Health officials are issuing warnings about a significant increase in seasonal fevers, including dengue fever, influenza (flu), and various water-borne illnesses. Several factors are contributing to this surge, creating a challenging situation for healthcare systems and the public.
Dengue Fever on the Rise
Dengue fever, a mosquito-borne viral disease, is exhibiting a concerning upward trend. The World Health Organization (WHO) reports a dramatic increase in dengue incidence globally, with reported cases soaring from 505,430 in 2000 to 14.6 million in 2024. In 2024, more dengue cases were recorded than ever before in a 12-month period, affecting over 100 countries across all continents. From January to July 2025, over 4 million cases and over 3,000 deaths have been reported to WHO from 97 countries. Several cities, including Mumbai, Kolkata, and Delhi NCR, are experiencing a spike in dengue cases. In Delhi NCR, 121 cases were reported in August, and numbers are expected to increase.
Several factors contribute to the increased risk of dengue spread. These include the changing distribution of mosquitoes that transmit the disease, climate change leading to higher temperatures and humidity, and limitations in disease surveillance and reporting. Warmer, wetter weather conditions have expanded the habitats suitable for mosquitos, accelerating their life cycle and viral replication rates. Unplanned urbanization and increased international travel also play a role in spreading the virus.
Influenza (Flu) Cases Surging
Alongside dengue, cases of influenza are also on the rise. In February 2025, flu rates in the U.S. spiked to the highest levels seen in at least 15 years, surpassing COVID-19 infections and hospitalizations for the first time since the pandemic began. The Centers for Disease Control and Prevention (CDC) has classified this flu season as having "high" severity across the U.S.. Some hospitals are reporting a sharp rise in "long flu" cases, where symptoms persist for over four weeks, affecting both children and adults. These prolonged cases are often linked to influenza A subtypes such as H3N2 and H1N1 (swine flu). Lower vaccination rates have contributed to the surge in flu cases, leaving a greater portion of the population unprotected.
Water-Borne Illnesses Increasing
The increase in seasonal fevers is accompanied by a rise in water-borne diseases. These illnesses, caused by pathogens spread through water, affect over 7 million people in the U.S. annually, costing the healthcare system over $3 billion. Changes in weather and climate patterns, including heavy rainfall and flooding, can lead to the dissemination of raw sewage, harmful chemicals, and pathogens, increasing the risk of water-borne illnesses. Rural communities that rely on private wells are particularly vulnerable to contamination during floods. Outbreaks of Legionnaires' disease, a severe type of pneumonia caused by Legionella bacteria in water systems, have also been reported, with cases rising significantly. A recent outbreak in New York City sickened over 100 people and resulted in five deaths.
Public Health Recommendations
To combat the spread of these seasonal illnesses, health officials recommend several preventive measures:
The confluence of rising dengue, flu, and water-borne illness cases presents a significant challenge to public health. By taking proactive preventive measures and seeking timely medical care, individuals can help protect themselves and their communities from these seasonal threats.
