What we know about the Delta variant

The Delta variant of the novel coronavirus is now spreading rapidly around the world.

The highly contagious variant, first identified in India in October, has been described by officials from the World Health Organization as "the fastest and fittest coronavirus strain".

So, what do we know about the Delta variant? How can we protect ourselves?

1. How widespread is the Delta variant?

The WHO announced on July 28 the Delta strain had spread to at least 132 countries, with the United Kingdom and India the most affected countries, where the variant accounted for nearly 90 percent of new confirmed cases.

2. How potent is the Delta variant?

A study conducted by the Centers for Disease Control and Prevention of the United States shows the Delta variant is nearly twice as contagious as previous variants. An individual infected with Delta variant can infect five to nine other people, and it is more likely to cause serious symptoms.

The US CDC said people infected with the Delta variant can remain infectious for 18 days, longer than the 13 days seen with the original virus.

According to a Chinese study, the concentration of virus particles in people infected with Delta virus is about 1,000 times higher than that of the original coronavirus strain.

3. What are the symptoms?

Typical early symptoms of the Delta strain are weakness, dysosmia or slight muscular soreness.

4. How is the Delta variant transmitted?

Like previous strains, the Delta variant is spread via respiratory droplets, close contact and aerosolized particles.

5. In what environments does the Delta variant spread?

Closed indoor environments are most conducive to transmission of the variant.

China's leading respiratory disease expert Zhong Nanshan said because of the high viral load of the Delta strain in carriers, masks should be worn in crowded or poorly ventilated places to prevent infection.

6. Do current vaccines protect against the Delta strain?

Preliminary research has shown Chinese vaccines are 100 percent effective in preventing serious COVID-19 symptoms from the Delta variant, 76.9 percent effective in preventing moderate symptoms, 67.2 percent effective against acquisition of mild symptoms and 63.2 percent effective in preventing a patient from becoming an asymptomatic carrier, according to Zhong Nanshan.