Infectious Diseases 1
Despite advances in technology, one of the biggest threats to human survival comes from primitive [原始的] life forms.
Infectious [ɪnˈfekʃəs 传染性的] diseases are caused by micro-organisms [微生物], such as bacteria [细菌], viruses and parasites [ˈpærəsaɪts寄生虫].
These organisms have no access to education or technology, but they present a huge challenge to humanity [人类].
That’s because they are adaptable [有适应能力的].
Just as adaptability has helped humans survive, it makes it more difficult to control infectious diseases.
As conditions change, the organism which cause these diseases adapt and become stronger.
There are several kinds of infectious diseases.
Bacterial infections, such as pneumonia [njuːˈməʊniə 肺炎], are caused by bacteria.
These infections can be treated by antibiotics [ˌæntɪbaɪˈɒtɪks 抗生素], which kill the bacteria.
Viral infections are caused by viruses, such as the influenza [ˌɪnfluˈenzə 流感] virus.
These can sometimes be prevented by vaccines [ˈvæksiːnz 疫苗], such as flu vaccines.
An example of parasitic infection is malaria [疟疾].
Malaria is caused by parasites transmitted to humans by infected mosquitoes [məsˈkiːtəʊz 蚊子].
Once inside the body, the parasites can be difficult to kill or control.
And of course these parasites are also adaptable.
How serious are infectious diseases?
Consider what happened in 1918, the influenza pandemic [流行病].
It started in the fall of 1918 with what seemed to be something no more serious than the common cold.
In the next two years however, it infected a fifth of the world’s population.
In fact, it turned out to be the most deadly epidemic in history, killing between 20 and 40 million people.
The influenza virus that caused it was much stronger than previous influenza viruses.
Its mortality [mɔːˈtæləti 死亡] rate was two and a half percent (2.5%) compared to a point one percent (0.1%) in previous influenza epidemics.
It struck [碰,打击] quickly and without mercy, sometimes killing people within hours.
Schools and business closed in many places, and people wore masks to prevent transmission of the virus through the air.
What was unusual about this pandemic was that it was most deadly for people aged 20 to 40, rather than the elderly and young children.
听说
One of the biggest threats to human survival comes from primitive life forms.
Antibiotics attack and kill bacteria.
There are several kinds of infectious diseases.
Consider what happened in 1918, the influenza pandemic.
People wore masks to prevent transmission of the virus through the air.
Once inside the body, the parasites can be difficult to kill or control.
Infectious Diseases 2
Now, a century later, we have flu vaccines [ˈvæksiːnz 疫苗] that have reduced the severity [严重,痛苦] of the epidemics.
These vaccines need to be updated every year because the virus changes and new strains emerge.
What researchers fear is that a new strain [新类型] of the virus will develop and cause another pandemic.
Once an outbreak [爆发] occurs, transmission of the disease will be even faster than before.
An unintended [非计划的,无心的] consequence of our improved transportation system will be the speed at which an epidemic can spread.
Experts predict that the public health systems will be overwhelmed [难以承受] and unable to react quickly enough.
So the best defense will be to prevent an outbreak from occurring.
This will require global cooperation and the sharing of data.
It may also require changes in how humans interact with animals.
Animals, such as birds and pigs, carry viruses that may mutate [变异] into a strain that can infect humans.
Such a new strain could lead to another pandemic well before a new vaccine could be developed.
Since diseases and epidemics don’t stop at national boarders [寄宿生], this is a global issue requiring global action.
The threat of a global epidemic is another example of why we must learn to live together.
A new strain of a virus is ... a mutated form of the virus.
One danger is that an animal virus ... may mutate into a strain that can infect humans.
