NEW YORK, Dec 30 (Reuters) - Transportation agencies across the U.S. are suspending or reducing service due to COVID-19 staff shortages as the Omicron variant surges nationwide. New York"s Metropolitan Transportation Authority (MTA)suspended three New York City subway lines this week - one on Wednesday and two others on Thursday - due to understaffing, though all stations remain open, according to MTA spokesperson Aaron Donovan. The MTA suspended lines that service four of the city"s five boroughs - the Bronx, Brooklyn, Manhattan and Queens, including the W line, which was suspended on Wednesday and continued to be suspended on Thursday, when the MTA also cut B and Z line services. For the second day in a row, the United States had a record number of new reported cases based on the seven-day average, with more than 290,000 new infections reported each day, a Reuters tally showed, as U.S. officials weigh the impact of the more transmissible Omicron variant. read more In Ohio, the Greater Cleveland Regional Transit Authority (RTA) has been able to maintain service despite increased COVID-19 cases among employees, but staff shortages forced a reduction in the frequency of trains on its rapid lines this week. Instead of the normal frequency of trains every 15 to 30 minutes, the frequency has been bumped to 45 minutes to an hour, RTA spokesperson Linda Krecic said. "We"ve been working carefully to make sure we"re able to keep to our schedules," Krecic said, adding that ridership has remained high in recent weeks despite Omicron concerns. In Southern California, crew shortages at Metrolink, the regional passenger rail system, forced the agency to cancel scheduled early-morning trains departing from a New Year"s Eve event in San Bernardino. Metrolink spokesperson Laurene Lopez said the agency has seen an uptick in COVID-19 cases among employees and contractors this week.