Microsoft co-founder Bill Gates has called for a nationwide shutdown in the US as the number of COVID-19 cases surpassed 2,00,000 in the country.

“Despite urging from public health experts, some states and counties haven’t shut down completely. In some states, beaches are still open; in others, restaurants still serve sit-down meals. This is a recipe for disaster. Because people can travel freely across state lines, so can the virus,” he noted in an op-ed in the Washington Post.

Gates explained that businesses need to remain shut until the numbers of reported cases start to go down across the country, which, according to him, could take at least 10 weeks.

"Any confusion about this point will only extend the economic pain, raise the odds that the virus will return, and cause more deaths," he said.

COVID-19 Vaccine Frequently Asked Questions View more How does a vaccine work? A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine. How many types of vaccines are there? There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine. What does it take to develop a vaccine of this kind? Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time. View more Show

Gates also called for more testing hoped that a vaccine could be available before the suggested 18-month timeframe.

The COVID-19 pandemic has hit the US hard. The US has seen a significant rise in cases in the last month, and New York has now become the epicentre of the outbreak.

US President Donald Trump on April 1 warned the country to brace for a "painful" and "tough" two-week period as he extended the nationwide distancing measure to April 30.

Trump also said that more than 100,000 and up to 240,000 Americans could die due to COVID-19, a number which could surge up to millions if guidelines are not followed.