"We are proud to have partners like Facebook and WhatsApp, that are supporting us in reaching billions of people with important health information", said Dr Tedros Adhanom Ghebreyesus, Director-General of the WHO.
"Of course, we must exercise caution; the situation can reverse".
The agency said the messaging service will provide the latest situation reports in real-time to help decision-makers in carrying out their roles. "It's also motivation to double down and do everything we can to stop transmission and save lives".
He said he is grateful so many people are, "spreading the word and not the virus", adding, "everyday, we are learning more about this coronavirus and the disease it causes".
"This easy-to-use messaging service has the potential to reach two billion people and enables World Health Organization to get information directly into the hands of the people that need it", the World Health Organization said in a statement.
The service, launched on Friday, was established in the hope of keeping people safe from coronavirus by providing accurate information to those concerned about the virus. "Don't smoke. Smoking can increase your risk of developing severe disease if you become infected with COVID-19", he said. With over 47,000 cases, the European nation has reported over 4000 deaths.
He said the organisation had discovered that though older people were the hardest hit, younger people were, however, not spared from the virus. "Thank you for heeding our call for solidarity".
Amid global shortages of protective gear for health workers and diagnostic tests, Chinese producers have agreed to supply the WHO, he said.
Whilst advising people to maintain their mental and physical health during the crisis, including exercising and eating a healthy diet to help the immune system, Tedros also had a message for the world's smokers.
Currently, WHO Health Alert service is available only in the English language.