No pandemic threat from Hantavirus yet, human-to-human spread rare: Expert

The hantavirus outbreak aboard the Dutch expedition cruise ship MV Hondius, which was sailing from Ushuaia, Argentina, to Spain’s Canary Islands, has drawn global attention due to the serious nature of the virus. Prof Sunit K Singh, a renowned molecular virologist from BHU and currently the Director of the B R Ambedkar Centre for Biomedical Research (ACBR) and Delhi School of Public Health (DSPH), Delhi, speaks to TOI’s Binay Singh about the latest developments surrounding the virus. Excerpts

Q: What is hantavirus, and how does it spread?

A: Hantavirus is a member of the Bunyaviridae family and is classified as a negative-strand RNA virus. Rodents serve as natural hosts, with each hantavirus type linked to a specific species. In the wild, the virus sustains its zoonotic cycle through rodent-to-rodent transmission. Two distinct disease syndromes are caused by hantaviruses - Hantavirus Cardiopulmonary Syndrome (HCPS) and Hemorrhagic Fever with Renal Syndrome (HFRS). To enter human cells, hantaviruses use the beta 3 integrin receptor on cell surfaces. Hantaviruses are fundamentally zoonotic, meaning they are transmitted from animals to people. Most human infections result from breathing in virus particles that have become airborne from rodent urine, feces, or saliva, for example, when a space contaminated with rodent waste is disturbed or cleaned. Transmission can also occur by handling contaminated objects or ingesting food contaminated with the urine, feces, or saliva of infected rodents.

Q: Which Hantavirus has been reported in a cruise outbreak recently?

A: There are many known strains of hantavirus, but the most recent is the Andes virus, according to the World Health Organization (WHO). The Andes virus causes Hantavirus Cardiopulmonary Syndrome (HCPMS). The WHO reports that the current outbreak on the MV Hondius cruise ship is caused by an Andes virus, which severely affects the cardiac and respiratory systems. This strain of HCPS can be transmitted from person to person, although human-to-human spread is rare. Studies suggest that this variant has a mortality rate of up to 35-50%.

Q: What are the clinical features of HFRS and HCPS?

A: The early signs of all hantavirus infections are quite alike, typically featuring a sudden onset of high fever, general discomfort, muscle pain, and other symptoms resembling the flu. HFRS specifically causes acute damage to the kidneys and noticeable bleeding tendencies. These hemorrhagic signs may include tiny red spots (petechiae) on the skin and mucous membranes, larger bruises (ecchymoses), redness of the eyes (conjunctival suffusion), blood in the vomit, nosebleeds, blood in the urine, and black stools. In severe instances, low blood pressure and even shock can develop quickly. Meanwhile, kidney function temporarily declines, leading to reduced urine output or complete cessation of urination, along with proteinuria.

Q: Is it going to lead to a pandemic like Covid-19?

A: In contrast to viruses like SARS-CoV-2, hantaviruses do not readily transmit from person to person. Usually, people become infected with hantavirus through exposure to rodent droppings, urine, or saliva. However, the strain involved in this outbreak is Andes, which can be transmitted between humans, although such events are very rare. This potential for human-to-human transmission has raised concerns regarding the outbreak.

Q: What are the diagnostic tools available?

A: The diagnosis is primarily based on a combination of molecular and serological methods. Reverse transcription-polymerase chain reaction (RT-PCR) is critical for early diagnosis by directly detecting the virus's genetic material (RNA) in a patient's blood sample. Real-time PCR is a more advanced and specific technique that allows the quantification of the virus. The hantavirus genome can be detected in clinical samples such as blood, serum, or tissue at the onset of illness. Serological tests include the enzyme-linked immunosorbent assay (ELISA), which identifies virus-specific IgM and IgG antibodies. Other tools include immunofluorescence assays (IFAs) and immunoblot tests.

Q: What treatment options are available?

A: No licensed treatments, approved antivirals, or vaccines are currently available, so the treatment is mostly supportive in managing the disease's symptoms.

Q: How do you see this outbreak from a public health point of view?

A: Public health measures should emphasize strengthening early case identification, strong surveillance, and reducing the chances of exposure. I do not see a major epidemic/pandemic threat in this outbreak.