One of the greatest mysteries of coronavirus is how quickly it has spread around the world. The outbreak in Central China infection for three months was on all continents except Antarctica, having a serious impact on the daily lives of millions of people. The rapid spread of hid that caught scientists by surprise, has puzzled public health authorities and undermine efforts to contain the epidemic in its early stages, the virus may have spread seemingly healthy people.
In the background workers to return to offices, preparation for the resumption of classes in schools and opening of shopping centres and restaurants, scientists are concerned that if people, seemingly healthy, can transmit the disease, it may be impossible to keep.
It tells the Associated Press, the researchers found the likelihood of frightening the peaceful spread of the virus asymptomatic carriers. But what is the role of seemingly healthy people to replenish the ranks of the infected – this question remains unanswered.
About 4 out of 10 infected people never have symptoms. “To control, to actually prevent the return of the virus, we need to solve this problem,” – says an expert on tracking diseases at the London school of hygiene and tropical medicine Rhine Houben.
Scientists are watching to see how companies open up again, and wonder what will happen if Pacific distributors COVID-19 will not be detected until it is too late.
Travelers without coughing can slip past the screens of the airport. Working without heat will not fall under the control of temperature. People who are not feeling tired and sick, will attend a business meeting. And flash can start anew.
In January, reminds AP, there are signs that people could carry the virus without showing symptoms. 10-year-old boy in China, who went to Wuhan, had no symptoms but had a positive test result for coronavirus – like the six other members of his family who had cough and fever. Even more alarming was the message from Germany: on business trips from China the woman spread the virus among colleagues in Munich, although she looked healthy.
However, many scientists were not convinced. Some wondered whether the Chinese business lady did not have symptoms. They suggested that it could be lung ailments, which she attributed jetlag.
When there COVID-19, public health officials believed that it will be similar to other coronaviruses and that people are most contagious when they have symptoms such as cough and fever.
“We thought it was going to be like SARS: a long incubation period and lack of transmission during the incubation period,” – says an expert on modeling diseases from the University of Texas at Austin, Lauren Ancel Meyers.
At U.S. airports across the country travelers returning from the hot spots, including China, who had no symptoms, was allowed to go.
“We have assured ourselves and the public that contact with an asymptomatic person is not a danger,” says Dr. Jeff Duchin of the king County (Washington state), where in a big house to care Life Care arose the first large cluster of coronavirus in the United States.
Behind the scenes of such scientists as Myers, shared their disturbing findings with health professionals. Myers gathered a group of students who viewed the sites of Chinese health departments in search of data on onset of symptoms in situations where there was enough information to figure out who gave it to who.
In the period from 21 January to 8 February, they found several cases when the person that brought the virus home, the symptoms did not develop until the infection of a family member. For example, one woman in the Chinese city with several cases of the disease fell ill after her husband returned from a trip to town with a big flash. He got sick much later.
“When we looked at the data, we said, “Oh no, this can’t be true,” says Myers. – It was shocking”.
Discover more than 50 such cases, Myers immediately shared the analysis with the Centers for the prevention of the disease control and prevention, USA.
Specialist for monitoring of diseases at the London school of hygiene and tropical medicine Rhine Houben and his research team decided to create the example of the cruise liner Diamond Princess, a mathematical model to estimate the number of missed patients without symptoms. Four weeks later, their model showed that three-quarters of infected people on the ship were asymptomatic.
In Washington state, a group of researchers who studied the outbreak in the nursing home Life Care, found that health workers are spreading the virus to other institutions for the elderly. The experts believed that, at least, some of them worked while infected, but before symptoms appear. Then, in March, in another nursing home, it was found that over half the people with positive results had no symptoms, although most continued to develop them.
Around the same time, officials in Washington became aware of a cocktail party in an apartment in Seattle, where about 40% of guests were sick with coronavirus, although at the time no one seemed to get sick.
In other places, with the expansion of efforts in testing, showed a huge number of people without symptoms – from San Francisco to the aircraft carrier in the Pacific.
Flash, related with night clubs in South Korea, showed that more than 30% of cases were asymptomatic. In a new York maternity for about 88% of those who tested positive had no symptoms.
The nose and mouth serve as easy pathways for coronavirus. Once inside, the virus controls the mechanism of the cell to replicate itself, while fighting off immune defenses. The level of the virus increases rapidly in the upper respiratory tract, and all this with no symptoms in the first days of infection.
As it became clear that healthy people can spread the virus, U.S. health authorities have decided not to wait for scientific evidence. During a meeting in early March, senior representatives of health stated that they consider that the transfer may occur before people have symptoms. A few weeks later came the recommendation to close public areas nose and mouth masks, bandanas and even t-shirts.
Later after Chinese researchers published an article about what patients are most contagious for two to three days before symptoms appear. Evidence continues to accumulate, and the CDC now estimates that 40% of transmission occurs before people feel sick.
However, scientists remain in doubt. For many months, who have argued that asymptomatic dissemination was not the driving force of the pandemic, but recently did start to recognize the opportunity and encouraged people to wear masks.