It has infected more than million others, and new variants threaten another surge in cases even as vaccines have begun to roll out.
Now imagine if it were even more infectious — if the number of people each infection caused were closer to between five and seven. Currently, the coronavirus kills around 0. Instead, imagine that it killed 30 percent — and that it would take centuries, instead of months, to develop a vaccine against it. But humanity only made the transition into that new world fairly recently. And smallpox eradication was a big part of it. In the 20th century alone, the disease killed hundreds of millions of people.
Its gradual eradication meant ending the needless suffering and death of millions and millions of people every year. As we learn how to address current and future pandemics, it is worth understanding what we learned from the great infectious disease fights of the past. Smallpox has been around for a very long time. It devastated the Americas in the early s after being introduced through contact with Europe.
Its toll throughout history is hard to measure, but in the 20th century alone it is estimated to have killed between million and million people. Henderson , former director of disease surveillance at the Centers for Disease Control and Prevention, wrote in his book Smallpox: The Death of a Disease , noting that even the most devastating wars of the 20th century — World War I and World War II — had a combined death toll much smaller than that of smallpox.
Smallpox was spread by a virus technically, two viruses: Variola major and the significantly less common Variola minor. The more serious strain, Variola major, killed about 30 percent of people infected with it, with even higher death rates in infants.
Death usually occurred within eight to 16 days. Variola minor had similar symptoms but was much less deadly, with death rates around 1 percent. No effective treatments were discovered by the time the disease was eradicated. But the Covid pandemic prompted an epidemiological crash course for many of us, which ought to give us a new perspective on the horror of smallpox. The disease, like Covid, was primarily transmitted through close contact, especially in indoor spaces.
Our best estimate, though, is that it was easier to transmit than Covid, with an R0 estimated to be between 5 and 7 , even higher than the new coronavirus variants with an estimated R0 of 4.
Between the high R0 and the devastating mortality rate, it was not uncommon for an outbreak of smallpox in an area without preexisting immunity to kill 30 percent of everyone in the community. In some contexts, such as when it spread through the Americas after being introduced by Europeans, the death rate is believed to have been even higher. Before modern vaccine development, humans had to get creative in slowing the spread of infectious disease. In China, as early as the 15th century, healthy people deliberately breathed smallpox scabs through their noses and contracted a milder version of the disease.
Between 0. In England, in , doctor Edward Jenner demonstrated that contracting cowpox — a related but much milder virus — conferred immunity against smallpox, and shortly after that, immunization efforts began in earnest across Europe. By , the US Congress passed legislation to ensure the availability of a smallpox vaccine that reduced smallpox outbreaks in the country throughout the s. In the rest of the world, similar efforts were undertaken, with varying levels of commitment and success.
In the new research report appearing online in The FASEB Journal , researchers describe how the virus cripples immune systems by attacking molecules made by our bodies to block viral replication.
In a high containment laboratory at the Centers for Disease Control and Prevention in Atlanta, scientists produced the recombinant proteins from the variola virus and a similar virus that affects monkeys, causing monkeypox. The researchers then showed that cells infected with variola and monkeypox produced a protein that blocks a wide range of human interferons, which are molecules produced by our immune systems meant to stop viral replication.
Generally, it takes prolonged, face-to-face contact - of the kind that takes place in a household setting - to spread the disease from one person to another. It can also be spread through direct contact with body fluids, or objects like bedding and clothing. It can also be spread through the air in buildings or other enclosed spaces, although that happens less commonly.
There is currently no proven treatment for smallpox. However, it can be prevented through vaccination. The vaccine can still protect people even after they've already been exposed to the smallpox virus. Vaccinating within seven days will tend to lessen the severity of any illness resulting from exposure to smallpox.
However, the vaccine can cause serious, potentially fatal reactions in some people, so the benefits of vaccination need to be balanced against the risks. At a minimum, it's been estimated that roughly one out of every million people who receive the vaccine will die - and 15 will become very seriously ill.
And unless someone does use the disease as a weapon, the risk of becoming ill with smallpox is zero. People no longer receive routine smallpox vaccinations. The smallpox vaccine can have potentially fatal side effects, so only the people who are at high risk of exposure get the vaccine. Historical accounts show that when someone was infected with the smallpox virus, they had no symptoms for between seven and 17 days. However, once the incubation period or virus development phase was over, the following flu-like symptoms occurred:.
These symptoms would go away within two to three days. Then the patient would feel better. However, just as the patient started to feel better, a rash would appear. The rash started on the face and then spread to the hands, forearms, and the main part of the body. The person would be highly contagious until the rash disappeared. Within two days of appearance, the rash would develop into abscesses that filled with fluid and pus. The abscesses would break open and scab over.
The scabs would eventually fall off, leaving pit mark scars. Until the scabs fell off, the person remained contagious. There were two common and two rare forms of smallpox.
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