[ti:Experts Wonder Why Coronavirus Cases Drop in India] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]Health experts in India are seeking to find out [00:04.56]what caused a major drop in coronavirus cases in recent months. [00:12.04]New infections had climbed for months across India last year, [00:18.20]but then began falling in September. [00:22.80]Now the country is reporting about 11,000 new cases a day. [00:28.80]That is down from nearly 100,000 during the worst period of the crisis. [00:36.84]Experts studying the virus have suggested many possible explanations [00:43.28]for the sudden drop, which happened in nearly every part of India. [00:50.04]Two possible explanations are that some areas of the country [00:55.40]may have reached “herd immunity” or that Indians [01:00.52]may have some preexisting protection from the coronavirus. [01:07.00]The term herd immunity describes a situation [01:11.92]in which enough people in a population are resistant to a disease [01:17.40]so that it cannot spread. [01:19.88]The Indian government has said it believes the decrease happened, [01:25.44]at least partly, because of mask-wearing across the country. [01:31.76]Wearing a mask in public is a rule in India [01:35.72]and is strongly enforced in some cities. [01:40.16]But experts have noted that virus cases [01:43.72]also dropped in areas where mask-wearing was less common. [01:49.48]Finding out causes for the drop could help officials better control COVID-19, [01:56.64]the disease caused by the coronavirus. [02:00.84]India has reported nearly 11 million COVID-19 cases and over 155,000 deaths. [02:12.20]Dr. Shahid Jameel studies viruses at India’s Ashoka University. [02:19.36]“If we don’t know the reason, you could unknowingly be doing things [02:24.68]that could lead to a flare-up,” he told The Associated Press (AP). [02:30.84]India, like other countries, misses many infections, [02:35.72]and there have been questions about how it counts its virus deaths. [02:42.36]But pressure on the country’s hospitals also dropped in recent months. [02:48.52]This suggests that the virus’ spread is slowing. [02:53.96]Recorded cases reached 9 million in November. [02:58.96]At that time, official information showed that nearly 90 percent [03:04.80]of all critical care beds with ventilators in New Delhi were full. [03:11.08]This week, just 16 percent of those beds were occupied. [03:17.64]Experts believe the drop cannot be the result of COVID-19 vaccines [03:24.00]because India only began giving the injections in January. [03:30.32]They say the effects of the vaccination program will only be seen later. [03:37.32]Vineeta Bal studies how the body fights disease [03:41.52]at India’s National Institute of Immunology. [03:46.92]She told the AP she thinks the drop in virus cases [03:51.60]could be related to large areas reaching herd immunity. [03:57.84]But other experts have warned that even if herd immunity [04:02.60]in some places is partly responsible for the drop, [04:07.48]the population as a whole remains vulnerable. [04:11.60]This means people must continue to take measures to protect themselves. [04:19.48]New research suggests that people who got sick with one form of the virus [04:25.24]may be able to get infected again with a new version. [04:30.44]For example, Bal pointed to a recent study in Manaus, Brazil. [04:36.68]It estimated that over 75 percent of people there [04:41.96]had antibodies for the virus in October [04:45.64]-- before cases saw a sharp rise again in January. [04:51.96]“I don’t think anyone has the final answer,” she said. [04:57.80]Experts say another possibility is that many Indians get exposed [05:04.00]to a series of diseases throughout their lives. [05:08.76]That could help build up immunity against new viruses. [05:14.64]Among diseases common in India are cholera, typhoid and tuberculosis. [05:22.44]“If the COVID virus can be controlled in the nose and throat, [05:27.68]before it reaches the lungs, it doesn’t become as serious,” [05:32.60]said Dr. Jameel of Ashoka University. [05:37.32]“Innate immunity works at this level, [05:40.48]by trying to reduce the viral infection [05:43.76]and stop it from getting to the lungs,” he added. [05:48.80]Even with the major drop in infections, [05:52.12]Indian health officials are worried about new virus versions, [05:57.00]or variants, slowing efforts to fight the coronavirus. [06:02.84]Scientists have identified several new variants in the country, [06:08.16]including some blamed for causing new infections in people [06:12.72]who already had an earlier virus version. [06:17.20]I’m Bryan Lynn. 更多听力请访问51VOA.COM