After the cases of hantavirus on a cruise ship and the concern that the topic caused around the world, public interest in the dangerous infection has sharply increased. How is the virus transmitted, is there a risk of mass spread, why is the Andean hantavirus different from other varieties and should people be afraid of a new pandemic… Infectious disease specialist Assoc. Prof. Dr. Atanas Mangarov speaks to FACTI.
- Assoc. Prof. Mangarov, what is the hantavirus, which has caused concern in various countries in recent days?
- The recent talk about hantaviruses is related to the infection on a cruise ship, caused by one of them, a virus that is commonly found in some parts of South America - in Chile and Argentina. Its important feature is that, unlike other hantaviruses, it can cause a disease that can be transmitted not only from animals to humans, but also from person to person. There are dozens of species of hantaviruses, and about 20 of them cause disease in humans. They are distributed throughout the world. These viruses cause two severe clinical syndromes:
1) hemorrhagic fever with renal syndrome
2) hantavirus pulmonary syndrome
Hantaviruses found in the Eastern Hemisphere - Asia and Europe, including our country, cause hemorrhagic fever with renal syndrome /HFRS/, while in the Western Hemisphere - North and South America, there are those that cause disease with renal syndrome and others that cause disease with pulmonary syndrome. The reservoir of hantaviruses are the various rodents that spread the viruses but do not get sick, and each type of hantavirus is associated with a specific type of rodent. The reservoir of the hantavirus that causes HFRS in our country and the Balkans, the so-called Dobrava-Belgrade hantavirus, is the forest mouse, and the reservoir of those that cause the same disease in Asia and Northern Europe is the field mouse. Infection occurs by ingestion of food or water contaminated with rodent excrement (urine, feces, saliva) or by inhalation of dust particles containing dried such excrement. It can also occur through bites or scratches from infected rodents. Human-to-human transmission has not been described. The only exception so far is the so-called Andean hantavirus, which occurs in Argentina and Chile. It is currently claimed to be the cause of cruise ship illnesses and causes a disease with a pulmonary syndrome.
It is important to emphasize that there is no human-to-human transmission of hantaviruses in the Eastern Hemisphere. Infection occurs exclusively from rodents in the aforementioned ways.
In the Western Hemisphere, there are hantaviruses that cause a disease that occurs with hemorrhagic fever and kidney failure, but there are also those that cause the pulmonary form of the disease. The latter was identified and proven in the early 1990s. Infection occurs in the same way, but the disease occurs as severe viral pneumonia, often leading to pulmonary edema and respiratory failure.
So far, only in some parts of Argentina and Chile, a type of hantavirus has been identified, called the Andean virus (b.r. - after the name of the habitat - the Andes), which can be transmitted from person to person by airborne droplets and contact-household routes, but this requires extremely close contact - kissing, hugging, sleeping in the same bed, living together. This is the type of virus that caused the epidemic on the cruise ship, with the infection of patient zero most likely occurring in Argentina before sailing.
- How important is it for treatment to quickly establish that a person is developing hantavirus?
- This is not so important, because there is no etiological treatment for hantavirus infection. Treatment is pathogenetic and symptomatic - in cases of hemorrhagic fever with renal syndrome and the development of acute renal failure, acute renal failure, water and electrolyte disorders and hemorrhagic syndrome are treated. In our country, there are several dozen cases per year, and with a correct diagnosis, most are successfully treated with hemodialysis and fluid therapy. In this form of hantavirus infection, the mortality rate is about 10-15%.
The pulmonary form of hantavirus infection, such as that on the cruise ship, is characteristic of the Western Hemisphere. It occurs with a picture of rapidly developing viral pneumonia, pulmonary edema and respiratory failure.
Treatment is with oxygen administration and correction of vital signs. The mortality rate is high - 30-50%. In Bulgaria, the pulmonary form of hantavirus does not occur and there is no person-to-person infection.
- Which age group is most vulnerable to hantaviruses - children, adults or middle-aged people?
- All people who are exposed to hantaviruses in the described ways can become infected, regardless of their age and physical condition. Advanced age and the presence of concomitant diseases are risk factors. In our country, people living or working in forested areas who may consume food or water contaminated with rodent excrement - urine, feces, saliva, etc. are at risk. A significant increase in cases in our country occurred in the 1960s-70s during the construction of large dams in the Rhodope Mountains. There is also a risk for people who live in abandoned premises or in places heavily infested with rodents. To get sick, a person must consume contaminated water, food, or inhale infected dust particles.
- And how do rodents themselves deal with the virus? Doesn't their immune system suffer from it?
- They are a reservoir for the virus and the animals themselves do not get sick. They simply live with the viruses and spread them. In the Balkans, including in our country, hantaviruses are spread mainly by forest mice, and in other parts of Europe and Asia - by field mice. Different types of hantaviruses have different types of rodents as reservoirs.
- What preventive measures should people take if they find themselves in an environment with a potential risk - for example, in mountainous or rural areas?
- I want to emphasize that this is a rare disease. In our country, people who walk in the forests and can consume food, berries, etc. or drink water from springs contaminated with the excrement of forest mice mostly get sick. A person sees a clean and clear spring, but does not know whether a few meters up a mouse has contaminated the water.
- Is there a possibility of vaccine prophylaxis?
- Vaccines against local types of hantaviruses, which cause hemorrhagic fever with renal syndrome, have been developed only in China and South Korea. There, they are administered to people working in risk areas and the military. Data on their effectiveness are scarce. In other parts of the world, there are no licensed vaccines against hantaviruses. The existence of many different types of hantaviruses, as well as the limited contingent to which they can be administered, is an obstacle to the creation of hantavirus vaccines. However, the high mortality rate of the various hantavirus syndromes - 10-15% for HTBS and 40-50% for pulmonary syndrome - makes them particularly dangerous infections, with the potential for use as a biological weapon. There is no way this has not attracted the attention of military laboratories.
- If we return to the case with the ship, what is the problem there?
- The problem there is with the pulmonary form of the disease and the fact that it is caused by the only hantavirus that can be transmitted from person to person by airborne droplets and contact-household routes. The people on the ship, or the so-called zero patient, most likely became infected while they were in Argentina, and not from rodents on the ship itself. They probably visited a place where there was a possibility of infection. The incubation period of hantavirus infection is between 1 and 6 weeks. All contacts on the ship will be quarantined for 42 days.
- Information has already emerged about the so-called “patient zero“. Is it a photographer who visited a landfill in Argentina to take pictures?
- That must be the case. But this case is creating excessive anxiety and too much media attention. In the current geopolitical crises, this is a good approach to divert focus from the real problems. In addition, various “authorities“ are beginning to appear, claiming that this Andy hantavirus is easily transmitted from person to person, without the need for close contact. This is not true. The story is very reminiscent of some events from the beginning of the COVID pandemic and the accompanying hysteria...
- After the COVID pandemic, society is very sensitive to any news about a virus. Are we better prepared today?
- There is no reason for something like this to be hyped to such an extent, unless something else, bigger, is being prepared in the foreseeable future. This is the so-called Overton window, in which something that at first glance seems unthinkable gradually becomes a real possibility. A process like a frog that is slowly boiled in water, the water gradually heats up and the stupid frog dies without realizing it.
- But here, does the fact that the case occurs on a cruise ship, where people are restricted in their movement, contribute to the anxiety?
- Of course. A cruise ship is a closed society, with many people in one place and limited opportunities for isolation, a kind of miniature model for tracking the spread of a specific virus in an environment resembling a modern city. If you remember, at the beginning of COVID-19 - in February 2020, the situation was the same. The first cases had appeared in China and there was a cruise ship with sick people who were from other parts of the world. The ship was traveling around without anyone wanting to accept it. Finally, it docked in Japan, in Yokohama. Looking at how things are developing, there are many similarities. I am worried about the excessively targeted attention from the WHO and the media. People have already started calling me with questions about what to do when hantavirus appears, someone in the media speaks out on the issue every day... I really hope that there will be no continuation. Political medicine is dangerous for personal and public health.