Coronavirus disease 2019 , the infection caused by a new coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first identified in the Wuhan province of China and declared a pandemic by the World Health Organization on March 12, 2020. 1 It is thought that the virus originated from an animal species, most likely the bat, which is a reservoir for this type of virus. 2 At the time of writing, over 7 million people have been infected worldwide and over 400 000 have died. The infection leads to primarily respiratory symptoms, and the elderly, men, those with comorbidities, the obese, those who are immunosuppressed, and people from black and other ethnic minorities are disproportionately affected with severe COVID-19. 1, 3 In this commentary, I will discuss the value of Twitter in keeping users up to date and helping them identify trends of relevance to hemostasis and thrombosis.
The COVID-19 pandemic has resulted in a tsunami of information in scientific journals as well as on social media. During any pandemic, the thirst for information is almost as great as the search for treatments. During the 1918 Spanish flu pandemic, when the main way of disseminating information was through print media, newspapers released up to six editions daily. In 2020, constant delivery of information is made possible through the almost universal availability of the Internet. The only thing that outstrips the exponential number of new SARS-CoV-2 infections is the number of new pieces of information about the virus published daily online or in print. There are now many ways to communicate, including television, radio, newspapers, journals, and multiple social media platforms.
One way to keep up with the massive amount of available information is through the use of Twitter, which has very wide, | 723 MAKRIS instantaneous reach. Twitter divides people, with users swearing by it and nonusers considering it a waste of time. In my view ,   Twitter is now one of the most important ways to share knowledge with other scientists and the public, both rapidly and simultaneously. The number of manuscripts published on COVID-19 has been huge, with more than 300 per day during May 2020 ( Figure 1 ); it is impossible for a single individual to read them all.
Twitter has been invaluable in helping to identify and share the most important ones.
The reach of standard publications in science is relatively small, slow, and not always in a format that would be understandable to most people. Twitter facilitates this by being widespread, quick, and simple. Since the start of the pandemic, almost 11 million tweets have been posted that include the hashtag #COVID19. An example of a tweet and its reach is shown in Figure 2 . I started tweeting about COVID-19 to try and stay up to date in a very rapidly moving field and to share information I thought was important with a wider audience, both health professionals and the public. As seen in Table 1 , each tweet is read by thousands of people, and the number of impressions per month are many times higher than scientific publications in journals can ever achieve.
SARS-CoV-2 is an RNA virus that enters the cell through its receptor angiotensin-converting enzyme 2 (ACE-2), after which it is internalized. ACE-2 converts the vasoconstrictor angiotensin II (Ang II) to angiotensin 1-7, a vasodilator. Following infection, ACE-2 is downregulated, and the resulting increase in Ang II contributes to endothelial damage. Endothelial damage is one of the critical elements in SARS-CoV-2 pathogenicity, changing the microenvironment from thromboprotective to highly prothrombotic. 4 The increasingly prothrombotic environment leads to pulmonary microthrombi in a process called pulmonary intravascular coagulation (PIC). PIC leads to impaired oxygen exchange and respiratory failure. 5 
The initial publications from China recognized coagulation activation as being very common in COVID-19. 6 The D-dimer level on hospital admission correlated with disease severity, and progressive elevation in the intensive care unit (ICU) patients correlated with death. 7 The use of heparin prophylaxis, which was not initially routinely used in China, was associated with improved overall survival. 7 What was at first not reported from China was the very high prevalence of pulmonary emboli in patients in the ICU ( Table 2) . It is not clear if this was due to a reduced thrombotic risk in Chinese patients or the lack of systematic investigation of patients for thrombosis. 
Faced with a disease that has an ICU mortality of 30%-50%, a large number of off-label drugs have been used alone or in combination, based on theoretical or in vitro evidence of possible benefit.
Randomized controlled trials (RCTs) have been uncommon, and these drugs have been used largely outside clinical studies. The result is that many patient populations worldwide have been repeatedly exposed to the same noneffective medications. Had a good quality RCT been done initially, thousands of patients worldwide might have been spared these ineffective treatments subsequently.
However tempting it is to try something in a critical situation, all drugs have adverse effects and these can be detrimental. The call for RCTs in epidemics and pandemics is not new, and most of the arguments we have seen with COVID-19 were also suggested during previous epidemics. 9
This will have an impact on all of us, and the lessons from the 1918 Spanish flu pandemic, where early abandonment of isolation measures resulted in a larger second wave of infections that killed more people, must not be forgotten. 10 Countries are dealing with the loosening of lockdowns differently, claiming to follow scientific advice, and often interpreting the evidence in different ways. These decisions cannot be separated from the economic ones, and politicians take responsibility for making them. Implementation of testing,
tracking, and isolating contacts should be essential to limit infections. Many believe that the way out of the SARS-CoV-2 era will be through the use of a vaccine, even though there is no certainty that an effective one will be available. Twitter is the ideal platform for dissemination of information about rapid developments, which would F I G U R E 2 Example of a tweet with the analysis provided by Twitter. Impressions is the total number of times the individual tweet has been seen by users. Engagements is the total number of users who interacted with a tweet, such as by retweeting, replying, liking, opening a link, etc be impossible to achieve at the same rate in the traditional scientific print journals.
One aspect of SARS-CoV-2 infection that has not made an impact in the print literature yet but has gained traction on social media is the long-term complications in patients with COVID-19 pneumonia, especially in those who have required ventilation. It is essential that these patients are followed up prospectively to identify problems related to pulmonary, vascular, psychological, cardiac, and neurocognitive systems. Of major interest will be the frequency of long-term interstitial lung disease and pulmonary hypertension. It is assumed that a COVID-19-related pulmonary embolism can be treated with 3 months of anticoagulation as this is a transient risk factor, but this may not be the case, and the long-term thrombotic risk may be higher. 