The occurrence of an unusual illness aboard the luxury cruise ship Hondius has reintroduced a little-known family of viruses to the public after some passengers developed a serious respiratory illness.
The hantavirus is a relatively rare virus that is usually transmitted from rodents to humans and can cause serious illness in the lungs, kidneys, and heart. Although most cases do not spread between humans, the suspicion of an outbreak at sea has sparked an international investigation and extensive testing of the source of the infection.
As of Tuesday, the World Health Organization (WHO) reported that seven passengers aboard the Hondius were sick or suspected of having contracted Hantavirus, including two confirmed cases and five suspected.
The WHO stressed that the risk to the general public is low, but an epidemiological investigation is ongoing to identify the source of the infection, including testing for the possibility of exposure to rodents or limited transmission between people who were in close contact.
Three of the passengers died, one British passenger was hospitalized in isolation in intensive care in Johannesburg, South Africa, and three others remain on the ship, which is currently anchored off Cape Verde.
According to reports, the dead included a 70-year-old Dutch man, his 69-year-old wife, and a German woman. The Dutch man developed symptoms on April 6 and died on April 11. His wife later died in a Johannesburg hospital on April 26, and the German woman died on the ship on May 2.
Hantaviruses are a family of viruses found mainly in rodents. They do not usually cause serious illness in the rodents themselves, but can be dangerous to humans. Each strain of hantavirus is usually associated with a specific species of rodent, and the virus is shed in the urine, feces, and saliva of the infected animal.
Humans are most often infected when tiny particles of dried rodent droppings are dispersed into the air and inhaled into the lungs. This can happen while cleaning a warehouse, cabin, attic, equipment room, storage room, kitchen, or any enclosed space where mice or rats have been.
While the main route of transmission is through the inhalation of contaminated dust, there are other ways that the virus can enter the human body.
A person can become infected by touching a contaminated surface and then touching their mouth, nose, or eyes. Infection following a bite or scratch from a rodent is possible, but is considered rarer.
Therefore, recommendations for prevention focus not only on keeping rodents away, but also on how potentially infected areas are cleaned.
When cleaning an area where contaminated dust may be, it is recommended not to dry sweep, not to vacuum normally, and not to lift dry secretions into the air. Instead, potentially infected areas should be moistened with an appropriate disinfectant and wiped carefully using gloves, while making sure the area is well-ventilated.
Most hantaviruses are not transmitted from person to person. The best-known exception is the Andean strain, which originates in South America and has previously been described as capable of being transmitted between humans in rare cases, mainly through close and prolonged contact.
Therefore, the fact that the infection showed up after the ship visited southern Argentina, it is of particular interest to infectious disease experts.
At this stage, it is not possible to determine the source of the outbreak on the ship. One possibility is that rodents boarded the ship or were in one of the storage areas.
Another possibility is that passengers were exposed to the virus before boarding the ship or during a stay at one of the destinations. A third possibility, considered much rarer, is that the virus had spread between people through close contact.
Symptoms of hantavirus infection
The incubation period of the disease varies depending on the strain. In antenatal pulmonary syndrome, symptoms usually appear two to four weeks after exposure, but can appear as early as one week after exposure.
In the early stages of infection, the disease may look like a normal viral infection: fever, chills, muscle aches, headache, severe weakness, dizziness, nausea, vomiting, diarrhea, or abdominal pain. At that stage, it is difficult to distinguish antenatal from influenza, coronavirus, other viral diseases, early pneumonia, or infections originating in the gastrointestinal tract.
Deterioration in condition may occur later. In the strains common in the Americas, hantavirus pulmonary syndrome may develop.
In hantavirus pulmonary syndrome, small blood vessels in the lungs become more permeable, allowing fluid to accumulate in the lung tissue, leading to the infected patient developing a cough, chest tightness, and worsening shortness of breath.
In some cases, a drop in blood pressure may also occur, in addition to heart failure, severe respiratory distress, and the need for ventilation.
According to the US Centers for Disease Control and Prevention, the mortality rate among those who develop respiratory symptoms of hantavirus pulmonary syndrome is about 38%. The World Health Organization notes that in some strains in the Americas, the mortality rate may reach 50%.
Other strains of hantavirus are more common in Europe and Asia, and can cause hemorrhagic syndrome with kidney damage. In this condition, the disease can begin with fever, headache, abdominal pain, and nausea, and then progress to low blood pressure, bleeding, kidney damage, and even acute kidney failure.
The severity of the disease varies greatly between strains, between regions of the world, and between different patients. Some infected people will develop a relatively mild illness, while others may rapidly deteriorate into a life-threatening condition.
Diagnosis begins with clinical suspicion. A doctor may suspect hantavirus when there is a combination of a flu-like illness or respiratory distress in a patient who experienced possible exposure to rodents, staying in rural areas, cleaning enclosed spaces, traveling to areas where the virus is known, or staying in a place where an outbreak has been reported.
Blood tests from infected individuals may show a decrease in platelets, an increase in white blood cells, impaired kidney or liver function, and sometimes signs of fluid leakage from blood vessels.
Confirmation of hantavirus diagnosis is reached with tests from a doctor.
