LONDON - Scientists and public health officials are beginning to get a better understanding of the coronavirus that has spread rapidly in China and increasingly around the world.
But significant gaps remain.
Important findings have emerged from scrutinising early cases of the novel coronavirus from China as health officials race to slow the spread of the pneumonia-like disease, which has infected more than 2,000 people, most of them in China.
The first clinical data published on the lethal Sars-like virus suggest it has a stealthy quality in its early stages that could allow it to evade detection, Bloomberg reported.
Two studies published on Friday (Jan 24) in The Lancet medical journal depict "a disease with a three to six day incubation period and insidious onset" with fever, cough and muscle pain, Dr David Heymann, an infectious disease specialist at the London School of Hygiene & Tropical Medicine, wrote in a commentary in the journal.
Some patients have mild disease, but older patients, aged over 60, progress to severe acute respiratory distress syndrome and need intensive care.
He said the two studies provided valuable early insight on the virus because they confirm that many patients had contact with the seafood market that is the suspected source of infection, while others did not but had contact with patients in their family cluster or elsewhere.
"Although these reports confirm person-to-person transmission, the means of transmission and the transmissibility cannot be hypothesised from the information published," he said.
According to The Guardian, researchers said they need to quickly find out whether most cases have been caused by repeated spillover of the virus from animals into humans, or whether most cases are now being triggered by secondary human-to-human transmission.
"That would be the big epidemiological goal for everyone at the moment," Dr Trevor Bedford, an evolutionary geneticist at Fred Hutchinson Cancer Research Center in Seattle, Washington, told the journal Nature.
Genetic analysis of various strains of the new virus, called 2019-nCoV, detected in patients shows the strains are remarkably similar to each other.
This lack of genetic diversity suggests the common ancestor of these different strains only emerged recently, possibly in November or December, said The Guardian.
However, research does not yet say whether the recent rapid expansion of the virus took place in humans or in an animal reservoir.
The new virus is most closely related to coronaviruses that have been found in Chinese horseshoe bats, according to the report.
Other coronaviruses that have jumped to humans, including severe acute respiratory syndrome (Sars), have been linked to bats.
While the World Health Organisation stopped short of calling the new virus a global health emergency, the number of deaths has risen to 56 and the number of confirmed infections is rising quickly.
The first cases of the new virus emerged in the Chinese city of Wuhan, centring on a large seafood market.
In the first of the two case studies published in The Lancet, initial data from that city show some similar symptoms between the first 41 cases of the virus and Sars.
About one-third of the 41 patients developed acute respiratory distress syndrome or were admitted to intensive care, and six died, according to the study.
The median age of the 41 patients was 49. Two-thirds had been to the seafood market that also sold wild animals for meat and is thought to be the place the virus jumped from an animal source to people.
All had pneumonia, most had fever and a cough. Some had fatigue; rarer symptoms included headache and diarrhoea. Most had been healthy until they contracted the virus.
Despite similar symptoms to Sars such as fever and shortness of breath, there are also key differences, including the absence of upper respiratory tract symptoms and intestinal sickness, according to Bin Cao, lead author from the China-Japan Friendship Hospital and Capital Medical University in China.
The second study published in the Lancet focused on person-to-person transmission and inter-city spread of the virus in a family in China.
Six members of the family travelled to Wuhan from Shenzhen between Dec 29 last year and Jan 4.
"Of six family members who travelled to Wuhan, five were identified as infected with the novel coronavirus.
"Additionally, one family member, who did not travel to Wuhan, became infected with the virus after several days of contact with four of the family members," according to the study.
The patients arrived at the University of Hong Kong-Shenzhen Hospital in Shenzhen six to 10 days after the onset of their symptoms, wrote Dr Jasper Fuk-Woo Chan, from the hospital's Department of Clinical Microbiology and Infection Control, in the study which was co-authored by more than a dozen other colleagues.
None of the family members had contacts with Wuhan markets or animals, although two had been to a Wuhan hospital to visit sick relatives, the authors said.
Five family members, aged between 36 and 66, developed fever, upper or lower respiratory tract symptoms, or diarrhoea, or a combination of these three to six days after exposure, the study said.
On Sunday, China's National Health Commission Minister Ma Xiaowei told reporters that the authorities' knowledge of the new virus was limited and they are unclear on the risks posed by mutations of the virus.
He said the incubation period for the coronavirus can range from one to 14 days, and that the virus is infectious during incubation.
This was not the case with Sars, which originated in China and killed nearly 800 people globally in 2002 and 2003.
A clinical trial is underway using anti-HIV drugs Ritonavir and Lopinavir to treat patients infected with the new virus, according to a separate article published in The Lancet on Friday.
Beijing's municipal health commission said on Sunday the drugs made by AbbVie Inc are part of the National Health Commission's latest treatment plan, and its hospitals have supplies of the medicine if needed.