Extreme Weather Events Spike Storm-Related Infections

In the aftermath of a hurricane, the risk for waterborne and mosquito-borne infections increases. Storm-driven flooding often contaminates environmental, recreational, and drinking water sources, raising the risk of waterborne infectious disease transmission. Damaged septic systems and boat septic holding tanks release waste and fuel during hurricanes, creating brackish water where bacteria thrive. Large pools of warm, standing water serve as ideal mosquito breeding grounds. Consequently, the U.S. Department of Health and Human Services advises hospitals and other healthcare providers to prepare for a surge in patients who fall ill post-storm, and increasing extreme weather events are spiking those surges.¹

Waves of Waterborne Infectious Diseases

Among the most significant hurricane-related waterborne threats are gastrointestinal illnesses such as hepatitis A or norovirus from contaminated water and illnesses from water-dwelling bacteria.

Vibrio vulnificus

According to the Florida Department of Health, infections from Vibrio vulnificus, a Gram-negative, motile, curved rod-shaped pathogenic bacteria in Vibrio, are typically rare. However, hurricane-related storm surges that mix salt water with fresh water create ideal conditions for bacterial growth in hurricane-hit areas.²

Individuals who are immunocompromised are at increased risk for Vibrio vulnificus infection, which can lead to necrotizing fasciitis. Many patients require intensive care or limb amputations, and about one in five people with Vibrio vulnificus infection die, sometimes within one to two days of becoming ill, according to the U.S. Centers for Disease Control and Prevention^.3

As of October 15, 2024, the Florida Department of Health confirmed 77 cases of Vibrio vulnificus infection and 15 deaths due to Vibrio vulnificus in 2024, far surpassing the 2023 totals of 46 cases and 11 deaths.² 

Escherichia coli

Many strains of Escherichia coli (E. coli) cause mild infections, but some strains, such as Shiga toxin-producing E. coli (STEC), cause diarrhea, which can be bloody and may lead to serious illness, including kidney damage.⁴

A study published in Eurosurveillance investigating an outbreak of Shiga toxin-producing Escherichia coli in the UK identified contaminated lettuce as the most likely source of the infection, concluding that heavy rainfall and flooding may have carried STEC from animal feces to lettuce crops—conditions like those caused by hurricanes.⁵

A multi-year study in Emerging Infectious Diseases of patients exposed to tropical storm-related rainfall in the U.S. noted a 48% (95% CI 27%–69%) increase in STEC infections one week after storms.⁶

The Florida Climate Center reported that a larger proportion of storms have reached major hurricane (Category 3-5) strength in recent years, and coastal flooding from storm surge is expected to increase regardless of changes in storm intensity due to future sea level rise.⁷ As storm strength and coastal flooding increase in Florida, so do rates of Shiga toxin-producing Escherichia coli (STEC) infections: the Florida Department of Health reported that the STEC infection rate per 100,000 residents rose from 0.2 in 2006 to 5.0 in 2023.⁸

Legionnaires’ Disease

Legionnaires’ disease, a type of pneumonia contracted by inhaling contaminated water droplets or dust that contains Legionella bacteria, causes symptoms including cough, fever, headache, muscle aches, and shortness of breath. Additional symptoms, such as confusion, diarrhea, or nausea, can also occur. Although most healthy people exposed to Legionella do not become ill, those at increased risk include:

• Current or former smokers;
• People aged 50 years or older; and
• People with specific health issues or conditions: Cancer, chronic lung disease, diabetes, kidney/liver failure, and weak immune system.⁹

During hurricane season, the risk of Legionnaires’ disease can increase due to disrupted water systems, stagnant water, and damaged cooling towers.¹⁰ The multi-year study of patients exposed to tropical storm-related rainfall in the US found a 42% (95% CI 22%–62%) increase in Legionnaires’ disease two weeks after storms.⁶

 In Florida, most cases of Legionnaires’ disease occur from August to October, coinciding with the Atlantic hurricane season, which runs from June 1 to November 30. Since 2002, reported cases of Legionnaires’ disease in Florida have risen by over 650%.¹¹ In 2020, Florida accounted for nearly 60% of Legionnaires’ disease outbreaks nationally.

Cryptosporidiosis

Fecal-oral transmission of the parasite Cryptosporidium results in cryptosporidiosis.¹² Although some individuals with cryptosporidiosis exhibit no symptoms, mild to severe watery diarrhea is the most common symptom. Other symptoms include stomach cramps/pain, dehydration, nausea, vomiting, fever, and weight loss.

While the small intestine is the site most commonly affected, cryptosporidiosis can also impact other digestive or respiratory tract areas. The infection can be severe and persistent in immunocompromised individuals.

A review of 14 studies providing epidemiological evidence of the influence of weather and climate on cryptosporidiosis worldwide showed that its incidence is highly sensitive to climatic conditions, especially temperature, rainfall, and relative humidity.¹³ During the past two decades, cryptosporidiosis has become recognized as one of the most common causes of waterborne disease (recreational water and drinking water) in humans in the U.S, with a multi-year nationwide study showing a 52% (95% CI 42%–62%) increase in cryptosporidiosis cases during storm weeks.⁶

Mosquito-Borne Viruses Boom

In addition to causing considerable public nuisance and discomfort, mosquitoes are vectors for arboviral diseases in the U.S.¹⁴ The Centers for Disease Control (CDC) warns that the types of mosquitoes that spread viruses may increase two weeks after a hurricane. Consequently, there is an increased risk for infections in areas with ongoing transmission of viruses like dengue and West Nile. Pregnant women, older adults, and infants are particularly vulnerable to mosquito-borne illnesses.

Dengue Fever

Dengue fever is a mosquito-borne disease caused by four related dengue viruses (DEN-1, DEN-2, DEN-3, DEN-4) related to the viruses that cause West Nile infection and yellow fever. Although Dengue fever can be painful and debilitating, it is rarely fatal. Symptoms include sudden onset of fever, severe headache, eye pain, muscle and joint pain (giving the disease the nickname “breakbone fever”), and bleeding. Gastrointestinal symptoms such as vomiting and diarrhea may also be present. Dengue hemorrhagic fever is a rare but more severe form of dengue infection that can be fatal if not recognized and treated.¹⁵

Earlier this year, the World Health Organization reported that the U.S. was experiencing three times more dengue fever cases than at the same point in 2023.

In Florida, there had not been a report of locally acquired dengue since 1934 until 2009. However, according to the state’s Department of Health, there have been at least 50 cases of locally acquired dengue fever in Florida this year, with new cases continuing to emerge.

North Carolina has also seen a spike in dengue fever cases due to the devastating effects of Hurricane Helene.¹⁶

West Nile Virus

West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States. Fortunately, most people infected with WNV are asymptomatic. However, about 20% of infected individuals develop symptoms, which typically include fever, headache, body aches, vomiting, diarrhea, or rash. About one in 150 individuals with WNV infection develop a serious, sometimes fatal, illness.

Of all WNV cases reported to the CDC from 1999 to 2023, 40% occurred among people aged 60 or older.¹⁷ Last year, the virus was linked to 182 deaths. So far, in 2024, there have been 289 confirmed cases of West Nile virus in the U.S., and the CDC warns the virus has spread to 33 states.

Fighting the Storm

The combination of increasing climate change-driven hurricane activity, an aging population, and deteriorating drinking and wastewater treatment systems is creating a growing storm of public health challenges.⁶ Enhanced medical research efforts, increased clinician and community awareness, and expanded climate change action are needed to combat the ever-increasing burden of hurricane-related infectious diseases.

READINGS AND RESOURCES

1. Major Hurricanes: Potential Health and Medical Implications. U.S. Department of Health and Human Services Administration for Strategic Preparedness and Response Technical Resources Assistance Center, and Information Exchange. Updated March 2022. Accessed October 21, 2024. https://files.asprtracie.hhs.gov/documents/asprtracie-major-hurricanes-potential-considerations-working-draft.pdf
2. Vibrio vulnificus. Florida Department of Health. Accessed October 20, 2024. https://www.floridahealth.gov/diseases-and-conditions/vibrio-infections/vibrio-vulnificus/index.html
3. About Necrotizing Fasciitis. U.S. Centers for Disease Control and Protection. Accessed October 20, 2024. https://www.cdc.gov/group-a-strep/about/necrotizing-fasciitis.html
4.  E. coli Infection. Cleveland Clinic. Accessed October 20, 2024. https://my.clevelandclinic.org/health/diseases/16638-e-coli-infection
5. Cunningham N, et al. An outbreak of Shiga toxin-producing Escherichia coli (STEC) O157:H7 associated with contaminated lettuce and the cascading risks from climate change, the United Kingdom, August to September 2022. Euro Surveill. 2024;29(36):pii=2400161. doi.org/10.2807/1560-7917.ES.2024.29.36.2400161
6. Lynch V, et al. Waterborne Infectious Diseases Associated with Exposure to Tropical Cyclonic Storms, United States, 1996–2018. Emerg Infect Dis. 2023 Aug;29(8):1548–1558. doi:10.3201/eid2908.221906
7. Hurricanes. Florida Climate Center. Accessed October 20, 2024. https://climatecenter.fsu.edu/topics/hurricanes
8. Shiga Toxin-Producing Escherichia coli (STEC) Infection. Florida Department of Health. Accessed October 20, 2024. https://www.flhealthcharts.gov/ChartsDashboards/rdPage.aspx?rdReport=NonVitalIndNoGrp.Dataviewer&cid=8616
9. How Legionella Spreads. U.S. Centers for Disease Control and Protection. January 29, 2024. Accessed October 20, 2024. https://www.cdc.gov/legionella/causes/index.html#cdc_causes_risk-risk-factors
10. The Perfect Storm: Hurricanes and Legionnaires’ Disease. IWC Innovations. July 6, 2023. Accessed October 20, 2024. https://www.iwcinnovations.com/blog/the-perfect-storm-understanding-the-relationship-between-hurricanes-and-legionnaires-disease#:~:text=Stagnant%20Water%3A%20After%20a%20hurricane,infection%20by%20contaminated%20aerosolized%20droplets.
11. Legionnaires’ Disease on Rise in Fla.: Are Property Owners Aware of Dangers to Their Guests? Law.com. September 3, 2024. Accessed October 20, 2024. https://www.law.com/dailybusinessreview/2024/09/03/legionnaires-disease-on-rise-in-fla-are-property-owners-aware-of-dangers-to-their-guests/?slreturn=20241031-11307
12. About Cryptosporidiosis. U.S. Centers for Disease Control and Protection. June 5, 2024. Accessed October 20, 2024. https://www.cdc.gov/cryptosporidium/about/index.html#:~:text=Cryptosporidiosis%20is%20a%20disease%20that,been%20contaminated%20with%20infected%20poop.
13. Ikiroma I, et al. Influence of weather and climate on cryptosporidiosis—A review. Zoonoses Public Health. 2021; 68: 285–298. https://doi.org/10.1111/zph.12785
14. Best Practices for Integrated Mosquito Management. The American Mosquito Control Association. November 2021. Accessed October 20, 2024. https://www.mosquito.org/assets/pdf/hr_november_2021_amca_bmp_ma/
15.  Dengue Fever. U.S. Centers for Disease Control and Protection. July 3, 2024. Accessed October 20, 2924. https://www.floridahealth.gov/diseases-and-conditions/dengue/
16. Infections, sewage and mosquito-borne illness outlast hurricanes. USA Today. October 15, 2024. Accessed October 20, 204. https://www.usatoday.com/story/news/health/2024/10/15/hurricane-helene-milton-infection-chronic-disease/75613124007/
17. Historic Data (1999-2023). U.S. Centers for Disease Control and Protection. June 18, 2024. Accessed October 20, 2024. https://www.cdc.gov/west-nile-virus/data-maps/historic-data.html