快猫短视频

Winter flu breaks out every year because small mutations in the flu virus let it dodge antibodies we made to protect us from the last flu we got. It isn鈥檛 totally different from that last flu, so we are partly immune, and the infection may be mild. But every now and then an influenza A virus breaks out carrying surface proteins that are very different. This 鈥減andemic鈥� flu spreads like wildfire regardless of the season 鈥� and often more, and younger, people die. Survivors do gain some immunity for next time, so the killer settles down and becomes regular seasonal flu, drifting along until the next pandemic flu surfaces.

1) 1510

Strain: unknown
Deaths: unknown
The first record : 鈥済asping oppression鈥� with cough, fever and difficulty breathing rapidly spread across Europe after reportedly arriving from Asia via Africa. Similar events were recorded throughout the 1700s and 1800s.

2) 1889-1890 Asiatic or Russian flu

Strain: H3N8 or H2N2
Deaths: ~1 million
The first pandemic to be spread faster by railways and steamships was recorded in St Petersburg in December 1889. Within four months, it had gone global, . Antibodies in survivors , and so perhaps related to the H3N2 flu dominating in this northern hemisphere winter.

3) 1918-1920 Spanish flu

Strain: H1N1
Deaths: 50-100 million
The , and the earliest to have its genome sequenced, it was called Spanish only because Spanish newspapers, free of wartime censorship, reported it first. A bird flu that adapted to mammals, no one knows where it started, but there are signs it was spreading . It got better adapted, and deadlier, as it spread, and exploded in autumn 1918, then in spring 1919. All human-adapted flu A since then descends from it.听

4) 1957-1958 Asian flu

Strain: H2N2
Deaths: 1.1 million
Flu carries its 11 genes in eight chunks of RNA. When a host is infected by two strains of flu, it can cough out hybrid viruses with chunks from both. This virus emerged when something, possibly a pig, combined the 1918 flu with two new genes for its surface proteins, H2 and N2, from bird flu. Children and young adults were especially badly affected: anyone under 39, so born after the beginning of the 1918 pandemic, would have caught the H1N1 virus first as children, so have strong immunity to that and weaker immunity to the emergent strain. Reported in Singapore in February 1957, then in London, Washington and Melbourne, the virus had swept the world by summer.听

5) 1968-1969 Hong Kong flu

Strain: H3N2
Deaths: ~1 million
This virus probably arose in then-secretive China, but was first reported to the world by UK newspaper The Times after it broke out in Hong Kong. The 1957 pandemic virus had gone on to become ordinary winter flu, but hybridised with a bird flu virus in some host infected with both, and emerged with a new H3 surface protein, the N2 surface protein from 1957, and most of the rest of its genes from 1918. This H3N2 is still circulating and dominating winter flu this season.

6) 1977 Russian or red flu

Strain: H1N1
Deaths: unknown
A new virus affecting people under 25 appeared in Russia in November 1977. But, as reported by 快猫短视频,. Thought to have been an experimental live animal vaccine that escaped, it was an H1N1 virus virtually unchanged from one that had circulated in the early 1950s. People born after 1957 had no immunity. Fortunately, its effects were mild.听

7) 2009 swine flu

Strain: H1N1
Deaths:
The 1918 pandemic virus persisted in pigs and in 1998 hybridised with other kinds of flu and spread like wildfire through US pigs, evolving rapidly. Virologists warned these 鈥渞e-assortants鈥� posed a pandemic threat: in 2009, it materialised on a US-owned hog farm in Mexico, when a re-assortant still carrying the 1918 H and N surface proteins broke out. It had circled the world by September. Death rates were low but in younger people than usual:听 people born before 1957 got immunity to the 1918 virus as children. Others had to wait till the first wave was over for usable quantities of vaccine to be manufactured.