The variety of circumstances and deaths within the coronavirus epidemic in China jumped sharply on Thursday because the authorities there modified how they maintain monitor of the illness, and never, primarily, due to any change within the form of the outbreak.
There may be nonetheless a whole lot of uncertainty in regards to the true numbers — as with all new illness — and that may proceed for the foreseeable future. Underscoring that time, hours after China revised its figures, the World Well being Group put out a decrease set, saying that for now, it could not change the way in which it counts.
However consultants say there have been good causes for altering the way in which sufferers with the illness, newly named Covid-19, had been counted, and the brand new strategy ought to catch many circumstances that had been missed earlier than. That can enable extra sufferers to get therapy and be quarantined quicker.
Here’s a have a look at what we all know — and what we don’t — in regards to the new coronavirus numbers and what they are saying in regards to the scope of the disaster.
How did the numbers change?
For a number of days, the Chinese language authorities had reported figures that steered the unfold of the illness was slowing, however that modified abruptly on Thursday.
Officers in Hubei, the Chinese language province that’s the epicenter of the outbreak, stated there had been greater than 48,000 circumstances there, a 44 p.c soar from the day earlier than. In addition they reported 1,310 deaths, a 23 p.c improve. The pattern continued on Friday, although not as markedly, when Hubei officers disclosed one other 4,800 circumstances and 116 extra deaths.
Beforehand, circumstances had been counted provided that sufferers examined constructive for the brand new virus. Now, the figures seem to incorporate anybody who has a CT scan of the lungs exhibiting a telltale sample of pneumonia.
Within the quick run, the brand new accounting might deepen confusion in regards to the true dimension of the epidemic. It additionally complicates efforts to trace the expansion of the illness during the last a number of weeks.
“We need to be careful in interpreting these numbers,” Dr. Michael Ryan, the World Well being Group’s emergency responses chief, stated on Thursday. The bigger variety of circumstances, he stated, “doesn’t symbolize a big change in the trajectory of the outbreak.”
The W.H.O. then released its own figures, leaving out the diagnoses made without a positive test for the virus — and indicating that it did not fully understand the change China had made.
“For consistency, we report here only the number of laboratory-confirmed cases,” the organization said in a situation report. “W.H.O. has formally requested additional information on the clinically diagnosed cases, in particular when these have occurred in the course of the outbreak and whether suspect cases were reclassified as clinically diagnosed cases.”
The W.H.O. reported almost 47,000 confirmed cases worldwide, fewer than 1 percent outside mainland China. The Chinese figures put the total at more than 61,000 cases.
What was wrong with the old way of counting?
In a word, plenty.
Kits to test for the virus are not being produced quickly enough to keep up with demand, and they take days to produce results. Using CT scans means more patients can be checked, with the results available almost immediately.
And the tests for the virus have not been very reliable. Many sick people have tested negative, only to test positive later. That appears to be, at least in part, because standard testing involves swabbing nasal passages and the throat, while the virus may be lodged in the lungs.
In the United States, the Centers for Disease Control and Prevention shipped hundreds of testing kits to state laboratories — and days later revealed that some of them were faulty. It is not clear whether China has experienced similar problems in making the tests.
So are the new numbers definitive?
There are several ways cases might still be missed. Some people get sick, and die or recover, without ever seeing a doctor. CT scans allow doctors to identify people whose infections have caused pneumonia, which can be fatal, but the scans will not catch people with milder symptoms.
There is another source of confusion about the numbers. It was reported this week that China is no longer counting as confirmed cases people who test positive for the virus yet show no symptoms. But some experts said they were not sure what had actually changed.
The Chinese health authorities say they can distinguish, on a CT scan, pneumonia brought on by the coronavirus from some other serious lung diseases. But it is not clear that they can tell it from pneumonia caused by other diseases, like seasonal influenza; the accuracy may vary with the skill of the doctor reading the scan.
Will we eventually get more accurate figures?
Right now, labs are testing for the virus itself, and viruses can be hard to detect. What is often easier to identify is the immune system’s own response.
When a patient contracts an infection, the body produces antibodies to it — proteins in the blood that recognize a particular pathogen and trigger an immune system attack on it. Labs around the world are working to develop a test for antibodies to the new coronavirus, but none is available yet.
It could be tricky.
There are several strains of coronavirus in humans, including ones that cause common colds, SARS and MERS. Antibodies to the new virus may be hard to distinguish from the antibodies people already have to other coronaviruses.
In any case, it can take days or weeks before a patient tests positive for antibodies to a new infection, so the test may not be useful in diagnosing current illnesses.
So while an effective antibody test may produce a fairly comprehensive picture of an outbreak, that picture will lag a bit behind the reality.