There is "no question" that changes in temperature, rainfall and humidity are driving infectious disease outbreaks around the world, but the impact of rapidly changing weather systems on the coronavirus are not yet known, World Health Organization officials said Wednesday.

Even though scientists are still learning about Covid-19, the virus has shown the capability to "accelerate in a number of different climates," Dr. Maria Van Kerkhove, head of WHO's emerging diseases and zoonosis unit, told reporters during a press conference at the agency's headquarters in Geneva.

"If you remember, this began in very cold temperatures, very dry temperatures, very low-level humidity," she said. "We don't know how this virus is impacted completely yet."

China reported its first known cases of the coronavirus to the international health agency on Dec. 31 when parts of the country were in the middle of the winter season. Since then, the virus has spread to nearly to every country across the globe and infected more than 2 million people in a range of different environments.

Dr. Mike Ryan, executive director of WHO's health emergencies program, said that there are many other known diseases that are "climate-sensitive."

"You've seen outbreaks of cholera all around the world that are either related to flooding or related to drought, they are either related to too much water or too little water," he said.

Ryan said certain environments, such as densely populated cities, can also increase infectious disease risks.

Pakistan, which has more than 6,000 Covid-19 cases as of Wednesday afternoon, has struggled to clear coronavirus infectious in some of its larger urban cities, Ryan said. The population density in New York City, which has about twice as many people as Los Angles, is believed to have helped drive the coronavirus outbreak there.

"In many ways, unfortunately, those populations are almost like kindling for a fire and not just a fire of Covid but any other number of diseases," he said.

The virus has often been compared to the seasonal flu, which also sickens millions of people each year.

Last month, U.S. health officials warned that Americans need to prepare for a second cycle of the outbreak in the United States. Scientist say the virus could be seasonal and relent in warmer conditions just like the flu, but that also means it could come back in the fall.

"Would this possibly become a seasonal cyclic thing? I've always indicated to you that I think it very well might," Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said a White House press briefing on March 25.

"What we're starting to see in the Southern Hemisphere of Southern Africa and the Southern Hemisphere countries, is that we're having cases that are appearing as they go into their winter season," he said. "If they have a substantial outbreak, it will be inevitable that we need to be prepared that we'll get a cycle a second time."

Scientists are also still learning about the viruses origins. Earlier in the outbreak, scientists said the coronavirus that emerged from a seafood market in Wuhan, China, likely originated in bats and then jumped to an "intermediate host," possibly pangolin.

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