In a study appearing this week in the journal Science, German virus researchers say they have tentatively determined the structure of a key protein used by the SARS virus to infect cells and believe that the virus would be vulnerable to treatment by a modified version of an experimental common cold drug called AG7088.
On the frontlines of the SARS battle, thousands of people have come out of quarantine in Beijing where SARS infection rates have fallen, but the World Health Organization warned Tuesday the city might yet face a new upsurge and that its migrant workers were carrying the disease into the vulnerable countryside.
In Nigeria, meanwhile, authorities scrambled to screen people for SARS after the death of a Taiwanese man there. And Greek health officials said a 23-year-old flight attendant had been quarantined after she showed SARS symptoms.
More than 7,400 cases of severe acute respiratory syndrome have been reported worldwide and the international death toll stood at least 580 on Tuesday.
China's official Xinhua news agency reported Tuesday that 10,000 Beijing residents were in isolation — down from a peak of about 16,000 last week.
AG7088 is currently in clinical trials for the treatment of rhinovirus, a pathogen that can cause the common cold, according to experts at the journal Science.
Rolf Hilgenfeld of the University of Luebeck in Germany, senior author of the study, said he and his co-authors have developed a model for an enzyme that the SARS virus uses to infect cells. Based on this model, Hilgenfeld said in a statement that AG7088 provides "a good starting point" for developing a drug that will block the ability of the SARS virus to reproduce.
The enzyme, called a protease, is typical of proteins that viruses use to take over a host cell and force that cell to make new virus particles, thus spreading the infection throughout the body. Blocking the protease action would not prevent an initial infection, experts say, but it would prevent the spread of the virus.
Hilgenfeld said the researchers found close similarities between the protease enzyme of rhinovirus and the protein in SARS, which is a type of coronavirus.
Since AG7088 is effective against rhinovirus, he said, then a modified version of the drug might inhibit the action of the SARS virus enzyme.
In Singapore, determined authorities proved that no visitor is immune from SARS screening. German Chancellor Gerhard Schroeder filled out a health declaration form and was checked out by thermal imaging camera after he touched down at Changi airport as part of Southeast Asian tour.
Also Tuesday, Hong Kong mourned the death of its first doctor from SARS and Japan shipped 3,000 masks to its citizens in Taiwan, where 13 new SARS cases were announced.
More than 7,400 cases of severe acute respiratory syndrome have been reported worldwide and the international death toll stood at least 561.
SARS fears, meanwhile, made a giant leap — to the continent of Africa.
Nigeria was screening visitors for signs of the disease after a Taiwanese businessman died of suspected SARS. Health officials in the west African nation believed the man — who died Feb. 28 — had been in contact with about 30 Nigerians in Kano and Lagos.
All were placed under medical surveillance and six developed "flu-like symptoms" but fully recovered, Nigeria's health minister, Alphonsus Nwosu, said.
With a population of more than 126 million, Nigeria is Africa's most populous country. Health experts fear the world's poorest continent — which has minimal health care and millions already weakened by AIDS — would face devastating consequences from a SARS epidemic.
Underscoring its concerns about SARS, Nigeria canceled plans to play in the Kirin Cup 2003 soccer tournament in Japan next month. Nigeria was chosen as a replacement for Portugal, which also pulled out because of the SARS scare.
A doctor in Hong Kong became the latest SARS death. Dr. Tse Yuen-man died Tuesday at Tuen Mun Hospital, where she contracted SARS while treating patients with a nurse who also died last week.
The flu-like illness has hit health workers hard. In China, state-run media has lauded them as "angels in white."
Authorities in Beijing have lifted SARS quarantines on three hospitals and a residential neighborhood, cutting the number of people isolated in the Chinese capital to 10,017, Xinhua said Tuesday.
Beijing's newly reported cases of SARS has been declining in recent days while authorities step up efforts to keep its from spreading to China's impoverished countryside.
China, which is creating its first national headquarters for health emergencies, has told provincial officials to set up their own disease-reporting networks. The lack of such a system has been blamed in part for China's slow response to SARS.
SARS has killed at least 252 people on China's mainland, and number of people infected has passed 5,000.
WHO experts are visiting the poor southern region of Guangxi to look at the possible spread of the virus by migrant workers. Another WHO team returned Monday to Beijing after studying a surge in cases in the densely populated neighboring province of Hebei.