Hantaviruses have been present in the population for many years, and only one of them, the Andes hantavirus currently circulating, is transmitted from person to person. However, its transmissibility rate is low, as close contact with an infected person is required for transmission.
Even so, vigilance and caution are necessary given the emergence of this virus, which has already caused three deaths. There is no specific treatment or vaccine for this disease, and its mortality rate is high, at 50%.
What are hantaviruses?
All hantaviruses are related to rodents, particularly certain species of rats and mice. Credit: R.S.
Dr. Narces Alcocer Ayuso, an epidemiology specialist, explains that hantaviruses are a family of viruses that have been present in Mexico for quite some time, practically since their discovery in the 1950s, when the agent was first isolated in Korea.
He specifies that all hantaviruses are related to rodents, particularly certain species of rats and mice, animals that move alongside the human population, given that one of their food sources is through human activities.
As Dr. Narces Alcocer explained:
“It is always a risk to have rats or mice nearby, because hantaviruses are viruses that they carry naturally, just as humans are also natural carriers of many viruses. Hantaviruses are not dangerous for rodents, but they can transmit them to humans.
Therefore, it is known as a zoonosis, that is, a disease transmitted to us by animals.
All zoonoses require special attention because it is unknown when they will transition from being a disease transmitted by animals to a disease transmitted between people.”
He gives the example of influenza as a zoonosis. Migratory birds are always carriers of the influenza virus, but at some point, it jumped to humans. This happens when the necessary mutations occur, producing viruses that are specifically for humans and can cause pandemics like the one in 2009.
He points out that in the case of hantavirus, it is difficult for it to be transmitted from person to person. Most of the hantavirus cases that have occurred in places as close as the United States or northern Mexico were transmitted through rodent droppings.
“These are isolated cases because these viruses, these types of viruses that we have nearby, do not have the capacity to pass from person to person, which is when the risk of an epidemic increases exponentially,” the expert said.
The Andes Virus
However, he points out that there is only one type of hantavirus, the one known as Andes, that has been shown to be transmissible between people, which implies a greater risk.
He explains that the current alert is primarily focused on this type of virus, Andes, given that a group of tourists traveling on a cruise ship contracted it.
The risk now is that this group of travelers, who have been in contact with other tourists, may have also been in contact with Mexicans, since they were gradually evacuated from Spain, where there is a large Mexican population.
He emphasizes that at any moment, a risky contact could occur that could spread the virus to other countries because “viruses don’t keep their word.”
Despite this, he reminds us that the Andes virus is transmissible from person to person, but its contagiousness is very low compared to other viruses such as influenza or measles.
Close and frequent contact with the carrier
He states that a person must be in close and frequent contact with the carrier to be exposed to the virus and for the other person to become infected. This can happen through hugs, kisses, or sexual contact, for example.
He explains that this is why people on the cruise ship became ill and caused the outbreak: because they were in close proximity, in an enclosed space, as the cold weather kept them indoors. The first infected individuals, a married couple from the Netherlands, then infected those who lived with them.
At least 10 people infected
So far, approximately 10 people who lived in close proximity to one another have been infected.
He points out that it is still unknown whether the first case was contracted off the ship, since passengers disembark at the port, eat, and walk around, or if an animal carrying the virus boarded the ship, thus spreading the infection.
-They could also have been infected during the voyage, since they went to Antarctica, which isn’t like a tropical cruise where you’re on deck and in the pools. In this case, they were in their cabins, so all the necessary conditions were in place for close contact and person-to-person transmission of the Andes virus, which is native to South America.
The fact that the travelers were elderly also contributed to the severity of the cases.
He noted that the actual extent of the exposure experienced by the passengers on that ship is unknown, and that they are currently dispersed among their respective countries under quarantine, which is essential since it has been observed that this virus can remain contagious even a month later.
For this reason, the alert and precautions are in place, although it is most likely that even if new cases arise, they will not spread beyond the virus’s own capacity.
The expert emphasizes that the risk, as with all viruses, is that in the future, or even now, it could mutate and become more efficient at transmitting from person to person. Currently, very close contact is required for infection, but the virus can mutate.
The good news is that hantavirus, particularly the respiratory strains, is quickly inactivated by heat, light, and humidity. It has poor transmissibility through these routes.
Mexico lacks special surveillance for hantavirus
Mexico does not have a specific epidemiological surveillance system for hantavirus. Therefore, most cases of hantavirus detected have been incidental. These cases are identified by identifying a person’s history of rodent exposure, after ruling out other possibilities, such as leptospirosis, which is frequently associated with rodents and has a significant number of cases in Yucatán.
Specifically in Yucatán, Dr. Narces Alcocer, in his practice, does not recall any registered cases of hantavirus, although the types of rodents found in the state can transmit the disease.
Symptoms Caused by the Andes Virus
Regarding the symptoms caused by the Andes virus, the specialist explains that it is characterized by respiratory symptoms, which is what differentiates it from the hantaviruses found in Europe or North America. The latter produce clinical symptoms very similar to dengue fever, such as hemorrhagic fevers, kidney failure, and others, while the Andes virus causes respiratory symptoms.
No Treatment or Vaccines for Hantavirus
The epidemiologist adds that there is no specific treatment or vaccine for hantavirus. Currently, the only recommendations issued as part of the alert involve supportive care, meaning that the patient’s symptoms are addressed according to their level of severity at any given time. If it is hemorrhagic, then treatment is given with IV fluids; if it is respiratory, then oxygen and ventilation are provided.
Some protocols, especially in South America and Europe, use anti-inflammatory drugs, such as steroids, but no antibiotics or treatments beyond addressing the patient’s general symptoms are available.
He points out that the Andes hantavirus is respiratory, while the other hemorrhagic types remain endemic, primarily in Europe and Asia. In both cases, symptoms initially manifest generally with fever, headache, joint pain, and malaise. This clinical picture usually lasts between one and four days, and after that time, while many cases are self-limiting and have no further symptoms, others progress to severe cases, potentially developing nephrotic syndrome (affecting the kidneys), hemorrhagic disease, and respiratory complications such as pneumonia or severe acute respiratory syndrome, which can be fatal in up to 50% of cases.
Hantaviruses that cause hemorrhagic diseases have a more moderate lethality rate, of approximately 10%.
Source: yucatan
