The Hantavirus outbreak on the
Dutch cruise ship MV Hondius, which set sail from Argentina on 1st April, has
raised alarm around the globe. The index patient appears to have boarded the
ship in Argentina. However, it is not clear where he acquired it.
As of May 8, the WHO reported
eight cases and three deaths on the cruise. It was also reported that a doctor aboard
the cruise ship who was attending to an index patient contracted Hantavirus.
Such contamination was probable because of close contact with a patient in a
poorly ventilated space for quite some period, that too, without any protective
equipment.
The ship finally docked in
Tenerife, in Spain’s Canary Islands, and Spain allowed its 147 passengers and
crew from 23 countries to disembark and leave for their respective countries,
with advice to remain in isolation. WHO recommended 42 days of isolation for
each person.
Medical experts opine that Hantavirus
is deadlier than COVID. But they also say that it is significantly harder for
Hantavirus to spread from person to person, for it requires prolonged contact
with a person who is sick and is shedding the virus. Though it is much less
transmissible from human to human, there are many opportunities for its easy
transmission on a cruise ship. But it is hard to see the outbreak continuing
for long in normal circumstances.
Most of the Hantavirus infections
are primarily acquired through contact with the urine, feces, or saliva of
infected rats or by touching contaminated surfaces. Usually, such exposures
occur while cleaning premises infested with rodents. Human infections are more
commonly reported from rural areas where rodents are common, and opportunities
for exposure are greater.
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What is a Virus? |
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A virus is a small piece of genetic information enclosed in a protective protein coat called a capsid. Generally, they are not considered to be alive, for they do not metabolize, grow, or reproduce on their own. Instead, they use the host cell’s material to make more copies of themselves. It’s like someone breaking into your kitchen and using your utensils, mixer, oven, etc., to make more copies of themselves with the recipe they brought in (genetic information). Some common types of viruses are: Influenza viruses, human herpes viruses, Coronavirus, Human papillomaviruses, Enteroviruses, Flaviviruses, Orthopoxviruses, Hepatitis viruses, Ebola virus, etc. Viruses usually enter our bodies through our mucous membranes, including the eyes, nose, mouth, penis, vagina, and anus. Some enter our body through a mosquito bite or a bite of a tick. Some of the common diseases caused by viruses are: Common colds, Flu, COVID-19, Chickenpox, Measles, HIV/AIDS, Polio, Rabies, Smallpox, Zika, Hepatitis, etc. The typical virus life cycle runs as follows: it interacts with the target cell and introduces its nucleic acid into it. This interaction occurs through the binding of the virus to a specific receptor domain on the cell. Once its nucleic acid is introduced, the host cell no longer replicates. Instead, it makes virus proteins. The viral proteins produced in one part of the cell and the nucleic acid replicated in another part somehow come together and form new virus particle. It is then expelled from the cell. It then infects the nearby cells. Immediately after infection, the body reacts by producing interferon and other immune-enhancing molecules known as cytokines, as a first line of defense against the virus. This response is called ‘innate immunity’. Adaptive immunity, i.e., production of antibodies for a specific virus, will occur much later, say 10-21 days later. Viruses spread in two ways: direct contact that includes blood-borne transmission, fecal-oral transmission, airborne spread by droplets or aerosols, contact with bedding, clothes, etc., and vector transmission. Indirect contact spread includes instances where mucus from a runny nose may get onto the hands, or the virus may be left on surfaces such as doorknobs, telephones, etc., and is picked up by another individual, who then touches his eyes or nose, resulting in infection. To curb the spread of the virus, people should stay away from the sick. And those infected by the virus must stay home. It is necessary to wash hands often with soap and water. An alcohol-based hand rub also serves the purpose. Linens, eating utensils, and dishes belonging to the sick should not be shared without thoroughly washing them. Frequently touched surfaces by the sick person must be cleaned and disinfected at home. |
The only Hantavirus capable of
human-to-human transmission is the Andes strain. It is endemic to Argentina,
which regularly reports cases of Hantavirus Pulmonary Syndrome (HPS) primarily
caused by the Andes strain. The primary driver of the virus is exposure to
infected long-tailed mice. But its spread between people requires prolonged
contact with a sick person in enclosed spaces or exposure to the sick person’s
body fluids.
The symptoms of HPS due to the Andes
virus appear 4-42 days after exposure. The early symptoms include fatigue,
muscle aches, particularly in the large muscle groups like thighs, hips, back,
and shoulders. Some may also experience headache, dizziness, chills, and
abdominal problems such as nausea, vomiting, diarrhea, and abdominal pain.
Following these preliminary
symptoms, the patient may face a sudden onset of respiratory distress and
hypotension. The onset of the cardiopulmonary phase is evidenced by various degrees
of compromise of respiratory function. In acute cases, patients may experience progressive
pulmonary edema and hypoxia. Fatal cases are characterized by severe compromise
in hemodynamic function. The overall fatality rate is reported to be around
30-35%.
Mild cases do resolve by
themselves. Nevertheless, they need supportive care to heal. For instance, if a
patient develops fluid in the lungs, he/she has to be put on a respirator, and may
even need to be put in ICU supportive care. However, no specific treatment
protocol has been established in the medical community.
During the 2018 outbreak,
Argentina implemented enforced self-quarantine. It also imposed some
limitations on large gatherings. Such restrictions appear to be effective in
containing the spread of the virus.
The World Health Organization has,
however, stated that Hantavirus remains a low risk because it is a zoonotic
disease that spreads primarily through rodent saliva but not through
human-to-human transmission. Nevertheless, India, given its crowded and
unhygienic urban habitations with poor sanitation infrastructure, cannot ignore
vulnerability to becoming a breeding ground for disease-carrying rodents. Our
public health delivery system being what it is, we may have to remain alert to
check its occurrence and control it well before it becomes a threat.
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