The World Health Organization warned the US and other countries about the risk of human-to-human transmission of Covid-19 as early as 10 January, and urged precautions even though initial Chinese studies at that point had found no clear evidence of that route of infection.

Technical guidance notes seen by the Guardian and briefings by top WHO officials warned of potential human-to-human transmission and made clear that there was a threat of catching the disease through water droplets and contaminated surfaces, based on the experience of earlier coronavirus outbreaks, such as Sars and Mers.

In recent days, Donald Trump has attempted to blame the WHO for the pandemic, pointing to a tweet from the group on 14 January saying there was no human-to-human transmission.

“In many ways, they were wrong. They also minimised the threat very strongly,” the US president said, before threatening to cut funding to the organisation.

Play Video 2:47 Donald Trump blames WHO for dire situation in the US, threatens to pull funding – video

Trump supporters have been calling for the resignation of the WHO’s director general, Tedros Adhanom Ghebreyesus, and for a congressional investigation of the body’s performance.

The January WHO tweet reported “preliminary investigations conducted by the Chinese authorities have found no clear evidence of human-to-human transmission”.

But in the same week top WHO officials were briefing health leaders around the world to keep looking out for signs of such transmission, and to take precautions as if it was already happening.

The WHO declared a “public health emergency of international concern” on 30 January, a day before Trump banned non-American residents who had been to China from entering the US. Nearly a month after the WHO declaration, Trump tweeted: “The coronavirus is very much under control in the USA”, adding that the WHO had “been working hard and very smart”.

Trump has pointed out that US funding of the WHO was more than 10 times China’s contribution, citing figures of $450m (£360m) and $42m, a reference to annual combined assessed contributions (membership fees) and donations. However, the US is currently about $200m in arrears in its assessed contributions, and donations are tied to specific projects.

Since the WHO launched a coronavirus emergency appeal, China has donated just over $20m, about the same as the UK, and the US has given less than $15m. Japan has donated $47.5m, Kuwait $40m and the European commission $33m.

Tedros has urged governments not to politicise the pandemic, warning on Wednesday: “We will have many body bags in front of us if we don’t behave.”

Play Video 1:19 Politicising Covid-19 like playing with fire, WHO director general says after Trump attack – video

The WHO director general said: “The United States and China should come together and fight this dangerous enemy … It’s like playing with fire. When there are cracks at national level and global level that’s when the virus succeeds. For God’s sake, we have lost more than 60,000 citizens of the world.”

The technical guidance notes published by the WHO on the 10 and 11 of January were issued when suspected infections in China comprised a few dozen cases.

The notes lay out detailed clinical criteria for dealing with suspected cases as well as warning of the risk of ease of transmission both by airborne droplets and contact with contaminated surfaces, suggesting isolation procedures.

As well as being posted online, the guidance was sent to the organisation’s regional emergency directors and country heads to be circulated to senior health officials.

One note, published on 11 January, advised clinicians and health officials to be alert to the emergence of clusters of cases as well as any “evidence of amplified or sustained human-to-human transmission” despite the Chinese, at that stage, not reporting sustained local transmission.

While the document advised medical personnel to look out for suspected patients who might have travelled to China’s Hubei province, or health workers who had contact with the then new virus, it also recommended that doctors look out for “unusual or unexpected clinical course, especially sudden deterioration despite appropriate treatment” regardless of those factors.

It added caution even if another clinical explanation had been advanced that appeared to “fully explain” the patient’s symptoms.

A day earlier, another guidance note on collecting samples from patients showing symptoms of the disease listed stringent precautions to avoid the risk of human-to-human transmission, using the experience from the Mers coronavirus.

The documents add to a body of emerging evidence of the widespread early warnings about the coronavirus, many communicated by – and to – senior US officials, which were ignored by Trump.

Trump scapegoating of WHO obscures its key role in tackling pandemic Read more

In a briefing at WHO headquarters on 14 January, the same day as the tweet about the Chinese results, the organisation’s technical lead on Covid-19, Maria Van Kerkhove, told reporters that while there had so far been only limited human transmission between family members in China, the risk of wider human-to-human transmission should not be regarded as “surprising” given the similarity to earlier Sars and Mers outbreaks.

An investigation in the Washington Post last week discovered a warning from US officials at the beginning of January relating to the threat of coronavirus.

On 3 January Robert Redfield, director of the US Centers for Disease Control and Prevention (CDC), spoke with his Chinese counterpart, George Gao, and was alerted to the newly emerging disease, becoming concerned enough for the CDC to establish an incident management structure for the new coronavirus on 7 January and activating its emergency response structure two weeks later, on 21 January.

Despite that move by the CDC, a day later Trump was insisting the situation was under control. “It’s one person coming in from China, and we have it under control. It’s going to be just fine.”