WHO leaves health experts confused after asymptomatic comment

The World Health Organisation (WHO) left doctors and scientists scratching their heads after one of its officials announced at a press conference on Monday that Covid-19 patients with no symptoms 'very rarely' pass the virus on to others. 

"We have a number of reports from countries who are doing very detailed contact tracing. They are following asymptomatic cases, following contacts and not finding secondary transmission. It is very rare,” Dr Maria Van Kerkhove, WHO’s technical lead on coronavirus response, told journalists in a video conference.  

“We are constantly looking at this data and trying to get more information from countries to truly answer this question. It still appears to be rare that an asymptomatic actually transmits onwards.”

The statement contradicts multiple studies that have flooded the internet in recent months, arguing that asymptomatic patients are helping spread the contagious disease. 

Some experts immediately took to Twitter, questioning the WHO’s assessment. 

“@WHO communication here not stellar. If folks without symptoms truly "very rarely" spread virus, would be huge. But such a statement by @WHO should be accompanied by data,” Ashish K Jha, the dean-in-waiting at the Brown University School of Public Health, said in a series of tweets.

When approached by TRT World for clarification, a WHO spokesman refused to give an immediate comment, saying a Facebook live session for public and media would be held later in the day.  

It is vital to keep in mind the distinction between asymptomatic and pre-symptomatic cases. People in the pre-symptomatic category don’t show any visible signs for a few days but eventually end up becoming unwell. 

There are also those patients who have mild symptoms, known as paucisymptomatic infections, and can still be spreading the virus. 

The case of silent spreaders 

Multiple studies and experts at leading health institutions have said in recent months that coronavirus patients could be passing on the infection even if they don’t show any symptoms. 

One early study said that asymptomatic people were a source of infection for 79 percent of the documented cases in China. 

If the WHO’s new assessment becomes accepted, it will radically change many of the assumptions made about the virus that has so far killed more than 400,000 people around the world. 

For instance, the CDC Director,Dr Robert Redfield, said in a March interview to NPR, that the virus spreads rapidly in part because of asymptomatic people, which make up as much as 25 percent of the infected. 

Other studies such as the one conducted on 243 cases in Singapore said “presymptomatic transmission is the most likely explanation for the occurrence of secondary cases.” 

What made the coronavirus so worrying for doctors is the number of people who are believed to be spreaders but they themselves don’t show any symptoms. In Iceland, a study found that 50 percent of infected people were not showing any symptoms.

Experts have long cautioned that asymptomatic cases must be taken seriously and advised people to take precautions if they have come into contact with a confirmed Covid-19 case. 

“A growing body of results shows that people who are asymptomatic appear to have the same viral load as symptomatic cases,”  Gigi Gronvall, an immunologist and senior scholar at the Johns Hopkins Center for Health Security, said in an interview in May.

“If you're able to transmit the virus while asymptomatic, it allows for a lot more community spread.” 

How much of a viral load is needed to spread the deadly virus has been a question that has boggled scientists. 

Up until now, there has been no definite conclusion on the link between the severity of symptoms - such as cough or fever - and the viral load. 

Asymptomatic transmission is seen as a challenge for health authorities as it makes it difficult to track the infectious spread when people show no signs of illness and aren’t getting themselves tested, fueling concerns that there could be many more spreaders than known. 

One of the reasons that CDC advised people to wear a mask, going back on an earlier announcement, was the result of evidence that people with no symptoms could possible be virus spreaders.