人類的祖先可能曾經居住過樹林，但隨著森林變成草地，迫使早期的人類發展出用兩隻腳行走。德國波茨坦大學（University of Potsdam）的地球科學博士後研究員亨利．維切拉（Henry Wichura）表示：「環境的改變或多或少都影響了兩足運動的產生。」而這困擾科學家已久的時間點，終於隨著喙鯨化石的出土出現曙光。研究發現，抬升的時間大約介於一千三百五十萬到一千七百萬年前。
猶他大學（University of Utah）地質學教授法蘭克．布朗（Frank Brown）表示：「生物的每個樣本都能訴說很多關於地球的歷史，有時候它們會出現在意料之外，這次就是個例子。」鯨魚的頭骨化石不但確定了東非高原地形的改變時間，對於環境改變人類行走方式和居住環境的時間點，科學家也有了更進一步的斷定和依據。
Wichura, H., Jacobs, L. L., Lin, A., Polcyn, M. J., Manthi, F. K., Winkler, D. A., Strecker, M. R., Clemens, M. (2014). A 17-My-old whale constrains onset of uplift and climate change in east Africa. Proceedings of the National Academy of Sciences, 25775586
但當時第一次世界大戰的主要參戰國家，如德、英、法、美等國為了避免影響士氣，嚴格管制媒體報導疫情。然而保持中立而未參戰的西班牙，因為沒有實施戰時審查制度，西班牙媒體自由報導著流感相關新聞，甚至連西班牙國王阿方索十三世（King Alfonso XIII）感染重症的消息也被廣泛報導，造成西班牙疫情特別嚴重的錯覺，也因此被命名為「西班牙流感」。
病毒外殼上還零星分布M2離子通道蛋白（M2 ion channel protein），但數量非常少，平均每100至200個HA，才有一個M2。套膜下則有M1基質蛋白（matrix protein M1）支撐病毒結構，維持病毒穩定。B型流感病毒的整體結構和A型非常類似，只是膜蛋白組成略有不同，除了HA和NA之外，另有兩種B型流感獨有的NB和BM2蛋白。至於C型流感病毒，外型就和A、B型明顯不同，它們在感染細胞表面時，能形成長達數百微米的「繩索狀結構」。
Bouvier, N. M., & Palese, P. (2008). The biology of influenza viruses. Vaccine, 26 Suppl 4(Suppl 4), D49–D53.
Berche P. (2022). The Spanish flu. Presse medicale (Paris, France : 1983), 51(3), 104127.
Yoshida, A., Uekusa, Y., Suzuki, T., Bauer, M., Sakai, N., & Yamauchi, Y. (2025). Enhanced visualization of influenza A virus entry into living cells using virus-view atomic force microscopy. Proceedings of the National Academy of Sciences of the United States of America, 122(38), e2500660122.
COVID-19 is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic.
The symptoms of COVID‑19 can vary but often include fever,[7] fatigue, cough, breathing difficulties, loss of smell, and loss of taste.[8][9][10] Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms.[11][12] Of those who develop symptoms noticeable enough to be classified as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction).[13] Older people have a higher risk of developing severe symptoms. Some complications result in death. Some people continue to experience a range of effects (long COVID) for months or years after infection, and damage to organs has been observed.[14] Multi-year studies on the long-term effects are ongoing.[15]
COVID‑19 transmission occurs when infectious particles are breathed in or come into contact with the eyes, nose, or mouth. The risk is highest when people are in close proximity, but small airborne particles containing the virus can remain suspended in the air and travel over longer distances, particularly indoors. Transmission can also occur when people touch their eyes, nose, or mouth after touching surfaces or objects that have been contaminated by the virus. People remain contagious for up to 20 days and can spread the virus even if they do not develop symptoms.[16]
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Testing methods for COVID-19 to detect the virus’s nucleic acid include real-time reverse transcription polymerase chain reaction (RT‑PCR),[17][18] transcription-mediated amplification,[17][18][19] and reverse transcription loop-mediated isothermal amplification (RT‑LAMP)[17][18] from a nasopharyngeal swab.[20]
Several COVID-19 vaccines have been approved and distributed in various countries, many of which have initiated mass vaccination campaigns. Other preventive measures include physical or social distancing, quarantining, ventilation of indoor spaces, use of face masks or coverings in public, covering coughs and sneezes, hand washing, and keeping unwashed hands away from the face. While drugs have been developed to inhibit the virus, the primary treatment is still symptomatic, managing the disease through supportive care, isolation, and experimental measures.
