consequences for people. Honeybees and bumblebees are used commercially to support billions of dollars of crop production annually.

If bees visit certain flowers more in the presence of other flowers, farmers could use this tendency strategically. Just as stores stock shelves to present unattractive options alongside attractive ones, farmers could plant certain flower species in or near crop plants to increase visitation to the target crops.

Claire Therese HemingwayUniversity of Tennessee

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

Rodney E. Rohde, Texas State University and Charles Rupprecht, Auburn University

Rabies is a deadly disease. Without vaccination, a rabies infection is nearly 100% fatal once someone develops symptoms. Texas has experienced two rabies epidemics in animals since 1988: one involving coyotes and dogs in south Texas, and the other involving gray foxes in west central Texas. Affecting 74 counties, these outbreaks led to thousands of people who could have been exposed, two human deaths and countless animal lives lost.

In 1994, Gov. Ann Richards declared rabies a state health emergency. The Texas Department of State Health Services responded by launching the Oral Rabies Vaccination Program to control the spread of these wildlife rabies outbreaks.

Since 1995, the program has distributed over 53 million doses of rabies vaccine over 758,100 square miles (nearly 2 million square kilometers) in Texas by hand or aircraft. Rabies cases in dogs and coyotes went from 141 to 0 by 2005, and rabies cases in foxes went from 101 to 0 by 2014. By 2004, one canine rabies variant was effectively eliminated from Texas, and another variant was substantially controlled.

We are researchers who began studying wildlife rabies and oral vaccination in the 1980s. From providing a proof of concept in using oral vaccines in raccoons to being among the first to use new rabies vaccines in the 1990s, we were on the ground floor of efforts to contain this deadly virus.

Decades of vaccine research led to one of the most successful public health projects in Texas. And we’re hopeful it could provide a road map for the use of mass wildlife vaccination to prevent future outbreaks.

Developing the oral rabies vaccine

The Texas Oral Rabies Vaccination Program benefited greatly from the work of multiple researchers over prior decades.

The mid-20th century saw several major developments in rabies control. With the failure of efforts to poison or trap infected animals, virologist and veterinarian George Baer at the U.S. Centers for Disease Control and Prevention recognized the need for a different strategy to prevent and control wildlife rabies. His and his colleagues’ work in the 1960s led to the concept of oral rabies vaccination. While orally vaccinating wildlife would help combat infection at its source, it was previously thought to be logistically unfeasible given the large range of target animals.

By the late 1970s, European researchers began the first field trials to orally vaccinate foxes against rabies. Small plastic containers were filled with vaccines and placed into baits, such as chicken heads. Over 50,000 of these vaccine-laden baits were distributed over four years in fox habitats in forests and fields.

Researchers in Canada also began similar field trials in Ontario. During the 1980s, an average of 235 rabid foxes per year were reported in the area. Baits containing oral rabies vaccine were dropped annually from 1989 to 1995 and successfully eliminated the fox variant of rabies from the whole area.

Recombinant oral rabies vaccine

The first generation of these vaccines used live viruses modified in an attempt to not cause severe disease. Although effective and generally safe, the original rabies vaccines had to be kept in cool temperatures and had the rare risk of causing rabies in animals.

In the early 1980s, scientists developed recombinant rabies vaccines, which use a separate virus to express the genes of the rabies virus. A collaboration between a nonprofit institute, the U.S. government, and the pharmaceutical industry led to the development of a recombinant viral vaccine that produced a rapid immune response against rabies without the possibility of causing rabies.

In 1984, preliminary work in laboratory animals showed the promise of using an oral form of the recombinant vaccine to vaccinate animals. However, the concept of using genetically modified organisms was in its infancy among both scientists and the general public. While the vaccine was safe and effective in captive raccoons and foxes, major questions loomed over how it might affect other species once released into the environment.

After years of work improving the vaccine’s design and testing its safety in several nonhuman species, the first European trial was held on a military base in Belgium. With data supporting it could safely and effectively control wildlife in Luxembourg and France, the vaccine was licensed to control fox rabies in 1995.

In the U.S., similar studies of the oral recombinant rabies vaccine were conducted. The first trial began in 1990 at Parramore Island off the Virginia coast, and a year of intensive monitoring found no significant adverse effects on the environment or any wildlife species. A second yearlong study on the mainland near Williamsport, Pennsylvania, had similarly positive results.

After the vaccine was successfully used to control raccoon rabies in tests in several other East Coast states, it was approved for use on raccoons in 1997.

In 1998, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service and the U.S. Fish and Wildlife Service received funding to expand existing oral wildlife vaccination projects to states of strategic importance, to prevent the spread of specific rabies viruses, and to coordinate interstate projects.

Results in Texas

In Texas, the oral recombinant vaccine is now primarily distributed by hand and by approximately 75 separate helicopter flights annually.

The Texas Department of State Health Services rabies laboratory worked alongside the CDC to create the Regional Rabies Virus Reference Typing Laboratory. One of us was recruited to both distribute the vaccine in the field and to develop molecular typing tools to discriminate between different types of rabies virus variants in the lab. These techniques allowed us to identify where different rabies virus variants were emerging at any given moment.

Our lab was also the first in the nation outside of the CDC to assist other U.S. states and countries in testing their specimens for rabies virus variants. These techniques helped researchers monitor where the rabies epizootic was ongoing or retreating due to wildlife vaccination and new forms of spread.

With the constant threat of emerging and reemerging infectious diseases like COVID-19 and influenza, the prospect of mass vaccination of wild animals may be one way to address future pandemics. Though there is much work ahead of us, we have hope that we may one day have the option of using mass wildlife vaccination to reduce or eliminate infectious diseases like rabies.

Rodney E. RohdeTexas State University and Charles Rupprecht, Affiliate Professor of Veterinary Medicine, Auburn University

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