Extreme climate events are becoming more frequent, longer-lasting, and more intense, allowing viruses that were once confined to specific regions to spread to new areas, threatening people who haven’t developed immunity.
This outbreak on the cruise ship has raised concerns due to its unusual transmission path. Experts believe this is closely related to extreme weather, habitat destruction, and rising temperatures.
National Center for Infectious Diseases, Fudan University Affiliated Huashan Hospital Infectious Diseases Director Zhang Wenhong, and others pointed out that the host animals of the hantavirus, rodents, have expanded their habitats, breaking geographical boundaries, allowing the Andes virus, previously confined to South America, to spread to new regions and break out in non-traditional environments like polar cruise ships.
Not coincidentally, a study conducted by researchers from Australia, the UK, and the US found that the Antarctic is likely transitioning from a “buffer” to an “amplifier” of global warming, especially since 2015.
Huashan Hospital’s Infectious Diseases Department wrote on their official WeChat account that from an epidemiological perspective, the focus of this event is on a traveler who may have been exposed to the natural source of the virus in South America, then entered the relatively closed environment of the polar cruise ship, where people live together for extended periods, leading to limited secondary transmission and contact tracing across multiple countries.
Recently, Argentina’s climate has been characterized by high temperatures and uneven precipitation, with heavy rainfall in some areas and drought in agricultural regions.
According to the National Climate Center, the equatorial central Pacific will enter an El Niño state in May, with a moderate to strong El Niño event forming in the summer and autumn, peaking in the autumn and winter, and the probability of a strong El Niño event is increasing.
Research based on the World Health Organization’s global influenza plan database found that during El Niño events, large-scale influenza outbreaks increase, and abnormal temperature fluctuations in winter will lead to more severe influenza epidemics the following year.
Thanks to the melting of glaciers and permafrost, ancient pathogens are re-emerging. As early as 2014, a giant virus with a diameter of 1.5 micrometers was discovered in Siberia. Later, in a melting ice lake in the Canadian Arctic Circle, scientists discovered another giant virus.
Global warming is extending the transmission period of infectious diseases that were previously limited to summer, and diseases originating from the tropics, such as gastrointestinal infections, vector-borne diseases, and parasitic diseases, are gradually spreading to temperate and even cold regions.
In 2021, Liu Qiyong, a researcher at the Chinese Center for Disease Control and Prevention, published a paper titled “The Impact of Climate Change on Vector-Borne Diseases in China and Countermeasures,” which pointed out that vector-borne diseases are the most sensitive to climate change, and the spatial distribution, reproduction, and amplification of pathogens in vectors are all affected by climate factors.
Wei Ke, deputy director of the Seasonal Forecasting System Research Center at the Chinese Academy of Sciences’ Institute of Atmospheric Physics, previously said in an interview with Jiemian News that as temperatures rise, some tropical vector-borne diseases will spread to mid-to-high latitudes, such as dengue fever, and invasive species may have severe impacts.
In an unstable climate environment, human vulnerability to infectious diseases is becoming increasingly apparent. A study published in Nature Climate Change in August 2022 found that among 375 known human pathogenic diseases, 218 were exacerbated by climate-related disasters. The study listed the pathways by which climate hazards increase disease transmission: floods increase the transmission of hepatitis, rising temperatures prolong the lifespan of mosquitoes carrying malaria, and droughts cause rodents infected with hantavirus to enter human communities in search of food.
In November 2023, the US federal government’s Fourth National Climate Assessment report showed that climate change poses health risks, including increased transmission of certain infectious diseases, such as West Nile virus, dengue fever, Lyme disease, Rocky Mountain spotted fever, rabies, and valley fever, which are all “climate-sensitive” diseases.
The report concluded that as the climate warms, the fungal disease “valley fever” will gradually move north in the US Southwest. If climate change continues unabated, the incidence of this disease will increase by 220% by the end of the century.
The World Health Organization and health departments of several countries have confirmed that the hantavirus involved in this outbreak is the Andes virus, which is the only known hantavirus that can be transmitted between humans.
The majority of passengers on the cruise ship were elderly people with weaker immune systems, further fueling negative speculation and anxiety.
WHO Director-General Tedros Adhanom Ghebreyesus said at a press conference that given the long incubation period of the Andes virus, which can last up to six weeks, future case data will show small-scale outbreaks. He emphasized that although this is a serious outbreak, the WHO assesses that the risk to public health remains relatively low. On May 12, he further stated that there is no indication that the hantavirus is experiencing a larger-scale outbreak.
