Name: 有人得了登革熱會怎麼樣？ (What Happens When Someone Gets Dengue Fever?)
Uploaded: 2021-01-14T10:34:47.000Z
Duration: 7 min 52 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Dengue fever is a mosquito-borne disease caused by a virus of the same name.

It's a part of the Flaviviridae family, known for its other famous members: Yellow

It's also referred to as breakbone fever, but that should be the least of your concern...what

Most commonly found in tropical regions, Dengue puts 40-50% of the global population at risk.

With symptoms ranging from fever, rashes, painful joint and muscle aches to vomiting,

Dengue can resemble the flu, but it can become life-threatening in a much different way.

When the pH changes, it changes the configuration of the Dengue virus.

Actually, at that point I could grab the model.

I work at the California Academy of Sciences.

I'm curator of microbiology and chief of science, and I study the genetic makeup of Dengue viruses.

I've been working on it since 2000 and I was one of the first people to look at large swaths

of the Dengue virus genome to pinpoint where key mutations were occurring to drive its

To understand how Dengue spreads, it helps to start with how it gets in.

Enter, the mosquito: specifically a species called Aedes aegypti.

It actually prefers the crepuscular times of the day, so that's dawn or dusk, and it

It might feed three or four times in its lifetime, and that gives the Dengue virus ample opportunity

to be passed between human hosts by a single infected female mosquito.

Now, what makes these types of viruses so quick to take off, is their genetic architecture,

which allows them to begin producing proteins immediately after they enter the host cell.

Dengue virus has been an interesting puzzle for a lot of scientists and clinicians.

It is probably infecting almost 400 million people a year as far as we know, but only

a small fraction of people actually get sick, about 90 million a year.

So we're not really sure why some people get sick and other people don't get sick.

Once the Dengue virus gets in through the skin, it can take several days to a week eventually

find its way into your lymph nodes and, then, bloodstream.

From there, it's just one big fast-track to Flavivirus-town.

So Dengue's primary target and the way it sustains itself in your body is in white blood

cells, and these are macrophages and monocytes that are antibody receptor-bearing cells that

the Dengue virus uses to bind and enter the cell.

The cell is naturally taking anything that's bound to its receptors and phagocytizing it,

so basically pulling it into an internal cellular capsule, and once that happens, the pH of

And when the pH changes and that lock-and-key relationship between the virus protein and

the host cell receptor proteins experience that change in pH, a pore is formed... and

through that pore, the virus genome enters into the host's cytoplasm.

And from there it's a pretty sophisticated version of copy and paste.

The virus uses the host cell to duplicate itself.

In contrast, many people are familiar with other mosquito-borne diseases like malaria.

At the sporozoite stage as it's replicating in your red blood cells, it's copying itself

to a great degree until basically your host cell explodes or bursts open and spreads sporozoites

It's working with the host cell and taking advantage of host cell energy and metabolism

Dr. Bennett and her team study the genetic differences between the four serotypes of

Those differences and similarities are what makes co-circulating stereotypes a dangerous

combination, contributing to more severe episodes of the illness.

They are co-circulating today all over the world, but in the old days they didn't overlap

When they started to move around...we also saw more hemorrhagic fever and more severe

forms of the disease, so one hypothesis is because we're being exposed to multiple strains

of Dengue throughout our lifetime and that's creating this risk to develop severe disease.

And yes, hemorrhagic fever is just as bad as it sounds.

So what happens in a secondary infection is that those antibodies that you've produced

to the first one don't bind as efficiently to the Dengue virus.

Instead of being neutralized in the endosome, it can enter the host cell more efficiently

What we think is happening is that it's creating more infected cells than you would have in

the case of a primary infection or a re-exposure to that same primary serotype because of the

inefficiency and the lack of perfect match between the antibody and the new virus.

Typically, once your immune system fights off a disease, it remembers it for future

But with Dengue, immunity to one serotype doesn't protect you against a different

serotype, and can in fact enhance the infection, making a second or even third encounter with

the disease much worse...because your immune system's memory is stimulated but not a

We think that that is what's causing this out of control immune response that accelerates

and eventually leads to the hemorrhagic fever that we see and even in some cases shock syndrome.

So Dengue shock syndrome is another severe outcome of this over-reactive proinflammatory

One impact of having an overabundance of proinflammatory cytokines is that membranes become leaky,

and when capillary beds become leaky, blood will flow out.

And you start to bleed out into your capillary beds and into the tissues, and then fluids

to flow into your bloodstream causing potentially hypovolemic shock and death by Dengue shock

And both hypovolemic shock and fever can be deceptive.

The most frustrating phenomenon with Dengue virus is that people seem to start to recover.

They might have three to four to maybe seven days of fever depending on when they first

exhibit symptoms, and then the fever's starting to go down, we can sort of see the diminishment

of symptoms, and then hemorrhagic fever or shock syndrome can kick in very quickly after

So Dengue is not something to take lightly, but Dr. Bennett says these extreme cases are