What's The Deadliest Virus In The World?
8 JUN 2018. 20:18
Viruses aren’t automatically your enemy. These ambiguous, definition-bucking little beasties, found in http://www.iflscience.com/plants-and-animals/newly-discovered-family-marine-viruses-happen-to-be-prolific-killers/all/" rel="nofollow - every single environment on Earth, play a variety of roles – and the ancient precursor to one seems to play a role in how we http://www.iflscience.com/plants-and-animals/bizarre-protein-that-influences-memory-behaves-a-lot-like-a-virus/all/" rel="nofollow - form memories . Saying that, plenty of viruses can cause lethal infections in humans, with some being deadlier than others.
Without a doubt, influenza is the https://naturemicrobiologycommunity.nature.com/channels/1469-centenary-of-1918-influenza-pandemic/posts/29273-100-years-of-the-great-influenza-pandemic" rel="nofollow - single biggest killer of them all. Back in 1918, between 50 and 100 million people died after being infected by the virus, which was around https://theconversation.com/the-greatest-pandemic-in-history-was-100-years-ago-but-many-of-us-still-get-the-basic-facts-wrong-89841" rel="nofollow - 5 percent
of the planet’s population at the time. Overall, half a billion people
were infected. Far from taking the lives of those that were otherwise
vulnerable – the already sick, the elderly, or the very young – it
spared no one.
There are several myths surrounding the pandemic, but it’s safe to
say that it was the deadliest mass infection in human history. In fact,
it’s something that plenty, including Bill Gates, have https://www.forbes.com/sites/michelatindera/2018/05/01/bill-gates-calls-for-and-funds-steps-to-prevent-a-global-pandemic/#10c999a73c05" rel="nofollow - warned could happen again if we take our eye off the ball, or if we https://www.theatlantic.com/science/archive/2018/05/ebola-returns-to-the-congo-just-as-trump-decides-to-rescind-ebola-funds/560012/" rel="nofollow - defund key agencies tasked with keeping the wolf from the door.
By total number of deaths, there’s no competition: The H1N1
strain of influenza virus is by far and away the most lethal in this
respect. What if, though, we look at the mortality rate of viral
infections instead – the number of infected people that ultimately die?
At a rough estimate, based on the high-end deaths value, H1N1’s case
fatality rate (CFR) back then was roughly 20 percent. As it turns out,
there are viruses that have frighteningly higher CFRs out there in the
world today.
Take http://www.who.int/en/news-room/fact-sheets/detail/rabies" rel="nofollow - rabies ,
for example. This is a disease that, according to the World Health
Organization (WHO), occurs in more than 150 countries around the world.
It’s present on every single continent, except Antarctica, and 99
percent of human transmissions occur through dog bites. Children aged
between 5 and 14 years are the most frequent victims.
Different variants have different incubation periods and
epidemiologies. Those with “furious rabies” can become hyperactive and
develop a fear of water and sometimes fresh air. A few days later,
cardiorespiratory arrest occurs.
Those with paralytic rabies take longer to die. It begins to
immobilize your muscles at the bite point, and eventually you fall into a
coma and die as your brain and spinal cord continually inflame.
Elke Muhlberger, an associate professor of microbiology at Boston University, told https://www.livescience.com/56598-deadliest-viruses-on-earth.html" rel="nofollow - LiveScience that without treatment, rabies is 100 percent fatal.
It is, however, vaccine-preventable, via the inoculation of dogs.
There are also treatments available for humans to have in case they get
bitten. In fact, every single year, more than 15 million people
worldwide receive a post-bite vaccination, which saves hundreds of
thousands of lives per annum.
Thanks to a comprehensive WHO Region of the Americas vaccination and
response program that began in 1983, the incidence of rabies in humans
and dogs has been reduced there by 95 and 98 percent, respectively. A
similar program is underway in South-East Asia. Today, deaths from
rabies aren’t that commonplace.
Then, there’s http://www.who.int/news-room/fact-sheets/detail/ebola-virus-disease" rel="nofollow - Ebola .
As noted by the WHO, Ebola first emerged in 1976 in two simultaneous
outbreaks in what is now South Sudan and the DRC. The infectious
malevolence has been in and out of the news over the last few years, and
the latest outbreak had public health experts scrambling to work out
whether or not it threatened those outside the Democratic Republic of
the Congo (DRC).
On average, those with the Ebola virus disease (EVD) have a 50
percent chance of dying – with a range of 25 to 90 percent in the past –
but early care, featuring rehydration and symptomatic treatment cuts
this somewhat.
It has several zoological reservoirs, and is easily spread between
people, which is why community education and engagement is key too.
Although plenty of experimental vaccination programs are underway, none
currently exist in the field, nor does the virus have a cure.
Dr https://www.nature.com/nmicrobiol/about/editors" rel="nofollow - Nonia Pariente , the senior editor of microbiology at Nature, told IFLScience that the http://www.afro.who.int/health-topics/marburg-haemorrhagic-fever" rel="nofollow - Marburg virus
has a particularly high CFR. Although a laboratory-linked outbreak in
1967 had a CFR of 25 percent, an Angolan outbreak in 2004 registered an
88 percent CFR.
Causing a viral hemorrhagic fever, it comes from the same Filoviridae viral
family as Ebola. It’s similarly virulent, and can easily jump from
human-to-human via physical contact and by handling dead infected
animals, particularly monkeys and fruit bats.
As with Ebola, no vaccine currently exists. It doesn’t affect many people around the world, though, and pretty much occurs near Rousettus aegypti, fruit bats that are natural reservoirs of the virus.
You could also include HIV here, but this is a complex one. These
days, an HIV diagnosis is often no longer synonymous with a death
sentence.
Phenomenal international health and biomedical research efforts means
that times have changed since the outbreak began in earnest a few
decades back: Those living with the infection not only can render
themselves virtually https://www.reuters.com/article/us-health-hiv-transmission-idUSKBN16G03N" rel="nofollow - unable to transmit the virus to others using medication, but they’re also able to live far more normal, longer lives.
As explained by the WHO, massively expanded access to http://www.who.int/gho/hiv/epidemic_status/deaths_text/en/" rel="nofollow - antiretroviral therapy
(ART), better public education, and prevention methods have led to a
“steep fall globally in the number of adults and children dying from
HIV-related causes.”
In 2015, about 1.1 million died from complications related to AIDS,
45 percent fewer than 2005, despite a period of substantial population
growth in regions where the disease is prevalent. The UN has committed
to ending the AIDS epidemic as a public health threat by 2030.
Saying all that, there is no cure for HIV: its ability to assault our
immune system makes it very difficult to deal with. The only person who
has been cured is the so-called http://www.sciencemag.org/news/2014/09/how-did-berlin-patient-rid-himself-hiv" rel="nofollow - Berlin patient , whose riddance of the virus from his system remains a mystery.
Mortality rates, therefore, vary wildly depending on the person’s
health and their access to ART. Those with HIV/AIDS won’t necessarily
die from it, but it does complicate things a lot. As noted by the http://hivinsite.ucsf.edu/hiv?page=basics-00-14" rel="nofollow - University of California San Francisco ,
a person diagnosed with HIV at 25 who receives solid medical treatment
is expected to live for 40 more years – but AIDS is a specter that waits
in many of their futures.
As is probably clear by now, a high CFR alone doesn’t make them more
dangerous than other viral infections. Mortality rate is just one factor
in the equation: How easy a virus can spread, the time it takes to
replicate within an infected host, the type of community in which
infection occurs, its ability to exist in various zoological reservoirs,
our ability to immunize ourselves from it, and how quickly and
effectively we as a species respond to an outbreak all play major roles.
“Most viral diseases that we can avoid is down to the fact that we
have effective vaccines to prevent them,” Pariente stressed. “Indeed, a
very big killer was eradicated thanks to vaccines, smallpox, and we are
on the verge for poliovirus.”
Measles, of course, is another potentially deadly viral infection.
Although almost eradicated in the last decade or so, Pariente laments
that anti-vaxxer nonsense has resulted in delayed progress and yearly
measles outbreaks now “notoriously in the US and Europe.”
Deadly viruses can sometimes be treated with drugs too, but there
aren’t many effective options available. “They replicate inside our
cells using a lot of our machinery, and so to make a drug specific is
hard," Pariente added. “If the drugs target the virus itself, they
frequently become resistant – through mutation, recombination,
re-assortment, depending on the virus.”
At the end of the day, what’s deadliest now – whether that be in
total number of deaths, CFR, or some other measure – doesn't always
remain so, as the future may present us with entirely new challenges.
Pariente pointed out that mosquito-borne viruses are proving to be
particularly problematic. They are hard to control and continue to
emerge and re-emerge in the tropics. Worryingly, “the mosquitoes that
carry them are extending their niche due to global warming and getting
into the US and Southern Europe.”
Dengue, Yellow Fever, Zika, and West Nile virus can all be spread
this way. Unsurprisingly, there’s a huge international health endeavor
underway to better understand their epidemiology.
Similarly, there’s also the worry that viruses may http://www.iflscience.com/health-and-medicine/the-next-pandemic-could-arise-in-your-dog-according-to-study/" rel="nofollow - suddenly change
to become far more deadly to humans than they were before. Influenza,
of course, is a good example of that, and sadly this type of event is
unavoidable. All we can do is make sure we’re as prepared as possible
for the next pandemic – whatever it is, and whenever it arrives.
Source and a couple of vaguely related videos: http://www.iflscience.com/health-and-medicine/whats-the-deadliest-virus-in-the-world/all/" rel="nofollow - http://www.iflscience.com/health-and-medicine/whats-the-deadliest-virus-in-the-world/all/
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