The recent outbreak of Hantavirus infections aboard the Dutch expedition cruise ship MV Hondius, which had been sailing from Ushuaia through the South Atlantic toward the Canary Islands, combined with the painful memory of the COVID pandemic, has raised public awareness and fear to levels probably beyond the boundary of reality. Below are a few salient facts about the virus and its effects on humans.
Hantaviruses form a large family of rodent-borne viruses distributed across much of the world. Some cause severe lung disease, while others primarily attack the kidneys. Although infections remain relatively rare, hantaviruses are important because of their high mortality rates and the difficulty of early diagnosis.
Hantaviruses belong to a group of RNA viruses in the family Hantaviridae. Unlike influenza or COVID-19, hantaviruses are not primarily spread from person to person. Instead, each type of hantavirus is usually associated with a particular rodent species that serves as its natural host.
The rodents themselves generally do not become ill. They carry the virus chronically and shed it in urine, droppings, and saliva. Humans become infected mainly by inhaling tiny airborne particles contaminated with these materials. The name “hantavirus” comes from the Hantan River region of South Korea, where one of the earliest recognized forms of the disease was identified during the Korean War. Hantaviruses cause two major clinical syndromes.
1. Hantavirus Pulmonary Syndrome (HPS)
This form occurs mainly in the Americas and is the best-known type in the United States. The most important American hantaviruses include:
- Sin Nombre virus – the principal cause of HPS in the United States and Canada
- Andes virus – found mainly in Argentina and Chile
- Black Creek Canal virus
- Bayou virus
HPS begins like a flu-like illness but can rapidly progress to catastrophic lung failure.
2. Hemorrhagic Fever with Renal Syndrome (HFRS)
This form predominates in Europe and Asia. It primarily damages the kidneys rather than the lungs. Important Eurasian hantaviruses include:
- Hantaan virus
- Seoul virus
- Puumala virus
- Dobrava-Belgrade virus
The severity of HFRS varies considerably. Puumala virus infections in Scandinavia may be relatively mild, while Hantaan virus infections can be severe and life-threatening.
Hantaviruses exist on nearly every continent where rodent hosts live. In the United States, cases cluster most heavily in the Southwest, especially New Mexico, Arizona, Colorado, and Utah. Cases also occur in Texas and California.
The Clinical Course of HPS
The incubation period is usually one to six weeks after exposure. Initial symptoms are nonspecific and resemble many viral illnesses. Initial symptoms are nonspecific and resemble many viral illnesses:
- Nausea and Vomiting
- Fever
- Severe muscle aches
- Fatigue
- Headache
Nausea and Vomiting - Abdominal pain
Because these symptoms are so common, early hantavirus infection is often misdiagnosed as influenza or another viral syndrome. In HPS, the illness may suddenly worsen after several days. Patients can develop:
- Cough
- Shortness of breath
- Rapid breathing
- Falling blood pressure
- Fluid accumulation in the lungs
The deterioration can be alarmingly rapid. Some patients require intensive care within hours of the onset of respiratory symptoms. Mortality for HPS in North America is roughly 30–40%, even with modern intensive care.
The Clinical Course of HFRS
In the Eurasian form, kidney injury predominates. Patients may develop:
- Low blood pressure
- Bleeding abnormalities
- Reduced urine output
- Acute kidney failure
Many survivors recover completely, though recovery may take weeks or months. Diagnosis can be difficult because the early symptoms mimic common infections. Rapid recognition is important because patients can deteriorate suddenly. Diagnosis is made by the following:
- History of rodent exposure
- Blood tests detecting antibodies or viral RNA
- Chest imaging in pulmonary disease
- Laboratory evidence of kidney injury in HFRS
There is no universally effective antiviral cure for hantavirus infection. Treatment is mainly supportive and often requires intensive care. For severe HPS, patients may need:
- Oxygen
- Mechanical ventilation
- Blood pressure support
- Extracorporeal membrane oxygenation in extreme cases
The outbreak that occurred on the cruise ship MV Hondius has so far resulted in 8 to 11 cases of hantavirus infection, including three deaths. The virus involved appears to be the Andes virus, the one hantavirus subtype known to permit limited human-to-human transmission.
The illness reportedly began with fever, gastrointestinal symptoms, muscle aches, and fatigue, then in several patients progressed rapidly to severe pneumonia, respiratory distress, and shock – the classic picture of hantavirus pulmonary syndrome.
Where did the virus come from? At the moment, public-health authorities do not think the outbreak originated from rodents living aboard the ship. The current leading hypothesis from the European Centre for Disease Prevention and Control is that at least one passenger was infected before boarding, probably during travel in parts of Argentina or Chile where the Andes virus is endemic. Experts think that rodents on board the ship were not responsible for the outbreak. Nevertheless, investigators are almost certainly inspecting the ship for rodent contamination anyway.
The current consensus appears to be that the outbreak probably began with a passenger infected on land in South America, and that some secondary onboard transmission may have occurred. A hidden rodent infestation aboard the ship is considered possible in theory, but is not the leading explanation at present.
